Annual epidemiological commentary: Gram-negative, MRSA, MSSA bacteraemia and C. difficile infections, up to and including financial year 2024 to 2025

Question 1

Main points

Accepted Answer

Main messages for each infection are:

Escherichia coli (E. coli) bacteraemia

the incidence rate of Escherichia coli (E. coli) bacteraemia increased by 17.0% between financial year (FY) 2020 to 2021 and FY 2024 to 2025 to 76.6 cases per 100,000 population following the decline observed during the COVID-19 pandemic, returning to levels comparable to those seen in FY 2018 to 2019
these rises were primarily due to community-onset (CO) cases, which represented 80.8% of cases in FY 2024 to 2025

Klebsiella species (spp.) bacteraemia

Klebsiella species (spp.) bacteraemia rates have been increasing year-on-year since surveillance began
the incidence rate increased by 2.9% since FY 2023 to 2024 to 23.6 cases per 100,000 population, caused predominantly by CO cases

Pseudomonas aeruginosa (P. aeruginosa) bacteraemia

Pseudomonas aeruginosa (P. aeruginosa) bacteraemia rates remained stable when compared with the previous year, with an overall rate of 7.8 cases per 100,000 population, and a hospital-onset (HO) rate of 4.8 per 100,000 overnight bed-days

MRSA bacteraemia

Meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia rates in FY 2024 to 2025 increased by 29.5% to 1.9 cases per 100,000 population after a sustained period of stability ended in FY 2018 to 2019
the most recent rate exceeded that seen in the last 12 years, and is the largest annual increase (17.4%) in MRSA rates since surveillance began
HO and CO cases in both the hospital and community setting have contributed to the rise seen over the last 7 years. Since FY 2018 to 2019, CO rates increased by 27.8% and HO rates increased by 29.2%

MSSA bacteraemia

the meticillin-sensitive Staphylococcus aureus (MSSA) bacteraemia rate exceeded pre-COVID-19-pandemic levels, reaching 24.2 cases per 100,000 population, a 12.0% increase compared with FY 2018 to 2019
recent increases were caused by an increase in the rate of CO cases

Clostridioides difficile infection (CDI)

Clostridioides difficile infection (CDI) cases have increased since FY 2020 to 2021, with the rate increasing by 49.8% to 33.3 cases per 100,000 population
this marks the highest incidence rate since FY 2011 to 2012 and has been caused by recent increases in both HO and CO CDI cases

Main messages for ethnicity, deprivation and mortality are:

Black and Asian ethnic groups showed some of the highest age-standardised incidence in E. coli, Klebsiella spp., P. aeruginosa, MRSA and MSSA, in contrast to CDI, where the White ethnic group had the highest standardised incidence. Age-standardised incidence rates varied significantly, with some ethnic groups experiencing rates 2.4 to 4.4 times higher than other groups across the organisms
deprivation analyses showed differences in age-sex standardised rates: where the rate in the most deprived group was 1.5 to 3.1 times higher than the least deprived group across all infections
since FY 2023 to 2024, the 30-day case-fatality rate decreased or remained stable across all infections, except MSSA, where it increased by 5.2%. The 30-day mortality rate rose across most infections and to a lesser extent for Klebsiella spp. (1.5%) whilst P. aeruginosa remained stable

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Epidemiological analysis of Gram-negative organisms: Escherichia coli bacteraemia

Total reports

A total of 43,639 cases of E. coli bacteraemia were reported by NHS acute trusts in England in FY 2024 to 2025, of which 8,397 (19.2%) were hospital-onset (HO) cases (Table S1 in the accompanying data). The total reported cases from FY 2024 to 2025 increased by 3.3% compared to the previous FY 2023 to 2024 (n = 42,246). Over time E. coli rates have increased consistently from FY 2012 to 2013, except for the rate decrease during the COVID-19 pandemic (2020 to 2022).

From FY 2012 to 2013 cases have increased overall by 35.1% (from 32,309 to 43,639 cases) and the incidence rate increased from 60.4 to 76.6 cases per 100,000 population (Figure 2).

This most recent FY sees overall rates still slightly below pre-pandemic levels but higher than the start of surveillance.

Figure 1. Trends in the rate of E. coli bacteraemia, England, by financial year: April 2012 to March 2025

Note: shaded bands indicate 95% confidence intervals (CIs)

Hospital and community-onset cases

Community-onset (CO) rates (cases per 100,000 population) increased year-on-year from 46.3 to 63.7 between FY 2012 to 2013 and FY 2018 to 2019 (Figure 1 and Table 1). Following this increase, CO rates declined for the first time between FY 2019 to 2020 and FY 2020 to 2021, reaching 53.8, coinciding with the beginning of the COVID-19 pandemic, and have since increased to 61.8 in FY 2024 to 2025. This increase was also reflected in episode counts, with 35,242 CO cases reported in FY 2024 to 2025, just below the counts seen before the pandemic.

In contrast, the HO (hospital-onset) rate (cases per 100,000 bed-days) of E. coli cases was relatively stable at around 22.0 between FY 2012 to 2013 and FY 2018 to 2019 apart from a temporary decrease to 21.1 in FY 2014 to 2015 (Table 1). Rates continued to increase from FY 2018 to 2019 to FY 2020 to 2021 (22.1 to 23.6), then declined to 21.5 the following year, but have steadily increased since, reaching 23.2 in FY 2024 to 2025, surpassing FY 2018 to 2019 levels.

Figure 2. Monthly counts of E. coli bacteraemia by onset of infection, England, by financial year: April 2012 to March 2025

Table 1. E. coli bacteraemia counts and rates, England, by financial year: April 2012 to March 2025

Financial year [note 1]	Mid-year population estimate [note 2]	All reported cases	Rate (all reported cases per 100,000 population)	Total bed-days	Hospital-onset cases	Rate (hospital-onset per 100,000 bed-days)	Community-onset cases	Rate (community-onset per 100,000 population)
2012 to 2013	53,498,224	32,309	60.4	34,633,855	7,552	21.8	24,757	46.3
2013 to 2014	54,030,048	34,286	63.5	34,514,871	7,558	21.9	26,728	49.5
2014 to 2015	54,478,406	35,823	65.8	34,972,728	7,382	21.1	28,441	52.2
2015 to 2016	55,040,935	38,315	69.6	34,752,604	7,744	22.3	30,571	55.5
2016 to 2017	55,256,716	40,690	73.6	35,148,014	7,890	22.4	32,800	59.4
2017 to 2018	55,694,748	41,152	73.9	34,903,075	7,688	22.0	33,464	60.1
2018 to 2019	55,999,864	43,290	77.3	34,538,184	7,632	22.1	35,658	63.7
2019 to 2020	56,369,653	43,410	77.0	34,637,156	7,839	22.6	35,571	63.1
2020 to 2021	56,266,460	36,819	65.4	27,628,155	6,530	23.6	30,289	53.8
2021 to 2022	56,692,394	38,050	67.1	32,905,086	7,085	21.5	30,965	54.6
2022 to 2023	57,112,542	38,789	67.9	35,490,766	7,885	22.2	30,904	54.1
2023 to 2024	57,230,111	42,246	73.8	35,991,392	8,171	22.7	34,075	59.5
2024 to 2025	56,994,974	43,639	76.6	36,195,302	8,397	23.2	35,242	61.8

Note 1: financial year ranges from April of one year to March of the following year.

Note 2: Office for National Statistics (ONS) mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Seasonal trends in E. coli bacteraemia

Seasonality was assessed as the number of cases each quarter as a percentage of total cases for the financial year. This analysis was performed separately for hospital-onset and community-onset cases (Table S7 in the accompanying data). In general, community-onset E. coli cases peak in the July to September quarter of every year (for example, summer), a trend that has not changed since April 2012. Historically, there was much less seasonal variation in hospital-onset E. coli cases. However, in FY 2020 to 2021, hospital-onset E. coli cases peaked in October 2020 to December 2020 and January 2021 to March 2021. This was compared with previous years, where it peaked in the July to September quarter. These variations to seasonal trends occurred during the second wave of COVID-19.

Prior trust exposure

In comparison to FY 2020 to 2021, in FY 2024 to 2025 there was an increase in the total count of hospital-onset healthcare-associated (HOHA) E. coli counts from 6,530 to 8,397, with the incidence rate showing a slight decrease from 23.6 to 23.2 cases per 100,000 bed-days. Contributing factors include a slow increase in bed occupancy since the COVID-19 pandemic.

Over the same period, both the count and rate of community-onset healthcare-associated (COHA) E. coli bacteraemia counts increased by 22.4% (from 5,127 to 6,277) and rates decreased by 7.7% (from 16.9 to 15.6 cases per 100,000 bed-days and day admissions), respectively.

Increases were seen in both the counts and rates of community-onset community-associated (COCA) cases, for the same period, from 24,816 to 28,938 cases (an increase of 16.6%) and from 44.1 to 50.8 (an increase of 15.1%) cases per 100,000 population, respectively (Table S8 in the accompanying data).

Since FY 2020 to 2021 the distribution of cases by prior trust distribution has remained stable. In FY 2024 to 2025, 66.3% of cases were COCA, 14.4% COHA and 19.2% HOHA (Figure 3). Caution is advised when comparing with FY 2019 to 2020 prior trust exposure distribution for community-onset cases within Table S8 in the accompanying data. During this period, the number reported with no information on prior trust exposure was 5,153; however, subsequently when the relevant fields became mandatory from late 2019, this resulted in a sharp decline in missing data, with sporadic counts ranging from zero to 2 in subsequent years.

Figure 3. Proportion of prior trust exposure of E. coli bacteraemia cases, England, by financial year, April 2020 to March 2025

Age and sex distribution

Broadly, the age and sex distribution of E. coli cases in FY 2012 to 2013, at the start of surveillance, versus FY 2024 to 2025 of cases was similar (Figure 4 and Table S2 in the accompanying data) . The greatest burden of infection remains in adults aged 45 years and over; within this demographic, male and female cases aged 75 to 84 years have the highest proportion of cases, comprising 16.2% of male and 14.1% of female total cases (FY 2024 to 2025), respectively.

The percentage distribution of cases amongst male and female cases were similar across age groups, except in those aged 15 to 44 years, where cases were approximately 3 times higher in female cases compared to male cases in both presented financial years. For all age and sex analyses, cases for which the sex or age was missing or reported as ‘unknown’ were excluded.

Figure 4. Age and sex distribution of E. coli bacteraemia by percentage of cases, England, by financial years: April 2012 to March 2013 and April 2024 to March 2025

The incidence rate increased in most age groups, for male and female cases between FY 2012 to 2013 and FY 2024 to 2025.

In FY 2024 to 2025, both male and female cases had the highest rates amongst individuals aged 85 years and over at 895.7 and 578.5 cases per 100,000 population, respectively. In this period, the rate ratio between men and woman consistently increased with age in all those age groups containing individuals aged 45 years and over. This was also consistent with FY 2012 to 2013.

Compared to the last financial year, FY 2024 to 2025 displayed a 19.7% decline in infection rates for male cases in the under one year age group and a 22.8% increase for female cases. There was a slight increase in rates in those aged 45 years and over for both male and female cases (Figure 5).

In the last 4-year period post-pandemic (from April 2021 to March 2025), the rate in male cases aged 85 years and over increased by 12.1% from 798.8 to 895.7 cases per 100,000 population. The rate amongst those aged 75 to 84 years increased by 13.5%, from 366.9 to 416.2 cases per 100,000 population.

During the same post-pandemic period between FY 2021 to 2022 and FY 2024 to 2025, increases were also observed in female cases, in the 85 years and over age group, an increase of 13.0% was observed, rising from 512.1 to 578.5 cases per 100,000 population. Similarly, those aged 75 to 84 years displayed an increase of 15.6% since FY 2021 to 2022 (264.1 to 305.2).

All other age groups showed varying degrees of fluctuation but remained relatively low (less than 200.0 cases per 100,000 population) in FY 2024 to 2025.

Figure 5. Trends in age group and sex rates of E. coli bacteraemia, England, by financial year: April 2012 to March 2025

Note: shaded bands indicate 95% CIs.

The rates of E. coli bacteraemia broadly increased between FY 2012 to 2013 and FY 2018 to 2019. This was followed by a large decline between the April 2020 and March 2021 period due to the pandemic. In FY 2024 to 2025, there was an increase in rate in most age groups and in both male and female cases. The highest increase in rate, when compared to FY 2023 to 2024, was in male cases (7.1%) aged 45 to 64 years, while female cases in this age group showed a 1.5% rise in rates. This was followed by those aged 65 to 74 years, with increases of 6.3% in male cases and 4.8% in female cases.

Caution is advisable when interpreting data for E. coli amongst those aged 1 to 14 years as the number of cases is too small to interpret trends well.

Cases with missing age or sex was rare and reduced over the surveillance period, with 51 cases in FY 2012 to 2013, versus 2 cases in FY 2024 to 2025.

Trends by ethnicity

In FY 2024 to 2025, the observed incidence rate of E. coli bacteraemia was highest in the White ethnic group (79.2 cases per 100,000 population), followed by the Asian and Black ethnic groups (56.6 and 53.0 cases per 100,000 population, respectively) (Figure 6 and Table S14 in the accompanying data) . It was lowest in the Other and Mixed ethnic groups (20.4 and 18.9 cases per 100,000 population, respectively).

The age-standardised incidence rate saw the highest incidence rates in the Asian and Black ethnic groups (118.4 and 96.6 cases per 100,000 population, respectively) versus the White ethnic group (71.6 cases per 100,000 population). Rates in the Asian and Black ethnic groups increased sharply year-on-year from FY 2020 to 2021. In FY 2024 to 2025, Asian, Black and Other ethnic groups experienced the highest age-standardised rates of E. coli bacteraemia since April 2017.

Figure 6. E. coli bacteraemia rate by ethnicity, England, by financial year: April 2018 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by deprivation

In FY 2024 to 2025, 82.2 cases occurred per 100,000 people living in the 20% most deprived areas versus 68.3 cases per 100,000 people living in the 20% least deprived areas (Figure 7 and Table S13 in the accompanying data). The observed incidence rate of E. coli bacteraemia generally increased with deprivation.

The variation in age-sex standardised incidence rates of E. coli was much greater or lower than that observed (100.4 and 56.4 cases per 100,000 population) in the 20% most or 20% least deprived areas, respectively, suggesting the risk is doubled between these 2 indices of multiple deprivation (IMD) quintiles. Also noted is that the gap between the various deprivation levels is much wider for age-sex standardised data even though the ranking does not necessarily change. All IMD quintiles have seen increases in age-sex standardised rates in the last financial year. There has been a consistent ordering of age-sex standardised E. coli time series by increasing deprivation since April 2017.

Figure 7. E. coli bacteraemia rate by deprivation, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Primary focus of E. coli bacteraemia

The provision of data on the most likely primary focus of E. coli bacteraemia is voluntary. The percentage of cases where this information has been provided has declined over time from 85.5% (n = 27,610) in FY 2012 to 2013 to 49.7% (n = 21,707) in FY 2024 to 2025 (Table 2), with a 1.2% decrease versus FY 2023 to 2024 (n = 21,981) (Table S4 in the accompanying data).

Of cases with a reported primary focus of infection, urinary tract has consistently been the most frequent primary focus for E. coli bacteraemia cases. In FY 2012 to 2013 48.9% of cases reported a most likely primary focus of urinary tract, and by FY 2024 to 2025, 46.3% (n = 10,056). Hepatobiliary as a primary focus has slightly increased between FY 2012 to 2013 and FY 2024 to 2025 from 13.6% to 15.7%. The percentage of records for which the primary focus was reported as unknown has decreased from 20.2% in FY 2012 to 2013 to 17.5% in FY 2024 to 2025. All other reported primary focus rates have remained relatively unchanged between FY 2012 to 2013 and FY 2024 to 2025 apart from a change from 3.8% to 6.1% for respiratory tract.

Table 2. E. coli bacteraemia counts and percentages by primary focus of bacteraemia, England, by financial year: April 2012 to March 2025

Financial year [note 1]	Total E. coli reported	Primary focus ascertained: (number)	Primary focus ascertained: (%)	Gastro-intestinal [note 2]: (number)	Gastro-intestinal (% [note 2])	Hepatobiliary: (number)	Hepatobiliary: (%)	Urinary tract: (number)	Urinary tract: (%)	Respiratory tract: (number)	Respiratory tract: (%)	Other [note 3] : (number)	Other (% [note 3])	Unknown: (number)	Unknown (%)
2012 to 2013	32,309	27,610	85.5%	1,782	6.5%	3,756	13.6%	13,501	48.9%	1,050	3.8%	1,936	7.0%	5,585	20.2%
2013 to 2014	34,286	28,300	82.5%	1,711	6.0%	3,855	13.6%	13,393	47.3%	1,016	3.6%	1,873	6.6%	6,452	22.8%
2014 to 2015	35,823	28,729	80.2%	1,640	5.7%	3,818	13.3%	13,088	45.6%	1,099	3.8%	1,851	6.4%	7,233	25.2%
2015 to 2016	38,315	26,446	69.0%	1,492	5.6%	3,556	13.4%	12,220	46.2%	1,068	4.0%	1,703	6.4%	6,407	24.2%
2016 to 2017	40,690	22,727	55.9%	1,237	5.4%	3,277	14.4%	10,727	47.2%	1,028	4.5%	1,553	6.8%	4,905	21.6%
2017 to 2018	41,152	25,616	62.2%	1,717	6.7%	4,035	15.8%	12,566	49.1%	1,575	6.1%	1,757	6.9%	3,966	15.5%
2018 to 2019	43,290	28,469	65.8%	1,969	6.9%	4,687	16.5%	13,914	48.9%	1,728	6.1%	1,989	7.0%	4,182	14.7%
2019 to 2020	43,410	27,515	63.4%	1,774	6.4%	4,351	15.8%	13,241	48.1%	1,674	6.1%	1,898	6.9%	4,577	16.6%
2020 to 2021	36,819	20,395	55.4%	1,352	6.6%	3,721	18.2%	8,972	44.0%	1,251	6.1%	1,524	7.5%	3,575	17.5%
2021 to 2022	38,050	18,636	49.0%	1,328	7.1%	3,108	16.7%	8,393	45.0%	1,092	5.9%	1,489	8.0%	3,226	17.3%
2022 to 2023	38,789	18,448	47.6%	1,268	6.9%	2,859	15.5%	8,316	45.1%	1,053	5.7%	1,597	8.7%	3,355	18.2%
2023 to 2024	42,246	21,981	52.0%	1,404	6.4%	3,400	15.5%	9,892	45.0%	1,280	5.8%	1,907	8.7%	4,098	18.6%
2024 to 2025	43,639	21,707	49.7%	1,503	6.9%	3,408	15.7%	10,056	46.3%	1,315	6.1%	1,621	7.5%	3,804	17.5%

Note 1: financial year from April to March of the following year.

Note 2: gastrointestinal (not hepatobiliary).

Note 3: ‘Other’ includes the following options inputted on the HCAI DCS: bone and joint, central nervous system, genital tract (including prostate), indwelling intravascular device, other, respiratory tract, skin or soft tissue, no clinical signs of bacteraemia.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, the primary focus of E. coli bacteraemia also varied according to time-to-onset (duration between hospital admission and date of a positive specimen) (Table 3). Urinary tract as the primary focus was the most reported amongst time to-onset-groups. Furthermore, urinary tract as a primary focus was more common in cases where the time-to-onset was less than 2 days (49.3%) versus 2 and 6 days (33.8%) and 7 days or greater (37.6%).

Table 3. Distribution of primary focus E. coli bacteraemia, by time-to-onset, England, by financial year: April 2024 to March 2025

Time to onset (days) [note 1]	Gastrointestinal (not hepatobiliary) (number)	Gastrointestinal (not hepatobiliary) (%) [note 2]	Hepatobiliary (number)	Hepatobiliary (%) [note 2]	Urinary tract (number)	Urinary tract (%) [note 2]	Respiratory tract (number)	Respiratory tract (%) [note 2]	Other (number)	Other (%) [note 2]
Less than 2	540	6.3%	1,405	16.3%	4,238	49.3%	377	4.4%	575	6.7%
2 to 6	200	13.0%	314	20.3%	522	33.8%	78	5.1%	152	9.9%
7 and over	349	11.5%	362	11.9%	1,143	37.6%	192	6.3%	420	13.8%

Note 1: number of days from admission to positive bacteraemia sample (if both are on the same date the difference would be zero days).

Note 2: proportion of cases by primary focus.

Geographic distribution

The crude and age-sex standardised rates is presented across integrated care boards (ICBs) for FY 2024 to 2025, of which there was considerable geographical variation in rates of E. coli bacteraemia (Figure 8). Age-sex standardised rates (cases per 100,000 population) indicate high incidence in London, Northern and Midlands regions, specifically North-East London ICB (107.1), South Yorkshire ICB (99.0), Frimley ICB (97.8) and Nottingham and Nottinghamshire ICB (96.0) (Table S6 in the accompanying data). The lowest incidence rates were observed in Gloucestershire ICB (32.2), Bath and North-East Somerset, Swindon and Wiltshire ICB (56.5) and Herefordshire and Worcestershire ICB (58.1).

Figure 8. Geographic distribution of E. coli bacteraemia rate, by Integrated Care Boards, England, by financial year: April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Mortality

In FY 2024 to 2025, 43,639 E. coli bacteraemia cases were reported in England. Information on mortality was available for 99.1% (43,233) of these cases (Table S9 in the accompanying data). There were 6,342 deaths within 30 days of an E. coli bacteraemia diagnosis, a mortality rate of 11.1 deaths per 100,000 population and a case-fatality rate (CFR) of 14.6% (Figure 9).

Similar to previous reports, there was a declining trend in CFR from the beginning of surveillance (FY 2012 to 2013, CFR: 16.8%), until FY 2018 to 2019 (CFR: 13.8%), after which the CFR increased to 16.1% by FY 2020 to 2021. Over the past 4 years, the CFR trend has fluctuated, with a marginal decline over the last 2 years, resulting in a current CFR of 14.6% for FY 2024 to 2025. The mortality rate increased slightly between FY 2023 to 2024 and FY 2024 to 2025, rising from 10.7 to 11.1 deaths per 100,000 population, contrasting with the slight decrease observed in the previous year.

Figure 9. Case-fatality rate and mortality rate of E. coli bacteraemia, England, by financial year: April 2012 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Variation by onset of bacteraemia

Following the decline observed in FY 2021 to 2022 when community-onset (CO) mortality rate was 7.2, mortality rate has since increased to 7.9 deaths per 100,000 population (Table S11 in the accompanying data). Hospital-onset (HO) rates increased from 4.9 to 5.1 deaths per 100,000 population during the same period.

Both HO CFR and CO CFR saw modest declines between FY 2012 to 2013 and FY 2024 to 2025, with HO CFR decreasing from 23.6 to 21.9% and CO CFR from 14.8 to 12.8%. The HO CFR remained 1.5 to 1.8 times higher than CO CFR throughout the period.

Variation by age and sex

In FY 2024 to 2025, amongst male cases, the highest mortality rates were observed in those aged 85 years and over (208.5 deaths per 100,000 population) and aged 75 to 84 years (68.6 deaths per 100,000 population) (Table S10 in the accompanying data). This equated to CFRs of 23.3% and 16.5%, respectively, indicating a slight increase in those aged 85 years and over but a decrease in those aged 75 to 84 years from the previous FY 2023 to 2024 which recorded CFRs of 22.8% and 17.2%, respectively. The mortality rate for both groups increased by 7.8% and 0.3%, from the previous year, respectively.

Similar to male cases, the highest mortality rates in female cases in FY 2024 to 2025 was seen in those aged 85 years and over at 104.5 deaths per 100,000 population, followed by those aged 75 to 84 years at 42.6. This equated to CFRs of 18.1% and 14.0% of cases, respectively.

Numbers of deaths are small in some of the younger groups so differences should be interpreted with caution.

Variation by region

Case-fatality rates in FY 2024 to 2025 were broadly similar across the country, being highest in the Midlands region (16.1%) followed by East of England (14.9%) and North West (14.9%) (Table S12). The CFR remained lowest in London (12.6%), the South West (13.6%) and South East of England (14.3%).

Epidemiological analysis of Gram-negative organisms: Klebsiella spp. bacteraemia

Total reports

A total of 13,438 cases of Klebsiella species (Klebsiella spp.) bacteraemia were reported by NHS acute trusts in England in FY 2024 to 2025, an increase of 2.5% from FY 2023 to 2024 (n = 13,111), marking a steady annual increase in cases since the substantial 10.5% rise between FY 2022 to 2023 and FY 2023 to 2024 (Table S1 in the accompanying data). Of these, 4,185 (31.1%) were hospital-onset cases (Figure 11). The total count of Klebsiella spp. bacteraemia has increased year-on-year since the start of surveillance (FY 2017 to 2018) from 9,823 to 13,438. This increase was also reflected in the incidence rate of total Klebsiella spp. bacteraemia cases, which increased from 17.6 cases per 100,000 population in FY 2017 to 2018 to 23.6 in FY 2024 to 2025.

Figure 10. Trends in the rate of Klebsiella spp. bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Hospital and community-onset cases

Community-onset rates (CO) have increased from 12.4 cases per 100,000 population in FY 2017 to 2018 to 14.0 in FY 2019 to 2020 (Figure 10 and Table 4). Following this increase, CO rates declined in FY 2020 to 2021, reaching 13.2. Since then, CO counts and rates have seen a rapid increase, increasing from 7,917 and 13.9 in FY 2022 to 2023 to 9,123 and 15.9 in FY 2023 to 2024, respectively. This upward trend has continued for FY 2024 to 2025, maintaining a steady increase to 9,253 and 16.2.

The rate (cases per 100,000 bed-days) of hospital-onset (HO) Klebsiella spp. cases was 8.4 in FY 2017 to 2018 increasing to 13.8 by FY 2020 to 2021. This observed increase has 2 components. Firstly, the number of HO cases increased from 3,233 to 3,803 between April 2019 and March 2021. Secondly, there was a drop off in hospital activity (occupied bed-days) between April 2019 and March 2021 which resulted in increased rates.

Hospital activity has since increased, contributing to the decrease in HO rate to 11.3 in FY 2021 to 2022 and 11.1 in FY 2023 to 2024, despite an increase in case numbers. The rate for FY 2024 to 2025 was 11.6, a minor increase compared to the previous year.

Figure 11. Monthly counts of Klebsiella spp. bacteraemia by onset of infection, England, by financial year: April 2017 to March 2025

Table 4. Klebsiella spp. bacteraemia counts and rates, England, by financial year: April 2017 to March 2025

Financial year [note 1]	Mid-year population estimate [note 2]	All reported cases	Rate (all reported cases per 100,000 population)	Total bed-days	Hospital-onset cases	Rate (hospital-onset cases per 100,000 bed-days)	Community-onset cases	Rate (community-onset cases per 100,000 population)
2017 to 2018	55,694,748	9,823	17.6	34,903,075	2,937	8.4	6,886	12.4
2018 to 2019	55,999,864	10,739	19.2	34,538,184	3,217	9.3	7,522	13.4
2019 to 2020	56,369,653	11,097	19.7	34,637,156	3,233	9.3	7,864	14.0
2020 to 2021	56,266,460	11,204	19.9	27,628,155	3,803	13.8	7,401	13.2
2021 to 2022	56,692,394	11,452	20.2	32,905,086	3,711	11.3	7,741	13.7
2022 to 2023	57,112,542	11,865	20.8	35,490,766	3,948	11.1	7,917	13.9
2023 to 2024	57,230,111	13,111	22.9	35,991,392	3,988	11.1	9,123	15.9
2024 to 2025	56,994,974	13,438	23.6	36,195,302	4,185	11.6	9,253	16.2

Note 1: financial year ranges from April of one year to March of the following year.

Note 2: ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Seasonal trends

The seasonal trends in hospital-onset and community-onset cases in FY 2024 to 2025, was similar to that seen before the pandemic (FY 2017 to 2018 and FY 2020 to 2021). Across hospital-onset, community-onset and all cases, the percentage of yearly infections was generally higher during the July to September quarter, and lower in the last 2 financial quarters (Table S7 in the accompanying data).

Distribution of Klebsiella species

In FY 2024 to 2025 Klebsiella pneumoniae (75.1%) was the most frequently reported species, followed by Klebsiella oxytoca (15.4%). This distribution was similar regardless of onset of infection (Table 5). Compared with FY 2023 to 2024, the largest rise in Klebsiella spp. was seen in Klebsiella pneumoniae (4.7%). This is notably lower than the 12.0% increase seen in FY 2023 to 2024 compared to FY 2022 to 2023, marking a slowdown in the rate of increase in the latest year.

Table 5. Counts and percentages of Klebsiella species bacteraemia, England, by financial year: April 2024 to March 2025

Species	All cases	Proportion of all cases	Hospital-onset cases	Proportion of all cases (hospital-onset)	Community-onset cases	Proportion of all cases (community-onset)
K. pneumoniae	10,095	75.1%	3,100	30.7%	6,995	69.3%
K. oxytoca	2,064	15.4%	616	29.8%	1,448	70.2%
K. aerogenes	505	3.8%	235	46.5%	270	53.5%
Other named species	443	3.3%	130	29.3%	313	70.7%
Not speciated	331	2.5%	104	31.4%	227	68.6%

Prior trust exposure

Between FY 2020 to 2021 and FY 2024 to 2025 there was an increase in the count of hospital-onset healthcare-associated (HOHA) cases, from 3,803 to 4,185, but a drop in the HOHA incidence rate, from 13.8 cases per 100,000 bed-days to 11.6 (Table S8 in the accompanying data).

Community-onset healthcare-associated (COHA) Klebsiella spp. cases have remained broadly similar to HOHA cases since FY 2020 to 2021: an increase was observed in FY 2024 to 2025 with counts reaching 1,995, a 32.1% increase from FY 2020 to 2021 and 4.0% from the previous financial year (FY 2023 to 2024). The rate of COHA cases fell slightly by 0.4% from 5.0 to 5.0 cases per 100,000 bed-days and day-admissions compared to FY 2020 to 2021.

Between FY 2020 to 2021 and FY 2024 to 2025, the number of cases and rate of community-onset community-associated (COCA) Klebsiella spp. bloodstream infection (BSI) incidence increased on average annually, respectively, by 6.0% (from 5,839 to 7,246) and by 5.6% (from 10.4 to 12.7 cases per 100,000 population). This increase is more notable between FY 2022 to 2023 and FY 2023 to 2024, when the count and rate increased by 14.8% and 14.5% from 6,246 to 7,168 and 10.9 to 12.5, respectively. For FY 2024 to 2025 the count and rate increase from the previous year saw a slowdown to 1.1% (from 7,168 to 7,246) and 1.5% (from 12.5 to 12.7), respectively.

Since FY 2020 to 2021 the distribution of cases by prior trust distribution has seen small changes in COCA cases from 52.1% to 53.9% and COHA cases from 13.5% to 14.8% while HOHA cases have decreased from 33.9% to 31.1% (Figure 12).

These comparisons should be interpreted with caution as FY 2019 to 2020 had 1,009 cases without prior trust exposure data, which became mandatory in late 2019, and therefore may underestimate the proportion of COHA and COCA cases, compared with one case in FY 2020 to 2021 and zero cases in subsequent years.

Figure 12. Proportion of prior trust exposure of Klebsiella spp. cases, England, by financial year, April 2020 to March 2025

Age and sex distribution

For all age and sex analyses, cases in which the age and/or sex was missing or recorded as unknown were excluded. In FY 2017 to 2018, only one case was reported with ‘unknown’ age or sex versus zero cases of ‘unknown’ age or sex in FY 2024 to 2025 (Table S2 in the accompanying data).

Broadly, the age and sex distribution of Klebsiella spp. bacteraemia cases as a percentage of all reported cases in FY 2017 to 2018 compared to FY 2024 to 2025 remains similar, with most of the burden of infection being amongst male cases (Figure 13). In FY 2024 to 2025, the case burden remained highest in male cases aged 45 years and over, predominantly amongst those aged 75 to 84 years (19.3% of total cases). A similar trend was seen in older female cases aged 45 to 64 years (9.2% of total cases) and aged 75 to 84 years (8.9% of total cases), but to a much lesser extent. This is consistent with what has been observed in FY 2017 to 2018.

Figure 13. Age and sex distribution of Klebsiella spp. bacteraemia by percentage of cases, England, by financial years: April 2017 to March 2018 and April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, the incidence rates of Klebsiella spp. bacteraemia were greater in male cases compared to female cases, particularly amongst those aged 45 years and over. The incidence rate increased in all age groups, for male and female cases, between FY 2017 to 2018 and FY 2024 to 2025.

In FY 2024 to 2025, both male and female cases had their highest rates amongst individuals aged 85 years and over at 297.4 and 88.9 cases per 100,000 population, respectively.

Trends in the age-specific and sex-specific rates of Klebsiella spp. bacteraemia are shown in Figure 14. Rates of Klebsiella spp. bacteraemia have increased across most age and sex groups between the start of the surveillance in FY 2017 to 2018 until FY 2019 to 2020. These increases were notable in male cases aged 75 years and over, and to a lesser extent female cases aged 75 years and over. Sharp declines were observed in these older age groups, in FY 2020 to 2021, which began to increase again in the following financial year. In FY 2024 to 2025, an increase in these older male age groups was noted compared to the previous financial year, increasing by 4.5%, from 146.5 to 153.0 cases per 100,000 population in 75 to 84 years, and by 6.3%, from 279.9 to 297.4 cases per 100,000 population in the 85 years and older group. Unlike male cases aged 85 years and over group, which has seen year-on-year increases in rate since FY 2020 to 2021, female cases in the same age group have seen rates decrease by 7.3%, from 95.8 to 88.9 cases per 100,000 population in FY 2024 to 2025 compared to the previous year. Whereas female cases aged 75 to 84 years, saw an increase by 4.5%, from 56.8 to 59.3 cases per 100,000 population in FY 2024 to 2025 compared to the previous year.

The incidence rate in those aged under one year declined by 5.6% for female cases and 4.7% for male cases since the previous FY 2023 to 2024. Since last year, there was also a decline in the rate amongst those aged between one to 14 years, with a 9.5% decrease in male cases (from 1.9 to 1.7) but female cases remained the same at 1.4 per 100,000 population.

The numbers remain low for the zero to 14 age groups so interpreting long-term trends should be done with caution. For all age and sex analyses, cases in which the age and/or sex was missing or recorded as unknown were excluded. In FY 2017 to 2018, only one case was reported with ‘unknown’ age or sex versus zero cases of ‘unknown’ age or sex in FY 2024 to 2025.

Figure 14. Trends in age group and sex rates of Klebsiella spp. bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by ethnicity

In FY 2024 to 2025, the observed incidence rate of Klebsiella spp. bacteraemia were highest in the Black and White ethnic groups (24.1 and 23.7 cases per 100,000 population, respectively), intermediate in the Asian ethnic group (18.9 cases per 100,000 population), and lowest in the Mixed and Other ethnic groups (7.5 and 6.9 cases per 100,000 population, respectively) (Figure 15 and Table S14 in the accompanying data).

However, age-standardised incidence rates were substantially higher in those of Black ethnicity (41.5), followed by Asian ethnicity (37.9), whereas incidence rate in the White ethnic group was amongst the lowest (21.5). Since April 2021, there were sharper rises in Black and Asian ethnic groups.

Figure 15. Klebsiella spp. bacteraemia rate by ethnicity, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by deprivation

In FY 2024 to 2025, 26.5 cases occurred per 100,000 people living in the 20% most deprived areas versus 20.4 cases per 100,000 people living in the 20% least deprived areas (Figure 16 and Table S13 in the accompanying data). The observed incidence rate of Klebsiella spp. bacteraemia increased with deprivation.

The range between deprivation quintiles was amplified when age-sex standardised incidence of Klebsiella spp. was used. With the standardised rates, the 20% most and 20% least deprived quintiles had respective rates of 34.8 and 17.0 cases per 100,000 population, the range of these is more than double the range for observed incidence rates. There was a continued rise in incidence rate across IMD quintiles from FY 2022 to 2023 to FY 2024 to 2025, except for the past year where the 40% to 60% quintile saw a more moderate increase. There has been a consistent ordering of age-sex standardised Klebsiella spp. bacteraemia time series by increasing deprivation since April 2018.

Figure 16. Klebsiella spp. bacteraemia rate by deprivation, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Primary focus of Klebsiella spp. bacteraemia

Reporting of primary focus for Klebsiella spp. bacteraemia remains low. In FY 2024 to 2025 the primary focus was reported for 45.4% of all cases (Table 6 and Table S4 in the accompanying data). The most frequently reported primary focus of Klebsiella spp. bacteraemia was the urinary tract, constituting 36.4% of cases with a reported primary focus of infection in FY 2024 to 2025. This percentage has remained broadly consistent since the inception of Klebsiella spp. surveillance in FY 2017 to 2018. Hepatobiliary and respiratory tract as primary foci have decreased between FY 2017 to 2018 and FY 2024 to 2025, from 20.2% to 17.1% and from 9.2% to 9.1%, respectively.

Table 6. Klebsiella spp. bacteraemia counts and rates by primary focus of bacteraemia, England, by financial year: April 2017 to March 2025

Financial year [note 1]	Total Klebsiella spp. reported	Primary focus ascertained: (number)	Primary focus ascertained: (%)	Gastro-intestinal [note 2] : (number)	Gastro-intestinal (% [note 2])	Hepatobiliary: (number)	Hepatobiliary: (%)	Urinary tract: (number)	Urinary tract: (%)	Respiratory tract: (number)	Respiratory tract: (%)	Other [note 3] : (number)	Other (% [note 3])	Unknown: (number)	Unknown (%)
2017 to 2018	9,823	5,113	52.1%	374	7.3%	1,032	20.2%	1,681	32.9%	470	9.2%	603	11.8%	953	18.6%
2018 to 2019	10,739	5,816	54.2%	493	8.5%	1,105	19.0%	1,943	33.4%	585	10.1%	768	13.2%	922	15.9%
2019 to 2020	11,097	6,110	55.1%	484	7.9%	1,222	20.0%	2,056	33.6%	581	9.5%	745	12.2%	1,022	16.7%
2020 to 2021	11,204	5,496	49.1%	410	7.5%	985	17.9%	1,726	31.4%	710	12.9%	693	12.6%	972	17.7%
2021 to 2022	11,452	5,256	45.9%	367	7.0%	939	17.9%	1,729	32.9%	550	10.5%	745	14.2%	926	17.6%
2022 to 2023	11,865	5,304	44.7%	430	8.1%	875	16.5%	1,809	34.1%	466	8.8%	755	14.2%	969	18.3%
2023 to 2024	13,111	6,078	46.4%	435	7.2%	1,010	16.6%	2,109	34.7%	534	8.8%	791	13.0%	1,199	19.7%
2024 to 2025	13,438	6,095	45.4%	472	7.7%	1,045	17.1%	2,219	36.4%	556	9.1%	698	11.5%	1,105	18.1%

Note 1: financial year from April to March of the following year.

Note 2: gastrointestinal (not hepatobiliary).

Note 3: ‘Other’ includes the following options inputted on the HCAI DCS: bone and joint, central nervous system, genital tract (including prostate), indwelling intravascular device, other, respiratory tract, skin or soft tissue, no clinical signs of bacteraemia.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, for inpatients with a time-to-onset of fewer than 2 days, the most common primary focus of bacteraemia was urinary tract (42.4%) (Table 7). As the time between admission and the onset of bacteraemia increases, the percentage of inpatients reporting the urinary tract as the primary focus decreases from 42.4% for those with onset in less than 2 days to 23.6% (for those with onset in 7 days or more).

Amongst those with a time-to-onset of less than 2 days, 6.5% had a respiratory focus and 5.6% had a gastrointestinal focus. These percentages were higher amongst individuals with a time-to-onset of 7 days or more, at 12.4% and 13.9% for respiratory and gastrointestinal focus respectively. Caution is advised when interpreting these numbers due to low counts and annual fluctuations in trend.

Table 7. Distribution of primary focus of Klebsiella spp. bacteraemia, by time-to-onset, England, by financial year: April 2024 to March 2025

Time to onset (days) [note 1]	Gastrointestinal (not hepatobiliary) (number)	Gastrointestinal (not hepatobiliary) (%) [note 2]	Hepatobiliary (number)	Hepatobiliary (%) [note 2]	Urinary tract (number)	Urinary tract (%) [note 2]	Respiratory tract (number)	Respiratory tract (%) [note 2]	Other (number)	Other (%) [note 2]
Less than 2	122	5.6%	445	20.4%	924	42.4%	141	6.5%	200	9.2%
2 to 6	71	12.5%	94	16.6%	163	28.7%	62	10.9%	75	13.2%
7 and over	198	13.9%	145	10.2%	336	23.6%	177	12.4%	291	20.4%

Note 1: number of days from admission to positive bacteraemia sample (if both are on the same date the difference would be zero days).

Note 2: proportion of cases by primary focus.

Geographic distribution

The crude and age-sex standardised rates are presented across ICBs for FY 2024 to 2025 (Figure 17). Like E. coli (Figure 8) there is high spatial variability in Klebsiella spp. rates. The highest age-sex standardised rates were observed in some London ICBs and followed by South Yorkshire ICB (36.9; 33.5; 33.0; 32.0, 31.3 cases per 100,000 population), while the lowest were observed in Gloucestershire ICB (9.2 cases per 100,000 population), Herefordshire and Worcestershire ICB (16.6 cases per 100,000 population) and Cornwall and the Isles of Scilly ICB (17.0 cases per 100,000 population) (Table S6 in the accompanying data).

Figure 17. Geographic distribution of Klebsiella spp. bacteraemia rate, by Integrated Care Boards, England, by financial year: April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Mortality

In FY 2024 to 2025, 13,438 Klebsiella spp. bacteraemia cases were reported in England (Table S9 in the accompanying data). Information on mortality was available for 98.9% (13,294) of these cases. There were 2,531 deaths within 30 days of a Klebsiella spp. bacteraemia diagnosis, giving a mortality rate of 4.4 deaths per 100,000 population and a CFR of 18.9% (Figure 18).

The mortality rate increased from 3.5 to 4.4 deaths per 100,000 population between FY 2017 to 2018 and FY 2024 to 2025. A steeper increase in mortality rate was also observed between FY 2022 to 2023 and FY 2024 to 2025, increasing by 9.5% from 4.1 to 4.4, coinciding with the steep increase in cases observed for the same period. In contrast, the CFR decreased marginally by 6.2% from 20.1% (1,972 deaths) to 18.9% (2,531 deaths) between FY 2017 to 2018 and FY 2024 to 2025. Mortality rate and CFR increased temporarily at the start of the COVID-19 pandemic in FY 2020 to 2021, reaching 4.3 deaths per 100,000 and 21.7%, predominantly caused by hospital-onset (HO) cases. However, they subsequently returned to levels similar to those seen previously, despite an overall upward trend.

Figure 18. Case-fatality rate and mortality rate of Klebsiella spp. bacteraemia, England: financial year April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Variation by onset of bacteraemia

Between FY 2023 to 2024 and FY 2024 to 2025, the mortality rate of HO cases decreased from 2.7 deaths per 100,000 bed-days (980 deaths) to 2.6 (956 deaths) (Table S11 in the accompanying data). Similarly, CFR for HO cases decreased from 24.7% to 22.9%, with some fluctuations observed in the intervening years.

The mortality rate in community-onset (CO) cases increased from 2.7 deaths per 100,000 population (1,526 deaths) in FY 2023 to 2024 to 2.8 (1,576 deaths) in FY 2024 to 2025. The corresponding CFRs increased from 16.8% to 17.1%.

Variation by age and sex

In FY 2024 to 2025, as in previous years, the mortality rate and CFR increased with age, except amongst those aged one year and under, where values were higher than in the one to 14 years age group (Table S10 in the accompanying data). Overall, the mortality rate was higher in male cases, while the CFR was greater in female cases, except in the 15 to 44 years age group, where female cases had a higher CFR.

For male cases, the highest mortality rate was observed in those aged 85 years and over (79.0 deaths per 100,000 population) and those aged 75 to 84 years (31.5 deaths per 100,000 population) with corresponding CFRs of 26.6% and 20.6% of cases, respectively. Compared with FY 2023 to 2024, mortality rates for male cases aged 85 years and over and aged 75 to 84 years increased by 10.6% and 5.1%, respectively.

For female cases, the highest mortality rate was also observed in those aged 85 years and over (24.2 deaths per 100,000 population) and those aged 75 to 84 years (13.3 deaths per 100,000 population). CFRs for these groups were 27.2% and 22.5%, respectively. Compared to FY 2023 to 2024, mortality rates for female cases aged 85 years and over decreased by 19.8% but increased by 12.5% for those aged 75 to 84 years.

Variation by region

Case-fatality rates in FY 2024 to 2025 were highest in the South East (20.8%) followed by North West (20.6%) and Midlands (19.1%) (Table S12 in the accompanying data). The CFR remained lowest in both London (17.1%) and the South West (17.2%).

Epidemiological analysis of Gram-negative organisms: Pseudomonas aeruginosa bacteraemia

Total reports

A total of 4,474 cases of Pseudomonas aeruginosa (P. aeruginosa) bacteraemia were reported by NHS acute trusts in England in FY 2024 to 2025 (Table S1 in the accompanying data). Of the 4,474 P. aeruginosa cases, 1,729 (38.6%) were hospital-onset cases. There was little variation in the counts of total P. aeruginosa cases since the start of enhanced surveillance in 2017, except for a spike in the rate of hospital-onset cases in FY 2020 to 2021 (Figure 20). Since then, the rate has declined and remains stable at 4.8 cases per 100,000 bed-days in FY 2024 to 2025.

Figure 19. Trends in the rate of P. aeruginosa bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Hospital and community-onset cases

The rate (cases per 100,000 bed-days) of P. aeruginosa hospital-onset (HO) cases was stable between FY 2017 to 2018 and FY 2019 to 2020, ranging from 4.4 to 4.7 cases per 100,000 bed-days (Figure 19 and Table 8). This increased to 6.1 in FY 2020 to 2021. The observed increase in rate was due to an increase in the reported number of hospital-onset cases, from 1,583 in FY 2019 to 2020 to 1,675 in FY 2020 to 2021, complicated by a decline in bed-days reported due to the COVID-19 pandemic; the hospital-onset rate reverted back in the following financial years, with a rate of 4.8 in FY 2024 to 2025.

Community-onset (CO) cases comprise 61.4% of all reported P. aeruginosa cases in FY 2024 to 2025. In comparison to HO rates, CO rates have remained stable averaging at 4.8 cases per 100,000 population over the 8 surveillance years.

Figure 20. Monthly counts of P. aeruginosa bacteraemia by onset of infection, England, by financial year: April 2017 to March 2025

Table 8. P. aeruginosa bacteraemia counts and rates, England, by financial year: April 2017 to March 2025.

Financial year [note 1]	Mid-year population estimate [note 2]	All reported cases	Rate (all reported cases per 100,000 population)	Total bed-days	Hospital-onset cases	Rate (hospital-onset cases per 100,000 bed-days)	Community-onset cases	Rate (community-onset cases per 100,000 population)
2017 to 2018	55,694,748	4,315	7.7	34,903,075	1,628	4.7	2,687	4.8
2018 to 2019	55,999,864	4,191	7.5	34,538,184	1,521	4.4	2,670	4.8
2019 to 2020	56,369,653	4,350	7.7	34,637,156	1,583	4.6	2,767	4.9
2020 to 2021	56,266,460	4,301	7.6	27,628,155	1,675	6.1	2,626	4.7
2021 to 2022	56,692,394	4,346	7.7	32,905,086	1,631	5.0	2,715	4.8
2022 to 2023	57,112,542	4,418	7.7	35,490,766	1,701	4.8	2,717	4.8
2023 to 2024	57,230,111	4,457	7.8	35,991,392	1,714	4.8	2,743	4.8
2024 to 2025	56,994,974	4,474	7.8	36,195,302	1,729	4.8	2,745	4.8

Note 1: financial year ranges from April of one year to March of the following year.

Note 2: ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Seasonal trends

Seasonality was assessed as the number of cases each quarter as a percentage of total cases for the financial year. This analysis was performed separately for hospital-onset and community-onset cases. When assessing the distribution of community-onset P. aeruginosa cases per financial year, the greatest proportion of cases occur in the July to September quarter of each financial year (Table S7 in the accompanying data). This has been observed since the beginning of P. aeruginosa surveillance in FY 2017 to 2018, where on average 28.4% of community-onset cases in the financial year occur in the summer quarter. Since FY 2017 to 2018 on average (except for FY 2020 to 2021) 27.2% of hospital-onset cases in the financial year occur in the summer quarter.

Prior trust exposure

There was an increase of 3.2% in the number of hospital-onset healthcare-associated (HOHA) P. aeruginosa cases in FY 2024 to 2025, compared to FY 2020 to 2021, rising from 1,675 to 1,729, with a 21.2% drop in the incidence rate of HOHA, from 6.1 to 4.8 cases per 100,000 bed-days. Over the same period, the number of community-onset healthcare-associated (COHA) cases increased by 3.7% from 753 to 781 cases, with a drop in the rate to 1.9 cases per 100,000 bed-days and day admissions in FY 2024 to 2025. Community-onset community-associated (COCA) cases increased by 6.6% from 1,842 to 1,964 and 5.3% from 3.3 to 3.4 cases per 100,000 population, respectively (Table S8 in the accompanying data).

Since FY 2020 to 2021 the distribution of cases by prior trust distribution has remained stable. In FY 2024 to 2025 43.9% of cases were COCA, 17.5% COHA and 38.6% HOHA (Figure 21).

These comparisons should be interpreted with caution as FY 2019 to 2020 had 430 cases without prior trust exposure data, which became mandatory in late 2019, and therefore may underestimate the proportion of COHA and COCA cases, compared with zero missing information cases in subsequent years.

Figure 21. Proportion of prior trust exposure of P. aeruginosa bacteraemia cases, England, by financial year, April 2020 to March 2025

Age and sex distribution

Overall, there was not much difference in the age and sex distribution of P. aeruginosa cases as a percentage of all reported cases in FY 2017 to 2018 and FY 2024 to 2025 (Figure 22 and Table S2 in the accompanying data). Most cases occurred in male cases aged 45 years and over. The highest proportion of cases for male and female cases in FY 2024 to 2025 occurred amongst those aged 75 to 84 years (also top in 45 to 64 year old females), accounting for 18.6% and 8.3% of total cases, respectively. Additionally, female cases were also notably high in those aged 45 to 64 years also accounting for 8.3%. Similar to Klebsiella spp., in FY 2024 to 2025, the percentage of male cases amongst those aged 15 to 44 years was like female cases. This was not the case for E. coli bacteraemia, for which female cases were substantially higher.

Figure 22. Age and sex distribution of P. aeruginosa bacteraemia by percentage of cases, England, by financial years April 2017 to March 2018 and April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, except for those aged one year and under, the incidence rate of P. aeruginosa bacteraemia increased with age for both male and female cases; the highest rate observed was amongst those aged 85 years and over. The rate in male cases aged 85 years and over between FY 2017 to 2018 to FY 2024 to 2025 increased by 2.8% (from 111.3 cases to 114.4 cases per 100,000 population). Over the same period, the rate in female cases aged 85 years and over decreased by 15.9% from 34.6 to 29.1 cases per 100,000 population (Figure 23), further widening the gap between the sexes.

Those aged one year and under are a relatively high-risk group. Of note, between FY 2017 to 2018 and FY 2024 to 2025, the rate for female cases in this age group increased, while male cases displayed a slight decrease. For female cases this increased by 38.6% from 6.7 to 9.3. For male cases, there was a 5.1% decrease from 9.7 to 9.2. All other age groups remained comparable between the 2 financial years.

Trends in the age-specific and sex-specific rates of P. aeruginosa bacteraemia are shown in Figure 23. The rates are higher in male cases compared with female cases, especially in the older age groups (aged 65 years and over). Since FY 2017 to 2018, the incidence rate in male cases aged 85 and older has fluctuated between 91.3 and 114.4 cases per 100,000 population. In FY 2024 to 2025, there was a rise in the incidence rate amongst male cases aged 85 years and over, a 5.2% increase (from 108.7 to 114.4 cases per 100,000 population) from the last financial year (FY 2023 to 2024). For male cases aged 75 to 84 years, there was an 8.2% decrease from 53.5 to 49.1, for the same period.

The rate of incidence for female cases aged 85 years and over was 29.1 for FY 2024 to 2025, a 12.2% increase since FY 2023 to 2024.

Generally, all other age groups, for both male and female cases, have remained broadly stable over the 7 years since the start of P. aeruginosa bacteraemia mandatory surveillance. The exception to this for both male and female cases was in those aged one year and under. Caution is advisable when interpreting data for P. aeruginosa amongst those aged 14 years and under as the number of cases is too small to properly interpret trends.

Cases in which the age and or sex was missing or reported as ‘unknown’ were excluded. In both FY 2017 to 2018 and FY 2024 to 2025, zero cases had an ‘unknown’ age or sex.

Figure 23. Trends in age group and sex rates of P. aeruginosa bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by ethnicity

In FY 2024 to 2025, the observed incidence rate of P. aeruginosa bacteraemia was highest in the Black and White ethnic groups (8.2 and 8.0 cases per 100,000 population, respectively) (Figure 24 and Table S14 in the accompanying data). It was intermediate in the Asian ethnic group (5.4 cases per 100,000 population), and lowest in the Mixed and Other ethnic groups (2.4 and 2.2 cases per 100,000 population, respectively).

Age-standardised incidence rates are much greater than observed incidence in all except the White ethnic group. The Black ethnic group sees the highest incidence compared with the other ethnic groups consistently over the surveillance period. However, recent years have seen a plateau at 13.0 cases per 100,000 population. The Asian ethnic group has seen an increasing trend since April 2017, while the White ethnic group has remained relatively constant at 7.3 cases per 100,000 population. The Other ethnic group has fluctuated in the past 8 years without trend.

Figure 24. P. aeruginosa bacteraemia rate by ethnicity, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by deprivation

Unlike the other reported organisms, in FY 2024 to 2025, the observed incidence rate for P. aeruginosa bacteraemia did not substantially differ by deprivation, ranging from 7.4 to 8.1 cases per 100,000 population (Figure 25 and Table S13 in the accompanying data).

However, age-sex standardised incidence rates of P. aeruginosa bacteraemia varied more widely by deprivation with larger or smaller rates than observed, with 9.6 and 6.5 cases per 100,000 population in the 20% most or 20% least deprived areas, respectively. Since April 2017, all levels have fluctuated without apparent trend.

Figure 25. P. aeruginosa bacteraemia rate by deprivation, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Primary focus of P. aeruginosa bacteraemia

Reporting of primary focus for P. aeruginosa remains low. In FY 2024 to 2025, the primary focus was reported for 46.9% of cases, a decrease from 49.3% from the start of surveillance in FY 2017 to 2018 (Table S4 in the accompanying data).

The most frequent primary focus of P. aeruginosa bacteraemia was the urinary tract, constituting 31.1% of cases in FY 2024 to 2025. Over the 8 financial years from April 2017 to March 2025, the percentage of primary focus reported as the urinary tract was similar (range: 28.8% to 31.1%) and was the most reported primary focus of bacteraemia (Table 9). As observed with Klebsiella spp., in the 3 financial years between April 2017 and March 2020 the percentage of cases reporting respiratory tract as a primary focus remained stable (range:13.0% to 14.1%). However, in FY 2020 to 2021, there was an increase in the percentage of primary focus reported as the respiratory tract to 16.1% which coincided with the first 2 waves of the COVID-19 pandemic. This reduced to 15.1% in FY 2021 to 2022 and then further declined to 12.4% by FY 2023 to 2024. In FY 2024 to 2025, the percentage increased to 13.5%, but this was in line with pre-pandemic levels.

Table 9. P. aeruginosa bacteraemia counts and percentages by primary focus of bacteraemia, England, by financial year: April 2017 to March 2025

Financial year [note 1]	Total P. aeruginosa reported	Primary focus ascertained: (number)	Primary focus ascertained: (%)	Gastro-intestinal: (number) [note 2]	Gastro-intestinal: (%) [note 2]	Hepatobiliary: (number)	Hepatobiliary: (%)	Urinary tract: (number)	Urinary tract: (%)	Respiratory tract: (number)	Respiratory tract: (%)	Other: (number) [note 3]	Other: (%) [note 3]	Unknown: (number)	Unknown: (%)
2017 to 2018	4,315	2,129	49.3%	126	5.9%	102	4.8%	638	30.0%	300	14.1%	491	23.1%	472	22.2%
2018 to 2019	4,191	2,161	51.6%	155	7.2%	100	4.6%	644	29.8%	281	13.0%	558	25.8%	423	19.6%
2019 to 2020	4,350	2,320	53.3%	160	6.9%	123	5.3%	716	30.9%	313	13.5%	549	23.7%	459	19.8%
2020 to 2021	4,301	2,118	49.2%	129	6.1%	116	5.5%	612	28.9%	341	16.1%	503	23.7%	417	19.7%
2021 to 2022	4,346	1,933	44.5%	117	6.1%	94	4.9%	600	31.0%	291	15.1%	461	23.8%	370	19.1%
2022 to 2023	4,418	1,915	43.3%	147	7.7%	96	5.0%	551	28.8%	268	14.0%	453	23.7%	400	20.9%
2023 to 2024	4,457	2,022	45.4%	148	7.3%	111	5.5%	593	29.3%	250	12.4%	503	24.9%	417	20.6%
2024 to 2025	4,474	2,099	46.9%	156	7.4%	118	5.6%	653	31.1%	284	13.5%	476	22.7%	412	19.6%

Note 1: financial year from April to March of the following year.

Note 2: gastrointestinal (not hepatobiliary).

Note 3: ‘Other’ includes the following options inputted on the HCAI DCS: bone and joint, central nervous system, genital tract (including prostate), indwelling intravascular device, other, respiratory tract, skin or soft tissue, no clinical signs of bacteraemia.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, for inpatients with a time-to-onset (days between hospital admission and specimen date) of fewer than 2 days, the most common primary focus of bacteraemia was the urinary tract (36.3%) (Table 10). As time between admission and positive specimen increased, the percentage of inpatients reporting primary focus as the urinary tract decreased to 22.5% amongst those with a time-to-onset of 7 days or greater.

In contrast, as the number of days between admission and positive specimen increased, so did the percentage of individuals with a reported respiratory tract primary focus from 10.3% amongst those with fewer than 2 days, peaking at 16.3% in the 2 to 6 days group before declining to 14.1% amongst those with 7 days or greater. Similarly, gastrointestinal (not hepatobiliary) increased from 6.6% amongst those with less than 2 days to 12.1% in the 2 to 6 days group followed by a decrease to 9.4% amongst those with 7 days or greater.

Table 10. Distribution of primary focus of P. aeruginosa bacteraemia, by time-to-onset, England, by financial year: April 2024 to March 2025

Time to onset (days) [note 1]	Gastrointestinal (not hepatobiliary) (number)	Gastrointestinal (not hepatobiliary) (%) [note 2]	Hepatobiliary (number)	Hepatobiliary (%) [note 2]	Urinary tract (number)	Urinary tract (%) [note 2]	Respiratory tract (number)	Respiratory tract (%) [note 2]	Other (number)	Other (%) [note 2]
Less than 2	41	6.6%	36	5.8%	225	36.3%	64	10.3%	119	19.2%
2 to 6	23	12.1%	21	11.1%	40	21.1%	31	16.3%	44	23.2%
7 and over	63	9.4%	43	6.4%	151	22.5%	95	14.1%	195	29.0%

Note 1: number of days from admission to positive bacteraemia sample (if both are on the same date the difference would be zero days).

Note 2: proportion of cases by primary focus.

Geographic distribution

The crude and age-sex standardised rates is presented across ICBs for FY 2024 to 2025. There was clustering of high incidence rates of P. aeruginosa in London while moderate rates are clustered across the country. Areas across the South West, North West and around Bristol typically had lower rates (Figure 26). The highest age-sex standardised incidence rate was observed in some London ICBs and Coventry and Warwickshire ICBs (14.2, 11.2, 11.0, 10.6 and 10.0 cases per 100,000 population), while the lowest were observed in Gloucestershire ICB (2.6 cases per 100,000 population), Devon ICB (4.4 cases per 100,000 population) and Lancashire and South Cumbria ICB (4.9 cases per 100,000 population) (Table S6 in the accompanying data).

Figure 26. Geographic distribution of P. aeruginosa bacteraemia rate, by Integrated Care Boards, England, by financial year: April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Mortality

In FY 2024 to 2025, 4,474 P. aeruginosa bacteraemia cases were reported in England (Table S9 in the accompanying data). Information on mortality was available for 98.9% (4,426) of these cases. There were 1,100 deaths within 30 days of a P. aeruginosa bacteraemia, with a mortality rate of 1.9 deaths per 100,000 population and a CFR of 24.7% (Figure 27).

The mortality rate has remained consistent at around 1.9 deaths per 100,000 population between FY 2021 to 2022 and FY 2024 to 2025. The CFR had decreased from 27.0% (1,161 deaths) in FY 2017 to 2018 to 24.7% (1,100 deaths) in FY 2024 to 2025.

Figure 27. Case-fatality rate and mortality rate of P. aeruginosa bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Variation by onset of bacteraemia

Between FY 2018 to 2019 and FY 2024 to 2025, the CFR of hospital-onset (HO) cases increased slightly from 27.2% to 28.0%, while for community-onset (CO) cases over the same period the CFR had minor fluctuations but declined marginally from 22.7% to 22.6% (Table S11 in the accompanying data). Compared with FY 2023 to 2024, CFR in HO cases in FY 2024 to 2025 decreased marginally from 28.4% to 28.0%, while CO cases increased slightly from 22.5% to 22.6%.

In FY 2024 to 2025, the mortality rate of HO cases remained stable at 1.3 deaths per 100,000 bed-days when compared the previous FY 2023 to 2024 (483 and 485 deaths, respectively). Over the same period, the mortality rate in CO cases remained stable at 1.1 deaths per 100,000 population (618 deaths and 616 deaths, respectively).

Variation by age and sex

In FY 2024 to 2025, CFR and mortality rate generally increased with age, except amongst children aged one year and under, which was higher than those aged one to 14 years (Table S10 in the accompanying data). The mortality rate was greater in male cases (except those aged 15 to 44 years) while the CFR was greater in female cases except those aged under one year.

In FY 2024 to 2025, the highest mortality rates in male cases were in those aged 85 years and over (31.8 deaths per 100,000 population) and those aged 75 to 84 years (12.0 deaths per 100,000 population), which corresponded to CFRs of 27.9% and 24.4% of cases, respectively.

In female cases of the same age groups, the mortality rates were far lower than their male counterparts; 10.0 deaths per 100,000 population (aged 85 years and over) and 6.5 deaths per 100,000 population (aged 75 to 84 years). However, these equated to higher CFRs than male cases of 34.4% and 35.4% of all cases in these age groups.

Amongst children aged one year and under, the mortality rate in male cases was 3.9 deaths per 100,000 population and 3.4 in female cases. As the number of deaths was relatively small in both male and female cases, caution is required in interpreting this data.

Variation by region

Case-fatality rates in FY 2024 to 2025 were highest in the North West (30.3%) followed by South East (26.1%) and the East of England (26.1%). The CFR remained lowest in London at 21.2% and South West (22.2%) (Table S12 in the accompanying data).

E. coli, Klebsiella spp. and P. aeruginosa discussion and comparison

Data reported on E. coli, Klebsiella spp. and P. aeruginosa continues to show both similarities and differences in the epidemiological trends of these bacteraemia.

E. coli continues to have the highest count and rate of all the Gram-negative organisms, with 43,639 cases and a rate of 76.6 cases per 100,000 population reported in FY 2024 to 2025; this is followed by Klebsiella spp. (n = 13,438, 23.6) and then P. aeruginosa cases (n = 4,474, 7.8).

Long-term trends of each bacteraemia show increasing incidence rates since the start of enhanced surveillance until at least the start of the COVID-19 pandemic. E. coli cases, which were previously showing a continued annual increase, declined considerably during FY 2020 to 2021. Since then, the incidence rate has been increasing, with the largest annual rise recorded since the inception of E. coli surveillance occurring between FY 2022 to 2023 to FY 2023 to 2024. By FY 2024 to 2025, the overall E. coli rate has almost reached pre-pandemic levels, raising particular concern with its continued upward trajectory.

This is also true for Klebsiella spp., and the increases are predominantly caused by community-onset cases. Further work and thorough investigations are underway to investigate (some details are available in the New and future work section of this report; however, more data is required to fully determine these changes in trend.

The observed decline of E. coli was not observed for Klebsiella spp. and P. aeruginosa bacteraemia. Further analysis conducted by the UK Health Security Agency (UKHSA) identified the increases corresponded with increases in hospital-onset cases that are a) secondary to COVID-19 cases, b) reported with respiratory tract as the primary focus of infection and c) reported in intensive care units (see the review of national surveillance data, August 2020 to February 2021 for further information). This suggests that the increases in hospital-onset cases are likely related to the COVID-19 pandemic. E. coli bacteraemia is less commonly associated with these factors compared to Klebsiella spp. and P. aeruginosa potentially explaining the difference in trend. It is important to note the rate for Klebsiella spp. remained high compared to pre-pandemic levels, however, the rate for P. aeruginosa returned to similar levels in line with earlier years of surveillance.

Amongst the Gram-negative bacteraemia cases with a known primary focus of infection, the urinary tract remains a major source of bacteraemia for all Gram-negatives, accounting for 46.3% of E. coli, 36.4% of Klebsiella spp. and 31.1% of P. aeruginosa. In FY 2020 to 2021, P. aeruginosa and Klebsiella spp. had their highest percentage of infections reported with a respiratory tract as primary focus with 16.1% and 12.9%, respectively. This peak in the respiratory tract as focus of infection coincided with the months of highest counts and rates of SARS-CoV-2 infection during the second COVID-19 wave in England, with further investigations revealing a proportion as being co-infected with COVID-19. This declined for both P. aeruginosa (13.5%) and Klebsiella spp. (9.1%) consecutively for the third financial year for FY 2024 to 2025, returning to reported pre-pandemic levels. Further information can be found in the review of national surveillance data, August 2020 to February 2021.

The age distribution of cases was similar in all 3 Gram-negative bacteraemias included in the mandatory surveillance programme. However, there were differences in the distribution of cases by sex. E. coli cases were more evenly distributed between male and female cases, while Klebsiella spp. and P. aeruginosa cases were more common in male cases, particularly in the older age groups.

Rates of each of the Gram-negative bacteraemia showed variations in geographic distributions in England with evidence of similar and relatively high infection rates amongst neighbouring ICBs for all 3 Gram-negative bacteraemia suggested by the observed data, although differences exist within the organism-specific patterns. More broadly, higher observed rates were generally found in each organism in the Northern and South East regions of England. However, following age-sex-standardisation, rates were generally highest in London and Northern regions. These regional differences across the organisms warrant further investigation.

Ethnicity and IMD data across all 3 Gram-negative bloodstream infections (GNBSIs) suggests those living in more deprived areas are disproportionately affected. After age-standardisation, Black and Asian ethnic groups had relatively higher incidence of GNBSIs compared to the White ethnic group. It should be noted that ethnicity and deprivation are linked, with those in some ethnic groups known to reside in more deprived areas. These findings highlight potential health inequalities, and a more detailed investigation is planned to investigate potential drivers to inform appropriate interventions (see the New and future work section of this report).

The National Action Plan (NAP) published in 2019 was the first in a series of action plans intended to achieve the 20-year vision for AMR. To inform future policy the Department of Health and Social Care (DHSC) commissioned an evaluation of the first NAP, which marked a significant step forward in addressing AMR, both in the UK and globally. Building on these successes, the new national action plan, ‘Confronting Antimicrobial Resistance 2024 to 2029,’ aims to make further progress towards this 20-year vision of containing, controlling, and mitigating AMR (antimicrobial resistance). As part of the 2024 to 2029 NAP, there is a target on GNBSIs incidence: By 2029, the aim is to prevent an increase in Gram-negative bloodstream infections in humans from the 2019 to 2020 financial year baseline.

Recently published research detailed the risk factors and predictors for mortality in these 3 organisms, by demographic, antimicrobial resistance, healthcare association and primary focus of infection:

Nsonwu O, Thelwall S, Gerver S, Guy RL, Chudasama D, Hope R. ‘Incidence, case-fatality rates and risk factors of bloodstream infections caused by Escherichia coli, Klebsiella species and Pseudomonas aeruginosa, England, April 2017 to March 2022’ (2025) Eurosurveillance.

Epidemiological analysis of Staphylococcus aureus bacteraemia

A total of 14,863 Staphylococcus aureus (S. aureus) bacteraemia cases were reported in FY 2024 to 2025, through both the meticillin-resistant S. aureus (MRSA) and meticillin-susceptible S. aureus (MSSA) bacteriaemia surveillance schemes. This represents a 3.0% increase in the numbers of bacteraemia caused by S. aureus from the previous FY (2023 to 2024, n = 14,401) and a 50.1% increase from the FY 2011 to 2012 (n=9,883) when case-level MSSA reporting was made mandatory.

In FY 2024 to 2025, 7.2% (n = 1,064) of S. aureus bacteraemia reports were caused by MRSA. This was a decrease from FY 2011 to 2012, in which 11.3% (n = 1,116) of reports were caused by MRSA. However, compared to the previous FY 2023 to 2024, in which only 6.3% (n = 910) of reports were caused by MRSA, it was an increase. At its peak, in FY 2007 to 2008, MRSA bacteraemia accounted for approximately 40% of all S. aureus bacteraemia cases in England.

MSSA accounted for 92.8% (n = 13,799) of all S. aureus bacteraemia reports in FY 2024 to 2025. Compared to the previous FY 2023 to 2024, this represents an increase of 2.3%. In contrast, compared to MRSA, this was an increase from FY 2011 to 2012 (start of MSSA surveillance), when 88.7% (n = 8,767) of reports attributed to MSSA.

Meticillin-resistant Staphylococcus aureus bacteraemia (MRSA)

Total reports

A total of 1,064 cases of MRSA bacteraemia were reported by NHS acute trusts in England in FY 2024 to 2025 (Table S1 in the accompanying data). This was a 16.9% increase from FY 2023 to 2024 (n = 910), and a 76.1% decrease from FY 2007 to 2008 (n = 4,451) when case-level MRSA surveillance began (Figure 29). The rate of incidence has declined from 8.6 cases per 100,000 population (FY 2007 to 2008) to 1.9 in FY 2024 to 2025. MRSA bacteraemia incidence rate plateaued between FY 2014 to 2015 and FY 2019 to 2020, ranging between 1.4 to 1.5 cases per 100,000 population, followed by a short decline to 1.2 during COVID-19 pandemic years (FYs 2020 to 2022). Between FY 2021 to 2022 and FY 2024 to 2025, the trend changed, with MRSA bacteraemia cases increasing by 56.8% to 1.9 cases per 100,000 population, the highest incidence rate since FY 2012 to 2013.

Figure 28. Trends in the all case and hospital-onset rate of MRSA bacteraemia, in England, by financial year: April 2007 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Hospital and community-onset reports

There were a total of 1,064 cases reported in FY 2024 to 2025, of which 367 (34.5%) were hospital-onset (HO) (1.0 cases per 100,000 bed-days) (Figure 28).

Comparing FY 2024 to 2025 with the previous year, there has been a 6.1% (346 to 367) increase seen in HO cases with no significant change in HO rate at 1.0. However, MRSA case rates have shown a substantial increase (43.2%) between FY 2021 to 2022 and FY 2024 to 2025, from 0.7 to 1.0. Historically, there has been a declining trend in the rate of hospital-onset MRSA from 4.3 in FY 2008 to 2009 (when this metric was first collected) to 0.7 in FY 2021 to 2022 (Table 11). The proportion of hospital-onset cases has also declined from 54.7% in FY 2008 to FY 2009 to the current 34.5% in FY 2024 to 2025.

For FY 2024 to 2025, there were 697 community-onset (CO) cases (1.2 cases per 100,000 bed-days). Monthly counts of MRSA bacteraemia since the start of surveillance highlights these recent increases in cases, particular of CO cases (Figure 29). CO cases have also displayed a sustained increase in case rates between FY 2020 to 2021 and FY 2024 to 2025, from 0.7 to 1.2 cases per 100,000 bed-days (65.0% increase). Similar to the HO rates, community-onset (CO) rates have previously shown a decline in rates from 2.6 to 0.7 cases per 100,000 population since initial surveillance in FY 2008 to 2009 to FY 2020 to 2021.

Table 11. MRSA bacteraemia counts and rates, England, by financial year: April 2007 to March 2025

In this table [x] is used when data is not collected for a metric.

Financial year [note 1]	Mid-year population estimate [note 2]	All reported cases	Rate (all reported cases per 100,000 population)	Total bed-days	Hospital-onset cases [note 3]	Rate (hospital-onset cases per 100,000 bed-days) [note 3]	Community-onset cases [note 3]	Rate (community-onset cases per 100,000 population) [note 3]
2007 to 2008	51,594,959	4,451	8.6	37,346,236	[x]	[x]	[x]	[x]
2008 to 2009	51,803,017	2,935	5.7	37,718,582	1,606	4.3	1,329	2.6
2009 to 2010	52,306,371	1,898	3.6	37,330,051	1,004	2.7	894	1.7
2010 to 2011	52,757,039	1,481	2.8	35,206,316	688	2.0	793	1.5
2011 to 2012	53,315,857	1,116	2.1	34,669,499	473	1.4	643	1.2
2012 to 2013	53,498,224	924	1.7	34,633,855	398	1.1	526	1.0
2013 to 2014	54,030,048	862	1.6	34,514,871	364	1.1	498	0.9
2014 to 2015	54,478,406	800	1.5	34,972,728	285	0.8	515	0.9
2015 to 2016	55,040,935	823	1.5	34,752,604	298	0.9	525	1.0
2016 to 2017	55,256,716	825	1.5	35,148,014	315	0.9	510	0.9
2017 to 2018	55,694,748	850	1.5	34,903,075	276	0.8	574	1.0
2018 to 2019	55,999,864	807	1.4	34,538,184	271	0.8	536	1.0
2019 to 2020	56,369,653	815	1.4	34,637,156	260	0.8	555	1.0
2020 to 2021	56,266,460	697	1.2	27,628,155	280	1.0	417	0.7
2021 to 2022	56,692,394	675	1.2	32,905,086	233	0.7	442	0.8
2022 to 2023	57,112,542	787	1.4	35,490,766	295	0.8	492	0.9
2023 to 2024	57,230,111	910	1.6	35,991,392	346	1.0	564	1.0
2024 to 2025	56,994,974	1,064	1.9	36,195,302	367	1.0	697	1.2

Note 1: financial year ranges from April of one year to March of the following year.

Note 2: ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Figure 29. Monthly counts of MRSA bacteraemia by onset of infection, England, by financial year: April 2007 to March 2025

Seasonal trends

There has been no discernible seasonal trend in either community-onset or hospital-onset MRSA cases since FY 2010 to 2011, as observed from the graph (Figure 29 and Table S7 in the accompanying data).

Prior trust exposure

In FY 2024 to 2025, there was a 41.2% increase (from 260 to 367) for the hospital-onset healthcare-associated (HOHA) cases compared to FY 2019 to 2020 (Table S8 in the accompanying data). There was also a slight increase in rate from 0.8 to 1.0 cases per 100,000 bed-days. In contrast, for the same period, the number of reported community-onset healthcare-associated (COHA) cases decreased by 8.5% (from 142 to 130), with a 12.2% decline in rate (from 0.4 to 0.3 cases per 100,000 bed-days and day admissions) from FY 2019 to 2020 to FY 2024 to 2025.

Community-onset community-associated (COCA) cases for FY 2024 to 2025 (n = 567) have exceeded FY 2019 to 2020 (n = 404) by 40.4%, for the first year since the start of prior trust exposure collection. With this increase, the COCA rate has also surpassed the FY 2019 to 2020 rate of 0.7 by 38.8% (1.0 in FY 2024 to 2025). The underlying numbers are relatively small so caution should be exercised when interpreting rates.

Since FY 2019 to 2020 the distribution of cases by prior trust distribution has seen fluctuations. In FY 2024 to 2025 there were 53.3% COCA cases, 12.2% COHA cases and 34.5% HOHA cases (Figure 30).

Caution is advised when comparing the prior trust exposure distribution for community-onset cases up to FY 2018 to 2019 within (Table S8 in the accompanying data). When these prior trust exposure fields were made mandatory the community-onset missing information fields saw a sharp decline which explains why Figure 30 displays data from FY 2019 to 2020 onwards.

Figure 30. Proportion of prior trust exposure of MRSA bacteraemia cases, England, by financial year, April 2019 to March 2025

Age and sex distribution

In FY 2007 to 2008, the greatest percentage of total cases amongst both male and female cases was in the 75 to 84 year age group (20.1% and 9.8%, respectively) (Figure 31 and Table S2 in the accompanying data). By FY 2024 to 2025, this had shifted with the highest proportion of male cases occurring amongst those aged 45 to 64 years (17.5%), whilst for female cases it was those aged 15 to 44 years (8.0%), though the distribution amongst female cases was more evenly distributed across adults (Figure 31). Across both years, male and female cases aged 14 years and under were consistently ranked as the lowest incidence rate out of all age groups. There was an increase in the percentage of cases contributed by this age group between FY 2007 to 2008 to FY 2024 to 2025. For children aged one year and under, the percentage increased from 0.7% (male cases) and 0.6% (female cases) to 1.7% (male) and 1.6% (female). Amongst those aged one to 14 years there was an increase from 0.5% (male cases) and 0.3% (female cases) to 2.6% (male) and 2.0% (female).

Figure 31. Age and sex distribution of MRSA bacteraemia by percentage of cases, England, by financial years: April 2007 to March 2008 and April 2024 to March 2025

At the start of MRSA surveillance (FY 2007 to 2008), higher MRSA rates were found in male cases in comparison to female cases, across all age groups. This remains the same for FY 2024 to 2025, with the greatest difference in rates observed in those aged 85 years and over, with a rate of 17.3 versus that of 6.6 in female cases. Both male and female cases observed increasing rates of infection with increasing age, with the exception amongst those aged one year and under, where rates were higher than the subsequent age groups until reaching those aged 75 years and over for male cases and 85 years and over for female cases.

Caution is advisable when interpreting data for MRSA amongst those aged 14 years and under as the number of cases is small to interpret trends well.

Since the start of MRSA surveillance, there have been large reductions in the number of bacteraemia reported. This decrease is reflected in the age-specific and sex-specific rates and trends of MRSA bacteraemia (Figure 32).

When comparing FY 2007 to 2008 and FY 2024 to 2025, the sharpest decline for both male and female cases is observed in those aged 75 to 84 years, from 73.9 (88.2% decline) to 8.7 in male cases and from 26.2 to 3.9 (85.1% decline) in female cases. Those aged 85 years and over also observed similar sharp declines for both male and female cases from 149.8 to 17.3 (88.5% decline) and from 44.2 to 6.6 (85.2% decline), respectively. The decline in younger age groups has been relatively moderate by comparison, with an increase in female cases in those aged one to 14 years, from 0.3 to 0.5 (48.5% increase). Male cases in the same group observed a rate increase from 0.5 to 0.6 per 100,000 population (12.0% increase). For all age and sex analyses, cases in which the age and/or sex was missing or recorded as unknown were excluded. In FY 2007 to 2008, 8 cases were reported with age or sex as unknown while in FY 2024 to 2025, no cases were reported with age or sex as unknown.

Figure 32. Trends in age group and sex rates of MRSA bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by ethnicity

In FY 2024 to 2025, the observed incidence rate of MRSA bacteraemia varied. Rates were highest in the Black and Asian ethnic groups (2.9 and 2.1 cases per 100,000 population, respectively) and lowest in Mixed ethnic group (0.4 cases per 100,000 population) (Figure 33 and Table S14 in the accompanying data).

When age-standardised, the highest rate in FY 2024 to 2025 was observed in the Black ethnic group (3.7), followed by the Asian ethnic group (3.6 cases per 100,000 population, respectively). Since FY 2021 to 2022 there has been a sharper rise in the Black and Asian ethnic groups compared to the others, with a doubling in the incidence rate over 3 years. Age-standardised rates for Mixed and Other ethnic groups could not be calculated for most of the period when their yearly counts were less than 10 for a given ethnic stratum. Therefore, the age-standardised rates for the Mixed and Other ethnic groups have high uncertainty and should be treated with caution.

Figure 33. MRSA bacteraemia rate by ethnicity, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs apart for the Other ethnic group where an error bar is used as its age-standardised rate could only be computed for a single year.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by deprivation

In FY 2024 to 2025, 2.5 cases per 100,000 people occurred in those living in the 20% most deprived areas versus 1.1 cases per 100,000 people living in the 20% least deprived areas (Figure 34 and Table S13 in the accompanying data).

Age-sex standardised incidence rates showed a much greater or lower incidence of MRSA bacteraemia than observed, with 2.9 and 1.0 cases per 100,000 population in the 20% most or 20% least deprived areas, respectively. Since FY 2022 the 2 most deprived quintiles have seen the greatest change in age-sex standardised incidence of MRSA bacteraemia, increasing more sharply compared with other quintiles.

Figure 34. MRSA bacteraemia rate by deprivation, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Source of MRSA bacteraemia

The Healthcare Associated Infections (HCAI) Data Capture System (DCS) provides NHS trust users the opportunity to add information regarding the likely source of bacteraemia. ‘Source of bacteraemia’ refers to the likely underlying cause of the bacteraemia, such as an intravenous catheter, or another infection at a different site, for example a skin and soft tissue infection which then led to bacteraemia. The provision of this information is voluntary and has declined over time in the MRSA surveillance. In FY 2007 to 2008, a total of 54.2% (n = 2,414) of MRSA records had entries (including ‘Unknown’) for the source of bacteraemia. By FY 2024 to 2025, only 27.6% (n = 294) MRSA records had entries for the source of bacteraemia (Table S14 in the accompanying data).

There was a decline in the percentage of MRSA cases in which the source of bacteraemia was a catheter or line between FY 2007 to 2008 and FY 2014 to 2015 period from 25.6% to 11.9%. However, between FY 2014 to 2015 period and FY 2024 to 2025, this had increased to 16.3%. In contrast, the proportion of cases caused by skin and soft tissue infections has steadily risen from 16.4% in FY 2007 to 2008 to 36.6% in FY 2023 to 2024. However, in FY 2024 to 2025, it decreased slightly to 32.3%.

Between FY 2007 to 2008 and FY 2014 to 2015, the percentage of cases for which the source of bacteraemia was pneumonia increased from 6.6% to 15.4%. This then plateaued until FY 2020 to 2021 (range: 13.1% to 15.4%). The percentage attributed to pneumonia subsequently saw a sharp decline in FY 2021 to 2022 to 6.3%. However, for FY 2024 to 2025, the percentage of cases have seen an increase to 14.6% (Table 12).

The underlying numbers are relatively small so caution should be exercised when interpreting these findings.

Table 12. MRSA bacteraemia counts and percentages by source of bacteraemia, England, by financial year: April 2007 to March 2025

Financial year [note 1]	Total MRSA	Source of bacteraemia reported: (number)	Source of bacteraemia reported: (%)	Catheters and lines (number) [note 2]	Catheters and lines (%) [note 2]	Skin and soft tissue (number)	Skin and soft tissue (%)	Pneumonia (number)	Pneumonia (%)	Other (number) [note 3]	Other (%) [note 3]	Unknown (number)	Unknown (%)
2007 to 2008	4,451	2,414	54.2%	617	25.6%	395	16.4%	160	6.6%	705	29.2%	537	22.2%
2008 to 2009	2,935	1,541	52.5%	346	22.5%	276	17.9%	113	7.3%	552	35.8%	254	16.5%
2009 to 2010	1,898	915	48.2%	178	19.5%	191	20.9%	63	6.9%	328	35.8%	155	16.9%
2010 to 2011	1,481	676	45.6%	118	17.5%	146	21.6%	47	7.0%	251	37.1%	114	16.9%
2011 to 2012	1,116	482	43.2%	71	14.7%	98	20.3%	41	8.5%	177	36.7%	95	19.7%
2012 to 2013	924	394	42.6%	72	18.3%	74	18.8%	34	8.6%	128	32.5%	86	21.8%
2013 to 2014	862	294	34.1%	39	13.3%	57	19.4%	33	11.2%	100	34.0%	65	22.1%
2014 to 2015	800	253	31.6%	30	11.9%	53	20.9%	39	15.4%	64	25.3%	67	26.5%
2015 to 2016	823	245	29.8%	38	15.5%	56	22.9%	25	10.2%	89	36.3%	37	15.1%
2016 to 2017	825	255	30.9%	51	20.0%	80	31.4%	21	8.2%	88	34.5%	15	5.9%
2017 to 2018	850	325	38.2%	50	15.4%	101	31.1%	40	12.3%	118	36.3%	16	4.9%
2018 to 2019	807	289	35.8%	37	12.8%	97	33.6%	30	10.4%	115	39.8%	10	3.5%
2019 to 2020	815	258	31.7%	33	12.8%	81	31.4%	24	9.3%	96	37.2%	24	9.3%
2020 to 2021	697	214	30.8%	34	15.9%	55	25.7%	28	13.1%	91	42.5%	6	2.8%
2021 to 2022	675	176	26.1%	31	17.6%	60	34.1%	11	6.3%	65	36.9%	9	5.1%
2022 to 2023	787	224	28.5%	37	16.5%	82	36.6%	16	7.2%	79	35.3%	10	4.5%
2023 to 2024	910	232	25.5%	41	17.7%	85	36.6%	22	9.5%	78	33.6%	6	2.6%
2024 to 2025	1,064	294	27.6%	48	16.3%	95	32.3%	43	14.6%	104	35.4%	4	1.4%

Note 1: financial year from April to March.

Note 2: catheters and lines include the following options from the HCAI DCS question: dialysis lines, central venous catheter (CVC) associated, peripheral venous catheter (PVC) associated and intravenous (IV) lines.

Note 3: ‘Other’ includes the following options HCAI DCS: endocarditis, osteomyelitis, other, prosthetic joint, surgical site infection (SSI), septic arthritis, urinary tract and ventilator-associated pneumonia.

Geographic distribution

The crude and age-sex standardised rates are presented across ICBs for FY 2024 to 2025 (Figure 35). The median age-sex standardised rate across ICBs is 1.8 MRSA bacteraemia cases per 100,000 population (Table S6 in the accompanying data). The highest age-sex standardised incidence rates were observed in Bristol, North Somerset and South Gloucestershire ICB (4.5 cases per 100,000 population), North-East London ICB (4.4 cases per 100,000 population) and North-West London ICB (3.0 cases per 100,000 population). While the lowest crude incidence rates (where age-sex-standardisation could not be computed) were observed in Cornwall and the Isles of Scilly ICB (0.3 cases per 100,000 population), South Yorkshire ICB (0.6 cases per 100,000 population) and Norfolk and Waveney ICB (0.8 cases per 100,000 population).

Figure 35. Geographic distribution of MRSA bacteraemia rate, by Integrated Care Boards, England, by financial year: April 2024 to March 2025

Note: ICBs which had 10 or fewer MRSA bacteraemia cases in financial year 2024 to 2025 are marked as a hashed area. Their crude rates are still available (Table S6 in the accompanying data). Although they had too few counts for standardisation this does not necessarily mean that their age-sex standardised rate would have been the lowest, only that they would be too imprecise to use.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Mortality

In FY 2024 to 2025, amongst the 1,064 MRSA bacteraemia cases reported in England, information on mortality was available for 98.3% (1,046 reports) (Table S9 in the accompanying data). Of those, there were 241 deaths within 30 days of an MRSA bacteraemia diagnosis, a mortality rate of 0.4 deaths per 100,000 population. There was an overall case-fatality rate (CFR) of 22.8% (Figure 36).

The CFR has been declining since the start of the surveillance (FY 2007 to 2008) compared to FY 2024 to 2025, from 38.9% to 22.8%. The overall trend of mortality rate decreased from 3.3 to 0.4 deaths per 100,000 population in the same period.

Figure 36. Case-fatality rate and mortality rate of MRSA bacteraemia, England, by financial year: April 2007 to March 2025

Note: shaded bands indicate 95% CIs.

Note: mid-year population estimates for January to December 2024 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.

Variation by onset of bacteraemia

The mortality rate of CO cases has remained consistent at 0.2 deaths per 100,000 population since FY 2018 to 2019 but has increased to 0.3 deaths per 100,000 in FY 2024 to 2025 (Table S11 in the accompanying data). In comparison, the mortality rate of HO cases decreased from 0.3 in FY 2023 to 2024 to 0.2 deaths per 100,000 bed-days (89 deaths) in FY 2024 to 2025.

In FY 2024 to 2025, the CFR decreased in HO cases from 28.4% to 24.2% and increased in CO cases from 20.4% to 22.0%, versus FY 2023 to 2024.

Variation by age and sex

In FY 2024 to 2025, except for those aged one year and under, mortality rate and CFR increased with age (Table S10 in the accompanying data). Over the same period, overall, the mortality rate was higher in male cases, but CFR was greater in female cases.

The highest mortality rate in male cases was in those aged 85 years and over (7.6 deaths per 100,000 population) and those aged 75 to 84 years (3.1 deaths per 100,000 population), with CFRs being 44.6% and 35.2%, respectively.

The mortality rate in female case was also higher in the oldest age groups, with a rate of 3.2 deaths per 100,000 population amongst those aged 85 years and over and 1.2 deaths per 100,000 population amongst those aged 75 to 84 years. The CFRs of these 2 groups were 48.3% and 31.2%, respectively.

There were relatively fewer deaths in cases aged one year and under compared with other age groups, however CFR in those aged one year and under remained slightly elevated for male cases at 12.5%. In FY 2024 to 2025, there were zero deaths within 30 days in both male and female cases aged one to 14 years. Additionally, female cases aged one year and under also reported zero deaths within 30 days.

Variation by region

The CFR in FY 2024 to 2025 were highest in the South East (27.7%), followed by the North West (25.4%) and East of England (24.5%). The CFR remained lowest in the South West at 16.9% and London (17.6%) (Table S12 in the accompanying data).

MRSA overview of trends

MRSA bacteraemia rates declined consistently each year between FY 2007 to 2008 and FY 2014 to 2015. In FY 2015 to 2016, the rate increased slightly but remained relatively stable until FY 2020 to 2021, when there was a considerable decline in the rate of all reported cases compared to the previous years. Counts and rates for the past 4 years, however, have shifted to an increasing trend. For the first time counts and rates have exceeded FY 2012 to FY 2013 levels at 1.9 cases per 100,000 in FY 2024 to 2025. Community-onset incidence rate has also exceeded FY 2012 to 2013 levels at 1.2 cases per 100,000 in FY 2024 to 2025. Whilst an increase in hospital-onset cases was observed between FY 2022 to FY 2023 and FY 2024 to 2025, with the rate increasing from 0.8 to 1.0 cases per 100,000 bed-days.

Numerous interventions aimed at reducing the incidence of MRSA bacteraemia and other infections have been introduced from the beginning of the surveillance programme for MRSA, contributing to the large reductions seen.

These include:

‘Winning Ways’ policy document published by the Department of Health (DoH) in 2003
‘Clean Your Hands’ campaign launched by the National Patient Safety Agency in 2014
‘Saving Lives’ programme launched by the DoH in 2005 which included the ambition to halve MRSA rates by 2008
2006 Health Act which introduced a code of practice to provide guidance on reducing HCAI including MRSA
Health and Social Care Act, 2008 which requires the code of practice to be regularly updated

The epidemiology of MRSA has changed since its peak in FY 2007 to 2008, and since FY 2010 to 2011 community-onset cases have been the most common. This switch in setting is most likely due to most MRSA bacteraemia interventions being concentrated in the acute care setting, and therefore the largest reductions in MRSA bacteraemia were seen in hospital-onset cases. The duration of stay of hospital patients is also on the decline. In 2001 the average length of stay for a hospitalised patient was 7.4 days in the UK, this decreased to 6.2 days in 2019. Comparing 2019 and 2022, the average length of stay for admissions increased by around 0.1 days (1.3%) (The Health Foundation). Shorter hospital stays lessen the risk of acquiring a hospital-acquired infection (HAI).

The percentage of MRSA bacteraemia where the likely source of infection was a catheter or a line has shown steady decrease since the early years of surveillance. However, between FY 2019 to 2020 and FY 2021 to 2022, the percentage increased from 12.8% to 17.6%. In FY 2024 to 2025, the percentage decreased to 16.3% in line with earlier years of surveillance. Despite some fluctuations in recent years, an overall decline is observed from the start of the surveillance period.

The initial declines in the percentage of MRSA bacteraemia where the most likely source of infection is a catheter or line have been noted previously. This may have been due to greater clinical awareness of the importance of this route of infection; the introduction of care bundles aimed at reducing infections in intravascular lines; or selective decolonisation of patients with MRSA carriage. After the increase observed in the last financial year, the decline in the current year may be an indicator of recovery from the pandemic but will require further investigation to determine the exact cause. Please note that the numbers that make up this period are relatively small compared to those observed at the MRSA peak.

The percentage where the source of bacteraemia is something other than catheters or intravenous lines have fluctuated considerably over time. The percentage of infections whose likely source is skin, or soft tissue infection appears to have increased over time (from 16.4% in FY 2007 to 2008 to 32.3% in FY 2024 to 2025). However, during FY 2024 to 2025 only a quarter (27.6%) of records had information on the likely source of bacteraemia and therefore interpretation of this data should be approached with caution.

Cases are more prevalent in the most deprived areas of England, and in mostly Black and Asian ethnic groups, highlighting potential health inequalities. There was also a steep rise in the Black ethnic group in the most recent financial year.

The marginal increase in the rate of hospital-onset cases and the decrease in percentage of infections due to catheters and lines since FY 2014 to 2015 may point to a need to continue concentration on NHS trust-based infection prevention initiatives to reduce hospital-onset cases further. In addition to maintaining good practice in an acute trust setting, interventions are required in the community setting, considering most MRSA cases are community-onset.

Meticillin-susceptible Staphylococcus aureus (MSSA) bacteraemia

Total reports

A total of 13,799 cases of MSSA bacteraemia were reported by NHS acute trusts in England in FY 2024 to 2025, an increase of 2.3% compared to FY 2023 to 2024 (n = 13,491), and an increase of 57.4% versus FY 2011 to 2012 (n = 8,767) (Figure 38) when mandatory reporting for MSSA BSI began (Table S1 in the accompanying data).

The rate of all MSSA cases per 100,000 population, per year has risen from 16.4 during FY 2011 to 2012 to 24.2 in FY 2024 to 2025. When compared to the pre-pandemic FY 2018 to 2019 (21.6) a 12.0% increase was observed.

Figure 37. Trends in the rate of MSSA bacteraemia, England, by financial year: April 2011 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Hospital and community-onset reports

Between FY 2011 to 2012 and FY 2018 to 2019, the hospital-onset (HO) incidence rate steadily increased from 8.2 cases to 9.6 per 100,000 bed-days, an increase of 17.2% (Figure 37 and Table 13). In FY 2020 to 2021, the HO incidence rate increased sharply to 12.1 (n = 3,344 of 11,717), a one-year increase of 26.5%. Hospital activity was reduced in FY 2020 to 2021 compared to other years. The HO rate subsequently declined in FY 2024 to 2025, to 11.0 cases per 100,000 bed-days (n = 3,966 of 13,799). Although the rate declined, it is still higher than pre-pandemic levels.

Community-onset (CO) cases similarly increased year-on-year, with cases and incidence rate increasing from 5,913 and 11.1 cases per 100,000 population, respectively, in FY 2011 to 2012 to 8,774 and 15.7 cases per 100,000 population in FY 2018 to 2019. There was a subsequent decline at the start of the COVID-19 pandemic, when cases and incidence rates dropped to 8,373 and 14.9 in FY 2020 to 2021, the only year recording a decline in trend. The rate has since reached 17.3 in FY 2024 to 2025, the highest since the start of surveillance, with year-on-year increases in the intervening years. The recent increases, particular those of community-onset, can be seen at a monthly level by onset status in Figure 38.

Table 13. MSSA bacteraemia counts and rates, England, by financial year: April 2011 to March 2025

Financial year [note 1]	Mid-year population estimate [note 2]	All reported cases	Rate (all reported cases per 100,000 population)	Total bed-days	Hospital-onset cases	Rate (hospital-onset cases per 100,000 bed-days)	Community-onset cases	Rate (community-onset cases per 100,000 population)
2011 to 2012	53,315,857	8,767	16.4	34,669,499	2,854	8.2	5,913	11.1
2012 to 2013	53,498,224	8,812	16.5	34,633,855	2,700	7.8	6,112	11.4
2013 to 2014	54,030,048	9,290	17.2	34,514,871	2,696	7.8	6,594	12.2
2014 to 2015	54,478,406	9,865	18.1	34,972,728	2,809	8.0	7,056	13.0
2015 to 2016	55,040,935	10,610	19.3	34,752,604	2,921	8.4	7,689	14.0
2016 to 2017	55,256,716	11,501	20.8	35,148,014	3,098	8.8	8,403	15.2
2017 to 2018	55,694,748	11,959	21.5	34,903,075	3,156	9.0	8,803	15.8
2018 to 2019	55,999,864	12,106	21.6	34,538,184	3,332	9.6	8,774	15.7
2019 to 2020	56,369,653	12,252	21.7	34,637,156	3,315	9.6	8,937	15.9
2020 to 2021	56,266,460	11,717	20.8	27,628,155	3,344	12.1	8,373	14.9
2021 to 2022	56,692,394	12,312	21.7	32,905,086	3,716	11.3	8,596	15.2
2022 to 2023	57,112,542	13,139	23.0	35,490,766	3,908	11.0	9,231	16.2
2023 to 2024	57,230,111	13,491	23.6	35,991,392	3,885	10.8	9,606	16.8
2024 to 2025	56,994,974	13,799	24.2	36,195,302	3,966	11.0	9,833	17.3

Note 1: financial year ranges from April of one year to March of the following year.

Note 2: ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Figure 38. Monthly counts of MSSA bacteraemia by onset of infection, England, by financial year: April 2011 to March 2025

Seasonal trends

There has been no discernible seasonal trend in either community-onset or hospital-onset MSSA cases since FY 2011 to 2012, as observed from the graph (Figure 38 and Table S7 in the accompanying data).

Prior trust exposure

In comparison to FY 2023 to 2024, FY 2024 to 2025 observed a small (2.1%) increase in the count of hospital-onset healthcare-associated (HOHA) MSSA bacteraemia from 3,885 to 3,966, with a corresponding increase in the rate of HOHA incidence from 10.8 to 11.0 cases per 100,000 bed-days (Table S8 in the accompanying data). Community-onset healthcare-associated (COHA) cases in FY 2023 to 2024 have remained the same as the previous year (n = 1,723), with the rate at 4.3 cases per 100,000 bed-days and day admissions.

Since FY 2023 to 2024, community-onset community-associated (COCA) increased from 7,849 to 8,092 (3.1%) which corresponded to a 3.5% increase in the COCA rate from 13.7 to 14.2 cases per 100,000 population.

Since FY 2019 to 2020 the distribution of cases by prior trust distribution has remained relatively stable. In FY 2024 to 2025, 58.6% of cases were COCA, 12.5% COHA and 28.7% HOHA (Figure 39).

Caution is advised when comparing the prior trust exposure distribution for community-onset cases up to FY 2018 to 2019 within (Table S8 of the accompanying data). When these prior trust exposure fields were made mandatory the community-onset missing information fields saw a sharp decline which explains why Figure 30 displays data from FY 2019 to 2020 onwards.

Figure 39. Proportion of prior trust exposure of MSSA bacteraemia cases, England, by financial year, April 2019 to March 2025

Age and sex distribution

Unlike that seen for MRSA, broadly the distribution of cases by age and sex for MSSA bacteraemia has remained similar despite general increasing numbers of MSSA cases and associated incidence rates (Figure 37, Figure 40, and Table S2 of the accompanying data).

In FY 2024 to 2025, the bulk of the total cases was in adults aged 45 years and over with more male cases (1.9 times more than female cases). Male cases had an increased MSSA incidence rate in all age groups versus female cases. Compared to FY 2011 to 2012, the proportion of cases in those aged one year and under versus all age groups in FY 2024 to 2025 was observed to decline for both male and female cases, from 3.0% to 1.5% in male cases and from 2.2% to 1.1% in female cases.

Figure 40. Age and sex distribution of MSSA bacteraemia by percentage, England, by financial years: April 2011 to March 2012 and April 2024 to March 2025

Between FY 2011 to 2012 and FY 2024 to 2025, the highest rates of MSSA incidence in male cases were observed amongst individuals aged 75 to 84 years and aged 85 years and over versus other age groups, increasing by 42.3% from 77.3 to 110.0 per 100,000 population and 66.0% from 137.6 to 228.4, respectively (Figure 41).

Similarly to male cases, the highest incidence rates in female cases in FY 2011 to 2012 and FY 2024 to 2025 were observed amongst those aged 75 to 84 years and aged 85 years and over versus other age groups, increasing by 32.1% from 39.7 to 52.4 cases per 100,000 population and by 36.1% from 67.1 to 91.4 cases per 100,000 population, respectively.

Those aged one year and under also have relatively high rates in comparison to the rates in some of those aged 65 years and under, with a male rate of 69.3 cases per 100,000 and female rate of 51.9 cases per 100,000. For all age and sex analyses, cases in which the age or sex was missing or recorded as unknown were excluded. In the first financial year of MSSA mandatory surveillance (FY 2011 to 2012), 16 (0.2%) gave the age or sex as ‘unknown’ versus zero cases in FY 2024 to 2025.

Figure 41. Trends in age group and sex rates of MSSA bacteraemia, England, by financial year: April 2011 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by ethnicity

In FY 2024 to 2025, the observed incidence rate of MSSA bacteraemia was highest in the White ethnic group (25.4 cases per 100,000 population), followed by the Black and Asian ethnic groups (18.0 and 14.2 cases per 100,000 population, respectively) and lowest in the Mixed and Other ethnic groups (8.5 and 4.9 cases per 100,000 population, respectively) (Figure 42 and Table S14 in the accompanying data).

When rates were age-standardised Black, White and Asian ethnic groups were ranked highest with rates of 25.0, 23.6 and 22.1 cases per 100,000 population, respectively. In FY 2020 to 2021 there was an increase in age-standardised incidence rate in the Asian and Black ethnic groups, contrary with a decrease in all other ethnic groups.

Figure 42. MSSA bacteraemia rate by ethnicity, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by deprivation

In FY 2024 to 2025, 29.9 cases per 100,000 people occurred in those living in the 20% most deprived areas versus 19.1 cases per 100,000 people living in the 20% least deprived areas (Figure 43 and Table S13 in the accompanying data). The observed incidence rate of MSSA bacteraemia generally increased with deprivation. The general trend since FY 2020 is an increase in incidence across all IMD quintiles, except for a recent plateau in the 40% to 60% most deprived level.

Age-sex standardised incidence rates in FY 2024 to 2025 are greater or smaller than the observed at 36.2 and 16.5 cases per 100,000 population in the 20% most or 20% least deprived areas, respectively. Yet the same trends in the observed incidence rate are mirrored in age-sex standardised incidence, with increased deprivation seeing increased incidence. These differences in age-sex standardised incidence rate of MSSA bacteraemia has been consistently ordered by deprivation since April 2018.

Figure 43. MSSA bacteraemia rate by deprivation, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Source of MSSA bacteraemia

The number of records reporting a source of bacteraemia has been steadily declining since the start of MSSA mandatory surveillance. In FY 2011 to 2012, a total of 3,305 (37.7%) records had entries for the source of bacteraemia (Table S4 in the accompanying data). By FY 2024 to 2025, a total of 3,867 (28.0%) had entries for the source of bacteraemia due to a lack of reporting.

The percentage of cases caused by skin and soft tissue infections has increased from 20.3% in FY 2011 to 2012 to 27.7% in FY 2024 to 2025. Similarly, the percentage of cases caused by pneumonia has also risen substantially from 6.0% in FY 2011 to 2012 to 12.6% in FY 2024 to 2025. The percentage of MSSA cases with catheter or line as the reported source of infection fluctuated between 13.1% and 15.7% during FY 2013 to 2014 and FY 2019 to 2020. However, since FY 2019 to 2020 the percentage of MSSA cases with catheter or line as the reported source of infection has fluctuated around 16.3% to 17.7%.

Although the percentage of records for which the source of infection was not reported has increased, the percentage of cases for which the source of infection was reported as ‘unknown’ has decreased from 23.6% to 3.2% during FY 2011 to 2012 to FY 2024 to 2025 (Table 14).

Table 14. MSSA bacteraemia counts and percentages by source of bacteraemia, England, by financial year: April 2011 to March 2025

Financial year [note 1]	Total MSSA	Source of bacteraemia reported (number)	Source of bacteraemia reported: (%)	Catheters and lines (number) [note 2]	Catheters and lines (%) [note 2]	Skin and soft tissue (number)	Skin and soft tissue (%)	Pneumonia (number)	Pneumonia (%)	Other (number) [note 3]	Other (%) [note 3]	Unknown (number)	Unknown (%)
2011 to 2012	8,767	3,305	37.7%	565	17.1%	670	20.3%	197	6.0%	1,093	33.1%	780	23.6%
2012 to 2013	8,812	3,266	37.1%	492	15.1%	699	21.4%	232	7.1%	1,088	33.3%	755	23.1%
2013 to 2014	9,290	3,236	34.8%	435	13.4%	684	21.1%	218	6.7%	1,124	34.7%	775	23.9%
2014 to 2015	9,865	3,398	34.4%	445	13.1%	706	20.8%	305	9.0%	1,087	32.0%	855	25.2%
2015 to 2016	10,610	3,225	30.4%	493	15.3%	769	23.8%	306	9.5%	1,170	36.3%	487	15.1%
2016 to 2017	11,501	3,185	27.7%	501	15.7%	871	27.3%	365	11.5%	1,279	40.2%	169	5.3%
2017 to 2018	11,959	3,530	29.5%	516	14.6%	1,003	28.4%	446	12.6%	1,440	40.8%	125	3.5%
2018 to 2019	12,106	3,732	30.8%	579	15.5%	1,030	27.6%	450	12.1%	1,595	42.7%	78	2.1%
2019 to 2020	12,252	4,152	33.9%	633	15.2%	1,175	28.3%	503	12.1%	1,729	41.6%	112	2.7%
2020 to 2021	11,717	3,568	30.5%	580	16.3%	969	27.2%	447	12.5%	1,498	42.0%	74	2.1%
2021 to 2022	12,312	3,402	27.6%	600	17.6%	968	28.5%	352	10.3%	1,392	40.9%	90	2.6%
2022 to 2023	13,139	3,365	25.6%	547	16.3%	976	29.0%	407	12.1%	1,321	39.3%	114	3.4%
2023 to 2024	13,491	3,776	28.0%	657	17.4%	1,117	29.6%	455	12.0%	1,417	37.5%	130	3.4%
2024 to 2025	13,799	3,867	28.0%	684	17.7%	1,073	27.7%	489	12.6%	1,496	38.7%	125	3.2%

Note 1: financial year from April to March.

Note 2: catheters and lines include the following options from the HCAI DCS question: dialysis lines, central venous catheter (CVC) associated, peripheral venous catheter (PVC) associated and intravenous (IV) lines.

Note 3: ‘Other’ includes the following options HCAI DCS: endocarditis, osteomyelitis, other, prosthetic joint, surgical site infection (SSI), septic arthritis, urinary tract and ventilator-associated pneumonia.

Geographic distribution

The crude and age-sex standardised rates is presented across ICBs for FY 2024 to 2025 in Figure 44. The ICBs with the highest age-sex standardised rates were North East and North Cumbria ICB (31.4 cases per 100,000 population), Cheshire and Merseyside ICB (30.7 cases per 100,000 population) and South Yorkshire ICB (30.3 cases per 100,000 population) (Table S6 in the accompanying data). The ICBs with the lowest age-sex standardised rates were Gloucestershire ICB (14.7 cases per 100,000 population), Leicester, Leicestershire and Rutland ICB (16.1 cases per 100,000 population) and Hertfordshire and West Essex ICB (17.9 cases per 100,000 population). Clustering of high MSSA incidence rate covers more ICBs in contrast to MRSA where high-low incidence neighbouring ICBs are more common (Figure 44 and Figure 35).

Figure 44. Geographic distribution of MSSA bacteraemia rate, by Integrated Care Boards, England, by financial year: April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Mortality

In FY 2024 to 2025, of the 13,799 MSSA bacteraemia cases reported in England, information on mortality was available for 99.0% (13,658) (Table S9 in the accompanying data). There were 2,919 deaths within 30 days of an MSSA bacteraemia diagnosis, with mortality rate of 5.1 deaths per 100,000 population and case-fatality rate (CFR) of 21.2% (Figure 45). Between FY 2023 to 2024 and FY 2024 to 2025, the trend in CFR increased from 20.2% to 21.2%. Over the same period, the overall trend of mortality rate also increased from 4.7 to 5.1 deaths per 100,000 population, reaching the highest point since the start of surveillance. MSSA is the only organism in this report where both mortality rates and case-fatality rates have increased on the previous year.

Figure 45. Case-fatality rate and mortality rate of MSSA bacteraemia, England, by financial year: April 2011 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Variation by onset of bacteraemia

The mortality rate of CO cases increased from 3.1 to 3.4 deaths per 100,000 population (1,762 to 1,958 deaths) between FY 2023 to 2024 and FY 2024 to 2025 (Table S11 in the accompanying data). Similarly, the mortality rate of HO cases increased from 2.6 to 2.7 deaths per 100,000 bed-days (952 to 961 deaths) for the same period.

Compared to the previous year, in FY 2024 to 2025, the CFR of CO cases increased from 18.4% to 20.0%. For HO cases the CFR decreased from 24.5% to 24.3%.

Variation by age and sex

In FY 2024 to 2025, the mortality rate and CFR increased with age except for the under one year olds (Table S10 in the accompanying data). The mortality rate was generally greater in male cases while CFR was similar in both male and female cases.

The highest mortality rates in male cases were in those aged 85 years and over (97.6 deaths per 100,000 population), followed by those aged 75 to 84 years (33.1 deaths per 100,000 population) with higher CFRs in these age groups compared to overall, at 42.8% and 30.1%, respectively.

In female cases, the mortality rates were also higher in older age groups, 41.6 deaths per 100,000 population (aged 85 years and over) and 15.7 deaths per 100,000 population (aged 75 to 84 years). These result in a CFR of 45.6% and 30.0% of all cases in those respective age groups.

Amongst children aged one year and under, the mortality rate in male cases was 1.6 deaths per 100,000 population compared with 2.1 deaths per 100,000 population in female cases.

The numbers of deaths in the one year and under group are small so caution should be exercised in interpretation.

Variation by region

Case-fatality rates in FY 2024 to 2025 were highest in the Midlands (23.2%) followed by the South West (22.3%) and the North East and Yorkshire (22.3%). The CFR remained lowest in London at 16.1% and the South East (20.2%) (Table S12 in the accompanying data).

MSSA overview of trends

The mandatory surveillance of MSSA bacteraemia was introduced in January 2011. The total number of MSSA bacteraemia has been steadily increasing throughout the 14-year surveillance period, although this trend has 2 components. Firstly, from FY 2011 and 2012 to FY 2016 and 2017 community-onset bacteraemia increased from 5,913 to 8,403 (a 42.1% increase). The second component relates to hospital-onset infections during the time between FY 2017 and 2018 to FY 2024 and 2025. During this time, the number of community-onset infections remained relatively stable while hospital-onset infections increased from 3,156 to 3,966 (a 25.7% increase).

In the first 2 financial years of surveillance (between FY 2011 to 2012 and FY 2012 to 2013), the case rates for MSSA bacteraemia were stable, before increasing each subsequent financial year until FY 2020 to 2021, when the rate fell from 21.7 cases per 100,000 population to 20.8.

For FY 2024 to 2025, the rate has increased to 24.2, signifying a return to the trend seen in earlier years of surveillance. Hospital-onset rates have mostly increased annually; with a sharp rise observed between FY 2019 to 2020 and FY 2020 to 2021 from 9.6 to 12.1, respectively. Compared to FY 2020 to 2021, hospital-onset rates have seen a small reduction from 12.1 to 11.0 in FY 2024 to 2025. With the rise in incidence, all-cause mortality rates are also seen to be rising when compared to the pre-pandemic financial years.

Age and sex structure of MSSA bacteraemia has changed little over the time since surveillance began. The trend shows that the number and rate of infections have increased more in older age groups, particularly amongst male cases, with the highest rate seen in male cases aged 85 years and over. The highest all-cause mortality rates are also seen in the older aged population, particularly those aged 85 years and over, and has been rising annually. Furthermore, male cases also generally show higher rates of MSSA bacteraemia compared to female cases. However, rates of MSSA bacteraemia are also higher in the youngest age group (aged one year and under), compared to young cases (aged one to 14 years old) and adults (aged 15 to 74 years) but still lower than in the oldest age groups (aged 75 to 84 years and over 85).

Despite the increase in MSSA bacteraemia rates over the years, little change has been observed in the rate ratios between male and female cases.

Enhanced surveillance and epidemiological studies in neonatal units and young infants have shown that MSSA cases in very young infants - especially preterm or those requiring invasive support - are predominantly healthcare‑associated and frequently linked to intravascular devices. For example, a paediatric S. aureus bacteraemia surveillance study in the Journal of Hospital Infection, reported that 33.8% of MSSA cases in neonates had vascular access device entry points and cases under 28 days old were strongly associated with healthcare acquisition. Additional neonatal intensive care unit (NICU) surveillance studies corroborate these findings, showing that extremely premature infants and those with invasive ventilation are at substantially higher risk of MSSA infection within hospital settings (National Library of Medicine ).

Like Gram-negative and MRSA bacteraemia, those living in the most deprived areas have a disproportionately higher incidence rate. The age-standardised ethnicity data shows the Black ethnic group to have the highest incidence, followed by White and Asian ethnic groups.

In FY 2024 to 2025, there appears to be no similarities between the geographical distribution of MRSA and MSSA. MSSA appears to be most prevalent in the northern regions of England, while rates of MRSA bacteraemia are more evenly distributed across north and south regions of the country.

As we see rates of MRSA and MSSA bacteraemia increasing we will also see associated rises in the 30-day all-cause mortality rate which is amplified in MSSA where CFR is also increasing. More focus is required on understanding what is causing this increase and what can be done to stop it.

Laboratory blood cultures

On a quarterly basis NHS acute trusts are mandated to report the total number of blood culture sets examined. Below is a summary of these aggregated blood culture set results through the years for Gram-negative bacteraemia, MSSA and MRSA.

The rate of blood culture sets examined gradually increased between FY 2010 to 2011 and FY 2019 to 2020, rising from 30.7 to 36.7 per 1,000 population (Figure 46 and Table S15 in the accompanying data). There was a subsequent decrease in FY 2020 to 2021 where the rate declined to 31.6 per 1,000 population, coinciding with the start of major COVID-19 restrictions and national lockdowns. The rate has since reverted to an upward trajectory, surpassing pre-pandemic levels and increasing to 39.2 per 1,000 population in FY 2024 to 2025.

Figure 46. Trends in the rate of blood culture sets, England, by financial year: April 2010 to March 2025

Note: shaded bands indicate 95% CIs.

The proportion of positive blood cultures for organisms under mandatory reporting (E. coli, Klebsiella spp., P. aeruginosa, MRSA and MSSA) has remained relatively stable with minor fluctuation since the start of surveillance, including a slight increase during FY 2020 to 2021 (Figure 47 and Table S16 in the accompanying data). The current proportion of positive tests in FY 2024 to 2025 is 3.4% which is the same as the previous year. While the sampling rate has increased concurrently with the overall increase in bacteraemia incidence rates, this does not appear to have impacted positivity, which has remained relatively stable (between 3.3 to 3.6% during the surveillance period). However, there may be variation by data collection or at trust-level.

Figure 47. Trends in pooled E. coli, Klebsiella spp., P. aeruginosa, MRSA and MSSA blood culture positivity, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

Epidemiological analysis of Clostridioides difficile infection (CDI)

Total reports

CDI surveillance collects data for those aged 2 years and over only. A total of 18,970 cases of CDI were reported by NHS acute trusts in England FY 2024 to 2025 (Figure 49 and Table S1 in the accompanying data). This was an increase of 12.7% from the previous financial year (FY 2023 to 2024, n = 16,838). The prevalence of CDI in England for all reported cases can be broken down into 3 distinct periods: the first between FY 2007 to 2008 and FY 2013 to 2014 is characterised by a rapid decline in the incidence rate from 107.6 to 24.7 cases per 100,000 population, representing a 77.0% reduction; the second is one of continued but more gradual decline and relative stability in the incidence rate, with minimal fluctuation between FY 2013 to 2014 (24.7 cases per 100,000 population) until FY 2020 to 2021; the final period, starting in FY 2021 to 2022 sees a shift to a sustained increasing trend for the first time since the inception of the surveillance programme in 2007, with a significant increase in cases annually, with rates reaching 33.3 infections per 100,000 population in FY 2024 to 2025, a 13.1% annual increase from the rate seen in the previous year.

While incidence of CDI has increased in recent years, the overall rate in FY 2024 to 2025 remains substantially lower (69.1%) than the start of surveillance in FY 2007 to 2008 (Figure 48).

Figure 48. Trends in the rate of CDI, England, by financial year: April 2007 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Hospital and community-onset reports

A total of 18,970 cases reported in FY 2024 to 2025, of which 8,430 cases were hospital-onset (23.3 cases per 100,000 bed-days) (Figure 48 and Table 15. There was a decline of 82.4% in hospital-onset (HO) incidence rates from the start of surveillance in FY 2007 to 2008 (94.5 cases per 100,000 bed-days) to FY 2013 to 2014 (16.6 cases per 100,000 bed-days). The decrease in trend with some fluctuations continued between FY 2013 to 2014 and FY 2018 to 2019 with the rate dropping from 16.6 to 14.1 (15.3% decrease). Following this, the rate of hospital-onset CDI cases has increased each year from 14.1 to 23.3 cases per 100,000 bed-days by FY 2024 to 2025, a 65.2% increase.

The community-onset (CO) rate followed a similar trend, with a 64.0% decline from the start of surveillance to FY 2013 to 2014 (39.2 to 14.1 cases per 100,000 population, respectively). After some fluctuations, the rate dropped to 13.5 in FY 2020 to 2021 and has since seen a 36.8% increase to 18.5 in FY 2024 to 2025, also shifting to an increasing year-on-year trend. Monthly count of cases by onset highlights these recent increases by onset status (Figure 49).

Table 15. CDI counts and rates, England, by financial year: April 2007 to March 2025

Financial year [note 1]	Mid-year population [note 2]	All reported cases	Rate (all reported cases per 100,000 population)	Total bed-days	Hospital-onset cases	Rate (hospital-onset cases per 100,000 bed-days)	Community-onset cases	Rate (community-onset cases per 100,000 population)
2007 to 2008	51,594,959	55,498	107.6	37,346,236	35,277	94.5	20,221	39.2
2008 to 2009	51,803,017	36,095	69.7	37,718,582	21,338	56.6	14,757	28.5
2009 to 2010	52,306,371	25,604	49.0	37,330,051	14,316	38.3	11,288	21.6
2010 to 2011	52,757,039	21,707	41.1	35,206,316	11,456	32.5	10,251	19.4
2011 to 2012	53,315,857	18,022	33.8	34,669,499	8,644	24.9	9,378	17.6
2012 to 2013	53,498,224	14,694	27.5	34,633,855	6,681	19.3	8,013	15.0
2013 to 2014	54,030,048	13,362	24.7	34,514,871	5,742	16.6	7,620	14.1
2014 to 2015	54,478,406	14,193	26.1	34,972,728	5,953	17.0	8,240	15.1
2015 to 2016	55,040,935	14,143	25.7	34,752,604	5,907	17.0	8,236	15.0
2016 to 2017	55,256,716	12,848	23.3	35,148,014	5,294	15.1	7,554	13.7
2017 to 2018	55,694,748	13,296	23.9	34,903,075	5,463	15.7	7,833	14.1
2018 to 2019	55,999,864	12,273	21.9	34,538,184	4,869	14.1	7,404	13.2
2019 to 2020	56,369,653	13,213	23.4	34,637,156	5,358	15.5	7,855	13.9
2020 to 2021	56,266,460	12,503	22.2	27,628,155	4,897	17.7	7,606	13.5
2021 to 2022	56,692,394	14,277	25.2	32,905,086	6,035	18.3	8,242	14.5
2022 to 2023	57,112,542	15,563	27.2	35,490,766	7,183	20.2	8,380	14.7
2023 to 2024	57,230,111	16,838	29.4	35,991,392	7,537	20.9	9,301	16.3
2024 to 2025	56,994,974	18,970	33.3	36,195,302	8,430	23.3	10,540	18.5

Note 1: financial year ranges from April of one year to March of the following year.

Note 2: ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Figure 49. Monthly counts of CDI by onset of infection, England, by financial year: April 2007 to March 2025

Seasonal trends

There is no clear seasonal trend in hospital-onset (HO) CDI (occurring in hospital admissions at NHS acute trusts for positive specimens taken on day 3 or more, where the day of admission is considered day one) since FY 2010 to 2011, as observed from the graph (Figure 49 and Table S7 in the accompanying data).

In contrast, community-onset (CO) cases have always shown a peak in the second quarter of the financial year (July to September), with this quarter accounting for nearly one third (29.3%) of cases for FY 2024 to 2025.

Prior trust exposure

Increases have been noted in all 4 categories of prior trust exposure. The count of hospital-onset healthcare-associated (HOHA) cases increased by the greatest amount, from 4,869 in FY 2018 to 2019 to 8,430 in FY 2024 to 2025 (73.1% increase). The number of community-onset healthcare-associated (COHA) cases increased by 42.7% between FY 2018 to 2019 and FY 2024 to 2025 from 2,318 to 3,307. This increase was reflected in the COHA rate, which increased 36.5% over the same period, from 6.0 to 8.2 cases per 100,000 bed-days and day admissions. Community-onset community-associated (COCA) cases saw the second greatest increase of 53.9% in the same period from 3,441 to 5,294 cases. This corresponded to an increase of 51.2% in the rate of COCA incidence from 6.1 to 9.3 cases per 100,000 population. Counts of community-onset indeterminate association (COIA) also increased by 44.1% from 1,335 to 1,924, with an observed increase in the rate of incidence from 2.4 to 3.4 cases per 100,000 population (Table S9 in the accompanying data).

Comparisons between years are only made from FY 2018 to 2019, when prior trust exposure fields became mandatory. Missing data since then has been minimal (zero to 5 cases annually), unlike FY 2017 to 2018, which had 1,758 cases (13.2%) without prior trust exposure information.

Since FY 2018 to 2019 the distribution of cases by prior trust distribution has remained stable. In FY 2024 to 2025, 27.9% of cases were COCA, 17.4% COHA and 44.4% HOHA and 10.1% COIA (Figure 50).

Figure 50. Proportion of prior trust exposure CDI cases, England, by financial year, April 2018 to March 2025

Age and sex distribution

In FY 2007 to 2008 each increasing age group contributed a higher percentage of total CDI cases (Table S2 in the accompanying data). The proportion ranged from 0.3% in those aged 2 to 14 years (both male and female cases), to 9.2% in male cases aged 85 years and over, and 20.5% in female cases of the same age group (Figure 51 and (Table S2 in the accompanying data). In FY 2024 to 2025, the distribution in male and female cases had a marked increase amongst those aged 2 to 14 years in comparison to the FY 2007 to 2008 period. Also, unlike the bacteraemia cases reported in this report, there was a larger percentage of female cases compared to male cases, for all age groups.

In FY 2024 to 2025, female cases aged 85 years and over observed a decline in the percentage of total cases from 20.5% in FY 2007 to 2008 to 14.2% of the cases in FY 2024 to 2025. In contrast, 1.1% of female CDI cases were amongst those aged 2 to 14 years versus the 0.3% in FY 2007 to 2008. Similarly, female CDI cases in those aged 15 to 44 years contributed to 6.1% of the total cases in FY 2024 to 2025, a substantial increase from the 2.8% reported in FY 2007 to 2008. The distribution of male cases in different age groups has remained more consistent between the compared financial years, although the most recent data shows an increase from 0.3% to 1.4% in those aged 2 to 14 years, and a slight decline amongst those aged 75 to 84 years, from 14.5% to 13.4% between both periods.

It is important to note that this only reflects percentages of cases and because of the age and sex structure of the population of England, the incidence rate by age and sex can be very different. For all age and sex analyses, cases in which the age and or sex was missing or recorded as unknown were excluded. In FY 2007 to 2008, the age or sex was reported as unknown for 32 cases, while in FY 2024 to 2025, the age or sex was reported as unknown for one case.

Figure 51. Age and sex distribution of CDI by percentage, England, by financial years: April 2007 to March 2008 and April 2024 to March 2025

The rates have reduced across most age groups for both male and female cases between FY 2007 to 2008 and FY 2024 to 2025. In FY 2007 to 2008, the highest rate of CDI was 1,519.3 and 1,508.3 cases per 100,000 population in male and female cases, respectively, in those 85 years and older. In FY 2024 to 2025, this age group still had the highest rate regardless of patient sex. However, the rate had dropped substantially by FY 2024 to 2025 with 314.3 (79.3% decline) and 305.6 cases per 100,000 population (79.7% decline), for male and female cases, respectively. While the largest reductions have been observed amongst older age groups (aged 45 years and over), the exception is with those aged 2 to 14 years, where a slight increase in rate has been observed in both male and female cases (from 4.6 to 5.8 cases per 100,000 population for male cases and 4.0 to 4.9 cases for female cases).

The sharp decline in the overall all case rate of CDI during FY 2007 to 2008 and FY 2013 to 2014, followed by a period of relative stability, is reflected across most age-sex categories. The sharpest declines, for both male and female cases occurred in ages 45 years and over (Figure 52). Case numbers in the 85 years and over age group declined leading into FY 2020 to 2021 before increasing consecutively for the last 4 financial years. This resulted in an increase from 214.4 to 314.3 per 100,000 population in male cases and from 214.4 to 305.6 cases per 100,000 population in female cases, in FY 2024 to 2025.

Figure 52. Trends in age group and sex rates of CDI cases, England, by financial year: April 2007 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by ethnicity

In FY 2024 to 2025, the observed incidence rate of CDI was highest in the White ethnic group (37.3 cases per 100,000 population) (Figure 53 and (Table S14 in the accompanying data). This was followed by the Black and Asian ethnic groups (15.0 and 14.3 cases per 100,000 population, respectively), and lowest in the Mixed and Other ethnic groups (7.2 and 4.3 cases per 100,000 population, respectively).

Unlike other organisms covered in this report, after adjusting for age, the White ethnic group for CDI remains highest at 34.0 cases per 100,000 population. However, the gap between the White and Asian ethnic groups narrowed, with a rate of 28.3 cases per 100,000 population in FY 2024 to 2025, for the latter. Since FY 2020 to 2021 White, Asian and Black ethnic groups have seen sustained increases in their age-standardised incidence. In FY 2024 to 2025, all ethnic groups experienced the highest age-standardised rates of C. difficile infection since the ethnicity data began in FY 2017 to 2018.

Figure 53. C. difficile infection rate by ethnicity, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by deprivation

In FY 2024 to 2025, there was a moderate relationship between incidence and increasing deprivation from 35.8 cases per 100,000 people living in the 20% most deprived areas versus 31.4 cases per 100,000 people living in the 20% least deprived areas (Figure 54 and (Table S13 in the accompanying data).

However, the age-sex standardised incidence rates showed a far stronger variation of incidence by deprivation (47.4 and 26.6 cases per 100,000 population in the 20% most and 20% least deprived areas, respectively) and sustained increases since FY 2018 in all IMD quintiles.

Figure 54. C. difficile infection rate by deprivation, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Geographic distribution

The crude and age-sex standardised rates are presented across ICBs for FY 2024 to 2025 (Figure 55). Rates were particularly high in the North West, followed by the South West regions. The 3 highest ICBs were Greater Manchester ICB (53.3 cases per 100,000 population), Birmingham and Solihull ICB (46.7 cases per 100,000 population) and Lancashire and South Cumbria ICB (46.5 cases per 100,000 population) (Table S6 in the accompanying data). In contrast, London and the home counties had the lowest rates of CDI: Frimley ICB (21.1 cases per 100,000 population), Surrey Heartlands ICB (23.4 cases per 100,000 population) and North East London ICB (23.5 cases per 100,000 population).

Figure 55. Geographic distribution of CDI rate, England, by Integrated Care Boards, by financial year: April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Mortality

Of the 18,970 CDI cases reported in FY 2024 to 2025, mortality information was available for 99.6% (18,888) of cases (Table S9 in the accompanying data). There were 2,402 deaths within 30 days of a CDI, resulting in a CFR of 12.7%, which was a small decrease from 12.9% in FY 2023 to 2024 (Figure 56). The mortality rate increased from 3.8 to 4.2 deaths per 100,000 population between FY 2023 to 2024 and FY 2024 to 2025.

Figure 56. Case-fatality rate and mortality rate of CDI, England, by financial year: April 2007 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Variation by onset

The mortality rate of CO cases increased from 1.4 to 1.5 deaths per 100,000 population (797 to 833) between FY 2023 to 2024 and FY 2024 to 2025 (Table S11 in the accompanying data). HO cases also showed a similar increase with the mortality rate increasing from 3.8 to 4.3 deaths per 100,000 bed-days (1,377 to 1,570 deaths) between FY 2023 to 2024 and FY 2024 to 2025.

The CFR of HO cases increased from 18.3% to 18.6% between FY 2023 to 2024 and FY 2024 to 2025. While the CFR of CO cases decreased from 8.6% to 7.9%.

Variation by age and sex

The highest mortality rates in male cases were in those aged 85 years and over (78.1 deaths per 100,000 population), followed by those aged 75 to 84 years (27.1 deaths per 100,000 population), with a corresponding CFR of 24.9% and 18.0%, respectively (Table S10 in the accompanying data).

In FY 2024 to 2025, there was an increase in the mortality rate and in the CFR compared to FY 2023 to 2024. Amongst male cases aged 85 years and over, the mortality rate increased from 71.1 to 78.1 deaths per 100,000 population while the CFR increased to 24.9% from 24.6%. Similarly, amongst those aged 75 to 84 years, the mortality rate increased from 21.0 to 27.1 deaths per 100,000 population, with CFR increasing from 15.5% to 18.0%.

For female cases, the mortality rates were also higher in older age groups for FY 2024 to 2025 - 55.3 deaths per 100,000 population (aged 85 years and over) and 18.4 deaths per 100,000 population (aged 75 to 84 years). These equated to CFRs of 18.1% and 12.1% of all cases in those respective age groups. Overall, in comparison to the previous year for female cases, there was an increase in mortality rates but a decrease in case-fatality rates for those aged 75 years and older.

Variation by region

Case-fatality rates in FY 2024 to 2025 were highest in the East of England (14.2%) followed by Midlands (13.3%) and the North East and Yorkshire (13.3%). The CFR remained lowest in London at 10.6% and South West (11.1%) (Table S12 in the accompanying data).

CDI overview of recent increases in cases

Between FY 2007 to 2008 and FY 2013 to 2014, rates of CDI fell rapidly and until FY 2021 to 2022 there have been relatively stable rates of all reported cases. These sharp declines in CDI counts and rates were in part due to initiatives introduced by the NHS and the Department of Health and Social Care (DHSC) in 2007 which included the use of personal protective equipment, cohort nursing and environmental decontamination which were geared towards preventing HCAI in acute care settings and not community settings.

Despite these historic declines in CDI counts and rates, FY 2024 to 2025 saw a sharp rise, marking the sixth consecutive annual increase in the hospital-onset incidence rate since FY 2019 to 2020. This trend reflects a 65.2% increase in rate, from 14.1 to 23.3 infections per 100,000 bed-days since FY 2018 to 2019. The reasons for these increases, both in hospital- and community-onset cases, remain unclear and are under investigation.

UKHSA data from the past 4 years show no significant changes in C. difficile ribotypes, arguing against increases driven by a clonal expansion. Further analysis and discussion of recent trends in CDI are available in the recently published technical report (see CDI technical report).

Historically, CDI was primarily an issue within the hospital setting with around 63.6% infections during FY 2007 to 2008 defined as hospital-onset (occurring on or after day 3 of an acute NHS trust admission, where day of admission is counted as day 1). Many of the interventions aimed at the reduction of CDI rates were targeted at the hospital setting, and as a result the sharp decline that has been observed has disproportionately affected hospital-onset infections compared to community-onset infections. Community-onset cases now constitute the greatest proportion of total CDI cases for the reporting period FY 2024 to 2025 (55.6%). However, the division of cases into hospital-onset and community-onset cases ignores the effect of any prior admissions to hospital which could increase the risk of CDI. For this reason, and to better align surveillance in England with that performed by the European Centre for Disease Prevention and Control (ECDC) and the Centres for Disease Control and Prevention (CDC), information on prior trust exposure was introduced in FY 2017.

The prior trust exposure classification groups cases are based on whether a patient was admitted to the reporting organisation within the past 12 weeks. To align with ECDC and CDC definitions, HOHA infections are now defined as those occurring on or after the third day of an acute NHS trust admission, differing from the historical hospital-onset CDI classification, which was defined as those occurring on or after the fourth day of an acute trust admission. This previous classification was in place for 8 years, with data completion improving significantly from the first to the second year due to changes in the DCS. HOHA cases formed the largest group by the new categorisation method. During FY 2024 to 2025 the number of HOHA (from 5,463 to 8,430) increased to its highest reported since the prior trust exposure surveillance began in FY 2017 to 2018.

However, the counts of cases for community-onset groups have each increased since FY 2017 to 2018. COCA CDI cases have to-date shown a consistent year-on-year increase, rising by 85.2% across this period. The underlying cause of this increase is yet to be determined.

Rates of CDI are highest amongst older age groups, with those aged 85 years and over experiencing the highest rates for both male and female cases. However, the greatest reductions between the FY 2007 to 2008 and FY 2024 to 2025 in the rates of CDI have been observed in both male and female cases in the oldest age groups (aged 65 years and over), although reductions have been observed across most age groups due to the large reductions observed in CDI all case counts over the course of the mandatory surveillance programme. The exception to this is that the distribution in male or female cases had a marked increase in proportion of total cases amongst the aged 2 to 14 years age group in comparison to the FY 2007 to 2008 period. There is little difference in the rates between male and female for CDI cases, although in general incidence in females was higher. This marks a difference in epidemiology between CDI and bacteraemia in which rates are higher amongst male cases for most age groups.

Previous work by UKHSA has indicated an association between higher levels of deprivation and higher rates of CDI and historically, Northern regions saw higher rates compared to Southern regions. During FY 2024 to 2025 the North West and South West still remain areas of high incidence.

The most deprived regions were associated with the highest incidence. However, unlike the bacteraemias covered in this report, the White ethnic group had the highest incidence. It should be noted that mortality rates are also rising with the increase in incidence.

The rate of stool specimens examined for CDI diagnosis have been on a steady incline since FY 2017 to 2018, with the rate in FY 2024 to 2025 of 12.7 per 1,000 population being the highest observed since the start of surveillance.

Several interventions aimed at reducing MRSA rates were also aimed at reducing CDI (the ‘Clean Your Hands’ and Saving Lives campaigns). In addition, targets to reduce CDI cases were introduced in 2008. These aimed to reduce the number of cases reported annually to 30% of the FY 2007 to 2008 baseline count by FY 2010 to 2011, a target that was achieved by FY 2008 to 2009. In addition to the objectives and the ‘Clean Your Hands’ and Saving Lives campaigns, guidance was issued aiming to reduce clindamycin, cephalosporin or fluoroquinolone prescribing, which had been shown to promote the spread of epidemic strains of C. difficile. The resulting reduction in prescribing of fluoroquinolones and cephalosporins was associated with a significant decline in the incidence rate of CDI, as evidenced by this study on the impact of guidelines and enhanced antibiotic stewardship.

Laboratory stool specimens

On a quarterly basis, NHS acute trusts are mandated to report the total number of stool specimens examined and the total number of stool specimens examined for diagnosis of CDI. The stool specimen sampling rate declined from a rate of 30.0 per 1,000 population in FY 2010 to 2011, by FY 2019 to 2020 to 25.6, a 14.7% drop (Figure 57 and Table S16 in the accompanying data). This was followed by a sharper 20.7% decline to 20.3 during the pandemic in FY 2020 to 2021. Since then, the sampling rate has steadily increased, reaching levels higher than FY 2010 to 2011 at 34.1 for FY 2024 to 2025 (Figure 57).

Between FY 2010 to 2011 and FY 2013 to 2014, the rate of stool specimens examined for CDI diagnosis observed a decreasing trend from 12.4 per 1,000 population to 9.6. Subsequently, the rate remained relatively stable until FY 2017 to 2018. After this period of stability, the rate has increased year-on-year from 8.9 to 12.7 per 1,000 population in FY 2024 to 2025, reaching the highest rate of samples tested for CDI diagnosis observed since the start of this data collection.

Figure 57. Trends in the rate of C. difficile specimens examined for CDI diagnosis and rate of overall stool specimens examined, England, by financial year: April 2010 to March 2025

Note: shaded bands indicate 95% CIs.

The proportion of positive CDI tests has shown minor fluctuations since the start of surveillance, with a higher proportion of positive tests in the first 2 years of surveillance, followed by a slight decline (Figure 58 and Table S15 in the accompanying data). There was a minor increase observed during FY 2020 to 2021 (2.8%). The proportion of positive tests has remained stable in the previous 2 years at 2.5% but has shown a slight increase to 2.6% in FY 2024 to 2025. While the sampling rate has increased concurrently with the increase in CDI incidence rates since 2017, this does not appear to have impacted positivity, which has remained relatively stable between 2.4 to 2.8% during this period.

Figure 58. Trends in positivity of stool specimens examined for CDI diagnosis, England, by financial year: April 2010 to March 2025

Note: shaded bands indicate 95% CIs.

Clostridioides difficile ribotyping network (CDRN)

Figure 59 explores the ribotype distribution of CDI cases by considering those CDI cases that linked to at least one CDRN sample and had at least one valid ribotype result.

The ribotype distribution is varied across 750 unique ribotypes in FY 2024 to 2025, with the top 5 most common ribotypes being 015 (11.9%), 002 (11.1%), 014 (9.4%), 005 (9.3%) and 023 (8.0%) and accounting for nearly half (49.7%) of all CDI cases (Figure 59 and (Table S18 in the accompanying data).

The distribution of historically dominant ribotypes has changed over the 17 years of surveillance: ribotype 027 and 026, which were the 2 most common ribotypes in FY 2008 to 2009, at 37.1% and 12.1%, fell to 0.3% and 2.0%, respectively, in FY 2024 to 2025. However, in the last decade, the proportions of the most frequently encountered ribotypes have remained relatively stable, and the rise in Clostridioides difficile cases is not explainable by a clonal rise of a single ribotype.

The range of ribotypes has also broadened over time. In the latest FY 2024 to 2025, the most prevalent ribotype 015 is only observed in 11.9% of cases.

Figure 59. Percentage distribution of valid dominant ribotypes (in FY 2024) from CDI cases that linked to a CDRN sample, England, by financial year, April 2008 to March 2025

Note 1: To focus on the recent epidemiology of dominant ribotypes, we only feature distinct ribotypes which were amongst the top 5 most common in FY 2024 to 2025 (015, 002, 014, 005 and 023); all others are grouped into the ‘Other’ ribotype category. As a result, individual ribotypes - in particular, ribotype 027 which was associated with outbreaks in the earlier years but has since declined - will be grouped under ‘Other’. However, these can be studied in (Table S18 of the accompanying data) that details all 11 ribotypes that have been the top 5 prevalent in any year since FY 2008 to 2009.

Note 2: These proportions are ‘ribotype-specific’ meaning that for each ribotype it is the proportion of cases infected with that ribotype. If cases are infected with multiple ribotypes (although this is rare at approximately 1% of cases), each ribotype will contribute to the numerator of its own ribotype-specific proportions. Therefore, the sum of ribotype-specific proportions will not equal 100%.

Note 3: Caution is advised when interpreting data in FY 2008 to 2009 due to small numbers of linked cases with a valid ribotype (n = 132) involved.

Figure 60 shows the total number of CDRN samples referred for ribotyping and some of those CDRN samples that linked to the reported mandatory surveillance CDI cases by financial year from FY 2008 to 2009 to FY 2024 to 2025. Most linked samples tested during the surveillance period returned a single ribotype result (87.9%), with 1.0% returning 2 ribotypes, and 11.1% returning none (‘not available’). In FY 2024 to 2025, amongst cases which linked to CDRN samples, 397 cases (6.8%) did not have any available ribotype result (‘not available’), due to reasons including a culture negative result or logistical issue with the sample (Table S17 in the accompanying data).

The number of samples referred to the CDRN dropped by 7.0% from 8,884 to 8,259 samples in FY 2024 to 2025 (Figure 60) despite CDI case numbers and testing rates being higher than the previous year.

The percentage of CDI cases that linked to CDRN samples dropped from 35.4% in FY 2023 to 2024 to 30.8% in FY 2024 to 2025. This is the lowest coverage seen since FY 2012 to 2013 (28.3%) and in contrast to the highest seen in FY 2016 to 2017 of 42.4% (Table S17 in the accompanying data).

Although CDRN sample referrals and CDI case-to-CDRN linkage fell in the last year, this year, for those CDI cases that could be linked to a CDI sample (n = 5,839), 93.2% had a valid ribotype result (n = 5,442) (Table S17 in the accompanying data) - similar to last year, this result is an all-time high since records began in FY 2008 to 2009.

Figure 60. Trends in CDRN samples referred and all linked cases or those with a valid ribotype, England, by financial year, April 2008 to March 2025

New and future work

Over the past 4 years (FY 2019 to 2020 onwards) of mandatory surveillance, several areas of interest and research have emerged with particular focus on the changes in epidemiological trends observed during COVID-19.

Please note, all research named below is being conducted by, or in affiliation with, UKHSA colleagues. There is also a wide variety of research being conducted by other academic institutes and bodies, and within the devolved nations.

CDI

The exact reasons for the increase in hospital- and community-onset CDI cases remains unclear. Analysis of ribotype distribution has not identified a particular clonal lineage causing the increase. The extent to which the rise in CDI cases is influenced by increasing sampling rates is unclear, as described in this report and the technical report on increases in CDI.

There is a detailed investigation underway on the increase in CDI, investigating the role of comorbidities, AMR and prescribing trends on CDI prevalence. In addition, a project with University of Oxford Health Protection Research Unit (HPRU) in Healthcare Associated Infections and Antimicrobial Resistance is exploring how sampling rates for CDI and E. coli influence reported infection rates, aiming to model the ‘ideal’ testing rate based on case-mix in acute NHS trusts.

S. aureus

Incidence rates have substantially increased since FY 2020 to 2021 for MRSA and MSSA. Whilst reduced hospital activity during FY 2020 to 2021 may have contributed, an increase in case counts has also been observed in community and hospital settings. MRSA rates have been increasing since FY 2021 to 2022, exceeding pre-COVID-19 levels. MSSA rates have also risen, with community-onset cases being the contributing factor. Hospital-onset cases remain elevated compared to FY 2019 to 2020. Current research focuses on investigating the rise in MSSA bacteraemia, analysing temporal trends and determining any epidemiological and clinical factors contributing to this increase.

E. coli and Klebsiella spp.

In FY 2019 to 2020, there were significant reductions in E. coli bacteraemia, particularly from the community setting. Investigations by the University of Oxford HPRU and UKHSA into the underlying causes of this trend are being undertaken. Bacteraemia due to Klebsiella spp. in contrast to E. coli did not see much of a decline at the start of the COVID-19 pandemic and since then has increased both in terms of prevalence and AMR burden in the years following the pandemic. The reasons for the differing overarching trends in these infections are also being investigated.

There are various urinary tract infection (UTI) projects planned or underway as part of a larger UTI working group.

UKHSA are collaborating with the University of Bristol and NHS England on a 5-year NIHR funded programme called ‘Improving Primary Care Antibiotic Prescribing to Reduce Antibiotic Resistant Urinary Tract Infections (IPAP-UTI)’. The study aims to perform Randomised Controlled Trials (RCTs) to see if primary care prescribing can influence AMR trends.

S. aureus and E. coli

Recent research has compared CFRs of E. coli, MRSA and MSSA bacteraemia at a population-level between Israel and England. During 2018 to 2019 there was statistical evidence that CFRs of MRSA, MSSA, MSSA by HO or CO strata and third-generation cephalosporin-resistant E. coli were higher in Israel than England.

Temkin E, Wulffhart L, Pollington TM, Chudasama D, Schechner V, Nutman A, Schwaber MJ, Carmeli Y. ‘A benchmarking study of thirty-day mortality following Staphylococcus aureus or Escherichia coli bacteremia’ (2025) Journal of Infection.

Health inequalities and geography

Following the introduction 2 years ago to include HCAI surveillance data by ethnicity and deprivation in this report, further exploration was carried out into the 5 bacteraemias with case-fatality estimates by deprivation and mortality in this recent publication:

Mazzella A, Amin-Chowdhury Z, Andrews A, Charlett A, Brown CS, Hope R and Chudasama D. ‘Health inequalities in incidence of bacteraemias: A national surveillance and data linkage study, England, 2018 to 2022’ (2025) Eurosurveillance.

Current research at national and local levels aims to clarify how socioeconomic factors, geography, ethnicity, and antimicrobial resistance influence the prevalence of Gram-negative bacteraemia, Staphylococcus aureus bacteraemia, and C. difficile infections. The wide difference in geographic differences, with some similarities and some disparate trends, warrants considerable further investigation.

There is a planned project to further investigate risk factors and other potential drivers of this disparity by ethnicity and socioeconomic factors.

Paediatrics

After older adults, paediatric groups (particularly male cases) face a significant burden from bacteraemia. Ongoing research aims to characterise the paediatric population and identify socio-economic, microbiological and clinical factors that increase the risk of these infections.

Glossary

Age standardised incidence rate

Populations often differ in their age composition, so sub-populations (for example, integrated care boards (ICBs), ethnic groups, or deprivation quintiles) can have different age distributions. For diseases such as bacteraemia, susceptibility may be higher among neonates and older adults. If crude incidence rates are compared between sub-populations, those with relatively more neonates or older people may appear to have artificially higher rates.

(Direct) age standardisation adjusts for this by incorporating the age distribution of a standard population. Each sub-population’s crude age-specific rates are re-weighted using this standard age profile. The result is the incidence rate that would have occurred in the sub-population if it had the same age distribution as the standard population. This makes fairer comparisons between groups possible. Further information is available on the directly standardised rates which are used in this report.

Age-sex standardised incidence rate

This is an extension of age standardisation. Instead of adjusting only for age, the sub-population’s observed age-sex-specific rates are re-weighted to the standard population’s combined age-sex distribution. The result is the incidence rate that would have occurred in the sub-population if it had the same standard age-sex profile, allowing for more equitable comparisons across groups where both age and sex distributions differ.

Average

Scientifically speaking, this is a measure of location. It is a way of summarising the data while reducing the influence of extreme values. There are 3 main statistics to estimate this ‘average’ value – the mean, mode and median (further described in this glossary). Each of these methods has their own strengths and weaknesses.

Bacteraemia

The presence of bacteria in blood.

Bias

Bias is the systematic deviation of either results or inferences from the real situation.

Case-fatality rate (CFR)

CFR is a measure for comparing survivability of different infections and is expressed as the number of deaths out of all reported cases for that infection, as a percentage.

Confidence interval (CI)

CIs indicate the likely range in which an estimated parameter (such as a mean or rate) is likely to fall. For most scientific studies, it is impractical or impossible to measure every single member of a population and therefore the true population mean cannot be determined. Instead, a representative sample is taken, and the sample mean is used as an estimate of the population mean. Although the sample is intended to be representative, a different sample from the same population may provide a different result simply by chance. A CI, over unlimited repetitions of the sample, should contain the true value of a parameter (such as the true population mean) no less than its CI. It is usual to calculate the 95% CIs. That means that if we were to draw several independent, random samples from the same population and calculate 95% CIs from each of them, then 95% of such CIs would contain the true population mean. If we took 20 samples from the same population and calculated 95% CIs, then 19 of 20 (95%) of these 95% CIs would contain the true population meanwhile 1 of 20 (5%) will not.

Denominator

The lower portion of a rate or ratio quotient. This should reflect the population at risk of developing a disease for a given time (which is one year for this report).

Epidemiology

Study of the occurrence and distribution of events (mostly health-related) in a population.

Gram-negative bacteria

Class of bacteria that do not retain crystal violet stain as used as part of a differential staining technique (called the Gram stain). The Gram stain is used as a way of identifying bacteria and the difference in staining results are due to differences in the bacterial cell wall, which has important implications for antimicrobial usage.

Incidence and incidence rate

New cases of a disease occurring in a study population. An incidence rate is then the number of new cases that occur in a defined population in a defined period of time.

NHS ICBs

An administrative unit of the NHS. NHS England has 4 administrative regions: North of England, Midlands and East of England, London, and South of England. Below these regions are 42 administrative geographies referred to as ICBs.

Mean

The arithmetic mean is the common statistic people regard as ‘average value’. It is calculated by summing all the values in a series and then dividing it by the number of included in the series. Mathematically, this is described by the following formula:

mean = (a1 + a1 + … + an) / n

A real-world example would be if you wanted to calculate the mean amount spent on food shopping over a 4-week period (that is, the average amount per week) having spent £51 in week one, £59 in week 2, £67 in week 3 and £52 in week 4:

mean cost of food per week = (£51 + £59 + £67 + £52) / 4 = £57.25

Median

The median of a series of numbers is the mid-point of that series. This provides a measure of an average value that is less affected by extreme values. The median of the following set of numbers [1, 2, 3] is 2, while the median of the set of numbers [1, 1, 1, 2, 10, 15, 16, 20, 100, 105, 110] is 15. To calculate it, the set of numbers needs to be arranged in order of magnitude and then the median is the number exactly in the middle. If there is an even number of values in a set, then the median value is the arithmetic mean of the 2 central values.

Mode

The mode is the most frequent value in a set of data (numbers or text values). In the following set of numbers [1, 1, 1, 2, 10, 15, 16, 20, 100, 105, 110] the mode is 1 as it was included in the set 3 times, while the other numbers were only included once.

Rate ratio

The rate ratio is the quotient of 2 rates. For example, if the rate of MRSA bacteraemia were 2 per 100,000 population in a year amongst male cases, and 4 per 100,000 population in a year amongst female cases, the female-male rate ratio would be 2.0 as the rate would be 2 times higher amongst female than male cases.

Data sources and methodology

The HCAI DCS is a web portal designed by UKHSA to collect an enhanced data set.

Trusts using the website have access to all the data they have entered, which enables them to assess their burden of these HCAIs. This can be compared to a regional and national aggregate total also available to trusts from the website. Clinical commissioning groups (sub-ICBs), local authorities, ICBs, and directors of public health (DPH) are also able to register as users, allowing them to access data specific to their patients.

The data set to be collected is described in the mandatory HCAI surveillance protocol available on the same site. Case unlocks can be requested by reporting organisations using the process described in the Unlock Requests User Guide. Revisions to data is covered by a data-specific revisions and correction policy.

An R package for working with data downloaded from the DCS can be found on GitHub.

For further information on the methodology used to analyse data in this report, please refer to our QMI report.

Inclusion criteria for reporting to the surveillance system

MRSA bacteraemia

The following positive blood cultures must be reported to UKHSA, for the mandatory MRSA surveillance: all cases of bacteraemia caused by S. aureus resistant to meticillin, oxacillin, cefoxitin or flucloxacillin.

MSSA bacteraemia

The following positive blood cultures must be reported to UKHSA, for the mandatory MSSA surveillance: all cases of bacteraemia caused by S. aureus which are susceptible to meticillin, oxacillin, cefoxitin, or flucloxacillin, that is, not subject to MRSA reporting.

E. coli, Klebsiella spp. and P. aeruginosa bacteraemia

The following E. coli, Klebsiella spp. and P. aeruginosa positive blood cultures must be reported to UKHSA: all laboratory-confirmed cases of bacteraemia (including Klebsiella aerogenes), except cases identified post-mortem.

C. difficile infection

Any of the following defines a C. difficile infection in patients aged 2 years and over and must be reported to UKHSA:

diarrhoea stools (Bristol Stool types 5 to 7) where the specimen is C. difficile toxin positive
toxic megacolon or ileostomy where the specimen is C. difficile toxin positive
pseudomembranous colitis revealed by lower gastro-intestinal endoscopy or Computed Tomography
colonic histopathology characteristic of C. difficile infection (with or without diarrhoea or toxin detection) on a specimen obtained during endoscopy or colectomy
faecal specimens collected post-mortem where the specimen is C. difficile toxin positive or tissue specimens collected post-mortem where pseudomembranous colitis is revealed or colonic histopathology is characteristic of C. difficile infection

Background information

This report outlines the latest trends and developments in Gram-negative bacteraemia and C. difficile infections. It aims to provide valuable insights into the incidence, prevalence and future work related to these infections, contributing to the ongoing efforts to enhance patient safety in healthcare settings.

Throughout this report, ‘financial year’ is abbreviated to ‘FY’ and refers to the period between 1 April to 31 March in the years stated.

Prior exposure

In April 2017, the mandatory surveillance programme began capturing information on whether a patient with CDI had previously been admitted to the same reporting trust within the past 84 days (12 weeks). With the prior trust exposure, cases are split into specific groups, a full definition of these groups can be found in the glossary.

Unlike last year’s report, CDI now matches the bacteraemia in its definition of a hospital-onset or hospital-onset healthcare-associated (HOHA) case being a case detected within a hospital stay that is at least 2 days long, with the day of admission being counted as day one and specimen date occurring on day 3 or after.

In April 2019, the mandatory surveillance programme began capturing mandatory information data on whether a patient with Gram-negative and Staphylococcus aureus bacteraemia had been admitted to the same reporting trust in the previous 28 days. Cases are classified into specific ‘prior trust exposure’ groups, whose definitions can be found in the glossary.

Seasonality

Seasonality was assessed as the number of cases each quarter as a percentage of total cases for the financial year. This analysis was performed separately for hospital-onset and community-onset cases.

Further information and contact details

This publication forms part of the range of accredited official statistics outputs routinely published by UKHSA which also include monthly and quarterly reports on the mandatory surveillance of MRSA, MSSA, E. coli, Klebsiella spp. and P. aeruginosa bacteraemia, and CDI.

Quarterly report output

Further epidemiological analyses by quarter can be found in UKHSA’s quarterly epidemiological commentary.

Monthly report outputs

The following monthly reports are produced by UKHSA:

Gram-negative, MRSA and MSSA bacteraemia and CDI: monthly data trends
E. coli, Klebsiella spp., P. aeruginosa, MRSA and MSSA bacteraemia – counts of total reported, hospital-onset healthcare-associated, community-onset healthcare-associated, community-onset community-associated for each bacteraemia by organisation
CDI – counts of total reported, hospital-onset healthcare-associated, community-onset healthcare-associated, community-onset of indeterminate association, community-onset community-associated CDI by organisation

Feedback and contact information

To provide feedback or for any queries, contact mandatory.surveillance@ukhsa.gov.uk

Accredited official statistics

These official statistics were independently reviewed by the Office for Statistics Regulation in May 2022. They comply with the standards of trustworthiness, quality and value in the Code of Practice for Statistics and should be labelled ‘accredited official statistics’. Accredited official statistics are called National Statistics in the Statistics and Registration Service Act 2007. Further explanation of accredited official statistics can be found on the Office for Statistics Regulation website.

Citation

Please cite this document as follows:

UK Health Security Agency. Annual epidemiological commentary: Gram-negative, MRSA, MSSA bacteraemia and C. difficile infections, up to and including financial year 2024 to 2025. London: UK Health Security Agency, September 2025.

Question 2

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Question 3

Epidemiological analysis of Gram-negative organisms: Escherichia coli bacteraemia

Accepted Answer

Total reports

A total of 43,639 cases of E. coli bacteraemia were reported by NHS acute trusts in England in FY 2024 to 2025, of which 8,397 (19.2%) were hospital-onset (HO) cases (Table S1 in the accompanying data). The total reported cases from FY 2024 to 2025 increased by 3.3% compared to the previous FY 2023 to 2024 (n = 42,246). Over time E. coli rates have increased consistently from FY 2012 to 2013, except for the rate decrease during the COVID-19 pandemic (2020 to 2022).

From FY 2012 to 2013 cases have increased overall by 35.1% (from 32,309 to 43,639 cases) and the incidence rate increased from 60.4 to 76.6 cases per 100,000 population (Figure 2).

This most recent FY sees overall rates still slightly below pre-pandemic levels but higher than the start of surveillance.

Figure 1. Trends in the rate of E. coli bacteraemia, England, by financial year: April 2012 to March 2025

Note: shaded bands indicate 95% confidence intervals (CIs)

Hospital and community-onset cases

Community-onset (CO) rates (cases per 100,000 population) increased year-on-year from 46.3 to 63.7 between FY 2012 to 2013 and FY 2018 to 2019 (Figure 1 and Table 1). Following this increase, CO rates declined for the first time between FY 2019 to 2020 and FY 2020 to 2021, reaching 53.8, coinciding with the beginning of the COVID-19 pandemic, and have since increased to 61.8 in FY 2024 to 2025. This increase was also reflected in episode counts, with 35,242 CO cases reported in FY 2024 to 2025, just below the counts seen before the pandemic.

In contrast, the HO (hospital-onset) rate (cases per 100,000 bed-days) of E. coli cases was relatively stable at around 22.0 between FY 2012 to 2013 and FY 2018 to 2019 apart from a temporary decrease to 21.1 in FY 2014 to 2015 (Table 1). Rates continued to increase from FY 2018 to 2019 to FY 2020 to 2021 (22.1 to 23.6), then declined to 21.5 the following year, but have steadily increased since, reaching 23.2 in FY 2024 to 2025, surpassing FY 2018 to 2019 levels.

Figure 2. Monthly counts of E. coli bacteraemia by onset of infection, England, by financial year: April 2012 to March 2025

Table 1. E. coli bacteraemia counts and rates, England, by financial year: April 2012 to March 2025

Financial year [note 1]	Mid-year population estimate [note 2]	All reported cases	Rate (all reported cases per 100,000 population)	Total bed-days	Hospital-onset cases	Rate (hospital-onset per 100,000 bed-days)	Community-onset cases	Rate (community-onset per 100,000 population)
2012 to 2013	53,498,224	32,309	60.4	34,633,855	7,552	21.8	24,757	46.3
2013 to 2014	54,030,048	34,286	63.5	34,514,871	7,558	21.9	26,728	49.5
2014 to 2015	54,478,406	35,823	65.8	34,972,728	7,382	21.1	28,441	52.2
2015 to 2016	55,040,935	38,315	69.6	34,752,604	7,744	22.3	30,571	55.5
2016 to 2017	55,256,716	40,690	73.6	35,148,014	7,890	22.4	32,800	59.4
2017 to 2018	55,694,748	41,152	73.9	34,903,075	7,688	22.0	33,464	60.1
2018 to 2019	55,999,864	43,290	77.3	34,538,184	7,632	22.1	35,658	63.7
2019 to 2020	56,369,653	43,410	77.0	34,637,156	7,839	22.6	35,571	63.1
2020 to 2021	56,266,460	36,819	65.4	27,628,155	6,530	23.6	30,289	53.8
2021 to 2022	56,692,394	38,050	67.1	32,905,086	7,085	21.5	30,965	54.6
2022 to 2023	57,112,542	38,789	67.9	35,490,766	7,885	22.2	30,904	54.1
2023 to 2024	57,230,111	42,246	73.8	35,991,392	8,171	22.7	34,075	59.5
2024 to 2025	56,994,974	43,639	76.6	36,195,302	8,397	23.2	35,242	61.8

Note 1: financial year ranges from April of one year to March of the following year.

Note 2: Office for National Statistics (ONS) mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Seasonal trends in E. coli bacteraemia

Seasonality was assessed as the number of cases each quarter as a percentage of total cases for the financial year. This analysis was performed separately for hospital-onset and community-onset cases (Table S7 in the accompanying data). In general, community-onset E. coli cases peak in the July to September quarter of every year (for example, summer), a trend that has not changed since April 2012. Historically, there was much less seasonal variation in hospital-onset E. coli cases. However, in FY 2020 to 2021, hospital-onset E. coli cases peaked in October 2020 to December 2020 and January 2021 to March 2021. This was compared with previous years, where it peaked in the July to September quarter. These variations to seasonal trends occurred during the second wave of COVID-19.

Prior trust exposure

In comparison to FY 2020 to 2021, in FY 2024 to 2025 there was an increase in the total count of hospital-onset healthcare-associated (HOHA) E. coli counts from 6,530 to 8,397, with the incidence rate showing a slight decrease from 23.6 to 23.2 cases per 100,000 bed-days. Contributing factors include a slow increase in bed occupancy since the COVID-19 pandemic.

Over the same period, both the count and rate of community-onset healthcare-associated (COHA) E. coli bacteraemia counts increased by 22.4% (from 5,127 to 6,277) and rates decreased by 7.7% (from 16.9 to 15.6 cases per 100,000 bed-days and day admissions), respectively.

Increases were seen in both the counts and rates of community-onset community-associated (COCA) cases, for the same period, from 24,816 to 28,938 cases (an increase of 16.6%) and from 44.1 to 50.8 (an increase of 15.1%) cases per 100,000 population, respectively (Table S8 in the accompanying data).

Since FY 2020 to 2021 the distribution of cases by prior trust distribution has remained stable. In FY 2024 to 2025, 66.3% of cases were COCA, 14.4% COHA and 19.2% HOHA (Figure 3). Caution is advised when comparing with FY 2019 to 2020 prior trust exposure distribution for community-onset cases within Table S8 in the accompanying data. During this period, the number reported with no information on prior trust exposure was 5,153; however, subsequently when the relevant fields became mandatory from late 2019, this resulted in a sharp decline in missing data, with sporadic counts ranging from zero to 2 in subsequent years.

Figure 3. Proportion of prior trust exposure of E. coli bacteraemia cases, England, by financial year, April 2020 to March 2025

Age and sex distribution

Broadly, the age and sex distribution of E. coli cases in FY 2012 to 2013, at the start of surveillance, versus FY 2024 to 2025 of cases was similar (Figure 4 and Table S2 in the accompanying data) . The greatest burden of infection remains in adults aged 45 years and over; within this demographic, male and female cases aged 75 to 84 years have the highest proportion of cases, comprising 16.2% of male and 14.1% of female total cases (FY 2024 to 2025), respectively.

The percentage distribution of cases amongst male and female cases were similar across age groups, except in those aged 15 to 44 years, where cases were approximately 3 times higher in female cases compared to male cases in both presented financial years. For all age and sex analyses, cases for which the sex or age was missing or reported as ‘unknown’ were excluded.

Figure 4. Age and sex distribution of E. coli bacteraemia by percentage of cases, England, by financial years: April 2012 to March 2013 and April 2024 to March 2025

The incidence rate increased in most age groups, for male and female cases between FY 2012 to 2013 and FY 2024 to 2025.

In FY 2024 to 2025, both male and female cases had the highest rates amongst individuals aged 85 years and over at 895.7 and 578.5 cases per 100,000 population, respectively. In this period, the rate ratio between men and woman consistently increased with age in all those age groups containing individuals aged 45 years and over. This was also consistent with FY 2012 to 2013.

Compared to the last financial year, FY 2024 to 2025 displayed a 19.7% decline in infection rates for male cases in the under one year age group and a 22.8% increase for female cases. There was a slight increase in rates in those aged 45 years and over for both male and female cases (Figure 5).

In the last 4-year period post-pandemic (from April 2021 to March 2025), the rate in male cases aged 85 years and over increased by 12.1% from 798.8 to 895.7 cases per 100,000 population. The rate amongst those aged 75 to 84 years increased by 13.5%, from 366.9 to 416.2 cases per 100,000 population.

During the same post-pandemic period between FY 2021 to 2022 and FY 2024 to 2025, increases were also observed in female cases, in the 85 years and over age group, an increase of 13.0% was observed, rising from 512.1 to 578.5 cases per 100,000 population. Similarly, those aged 75 to 84 years displayed an increase of 15.6% since FY 2021 to 2022 (264.1 to 305.2).

All other age groups showed varying degrees of fluctuation but remained relatively low (less than 200.0 cases per 100,000 population) in FY 2024 to 2025.

Figure 5. Trends in age group and sex rates of E. coli bacteraemia, England, by financial year: April 2012 to March 2025

Note: shaded bands indicate 95% CIs.

The rates of E. coli bacteraemia broadly increased between FY 2012 to 2013 and FY 2018 to 2019. This was followed by a large decline between the April 2020 and March 2021 period due to the pandemic. In FY 2024 to 2025, there was an increase in rate in most age groups and in both male and female cases. The highest increase in rate, when compared to FY 2023 to 2024, was in male cases (7.1%) aged 45 to 64 years, while female cases in this age group showed a 1.5% rise in rates. This was followed by those aged 65 to 74 years, with increases of 6.3% in male cases and 4.8% in female cases.

Caution is advisable when interpreting data for E. coli amongst those aged 1 to 14 years as the number of cases is too small to interpret trends well.

Cases with missing age or sex was rare and reduced over the surveillance period, with 51 cases in FY 2012 to 2013, versus 2 cases in FY 2024 to 2025.

Trends by ethnicity

In FY 2024 to 2025, the observed incidence rate of E. coli bacteraemia was highest in the White ethnic group (79.2 cases per 100,000 population), followed by the Asian and Black ethnic groups (56.6 and 53.0 cases per 100,000 population, respectively) (Figure 6 and Table S14 in the accompanying data) . It was lowest in the Other and Mixed ethnic groups (20.4 and 18.9 cases per 100,000 population, respectively).

The age-standardised incidence rate saw the highest incidence rates in the Asian and Black ethnic groups (118.4 and 96.6 cases per 100,000 population, respectively) versus the White ethnic group (71.6 cases per 100,000 population). Rates in the Asian and Black ethnic groups increased sharply year-on-year from FY 2020 to 2021. In FY 2024 to 2025, Asian, Black and Other ethnic groups experienced the highest age-standardised rates of E. coli bacteraemia since April 2017.

Figure 6. E. coli bacteraemia rate by ethnicity, England, by financial year: April 2018 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by deprivation

In FY 2024 to 2025, 82.2 cases occurred per 100,000 people living in the 20% most deprived areas versus 68.3 cases per 100,000 people living in the 20% least deprived areas (Figure 7 and Table S13 in the accompanying data). The observed incidence rate of E. coli bacteraemia generally increased with deprivation.

The variation in age-sex standardised incidence rates of E. coli was much greater or lower than that observed (100.4 and 56.4 cases per 100,000 population) in the 20% most or 20% least deprived areas, respectively, suggesting the risk is doubled between these 2 indices of multiple deprivation (IMD) quintiles. Also noted is that the gap between the various deprivation levels is much wider for age-sex standardised data even though the ranking does not necessarily change. All IMD quintiles have seen increases in age-sex standardised rates in the last financial year. There has been a consistent ordering of age-sex standardised E. coli time series by increasing deprivation since April 2017.

Figure 7. E. coli bacteraemia rate by deprivation, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Primary focus of E. coli bacteraemia

The provision of data on the most likely primary focus of E. coli bacteraemia is voluntary. The percentage of cases where this information has been provided has declined over time from 85.5% (n = 27,610) in FY 2012 to 2013 to 49.7% (n = 21,707) in FY 2024 to 2025 (Table 2), with a 1.2% decrease versus FY 2023 to 2024 (n = 21,981) (Table S4 in the accompanying data).

Of cases with a reported primary focus of infection, urinary tract has consistently been the most frequent primary focus for E. coli bacteraemia cases. In FY 2012 to 2013 48.9% of cases reported a most likely primary focus of urinary tract, and by FY 2024 to 2025, 46.3% (n = 10,056). Hepatobiliary as a primary focus has slightly increased between FY 2012 to 2013 and FY 2024 to 2025 from 13.6% to 15.7%. The percentage of records for which the primary focus was reported as unknown has decreased from 20.2% in FY 2012 to 2013 to 17.5% in FY 2024 to 2025. All other reported primary focus rates have remained relatively unchanged between FY 2012 to 2013 and FY 2024 to 2025 apart from a change from 3.8% to 6.1% for respiratory tract.

Table 2. E. coli bacteraemia counts and percentages by primary focus of bacteraemia, England, by financial year: April 2012 to March 2025

Financial year [note 1]	Total E. coli reported	Primary focus ascertained: (number)	Primary focus ascertained: (%)	Gastro-intestinal [note 2]: (number)	Gastro-intestinal (% [note 2])	Hepatobiliary: (number)	Hepatobiliary: (%)	Urinary tract: (number)	Urinary tract: (%)	Respiratory tract: (number)	Respiratory tract: (%)	Other [note 3] : (number)	Other (% [note 3])	Unknown: (number)	Unknown (%)
2012 to 2013	32,309	27,610	85.5%	1,782	6.5%	3,756	13.6%	13,501	48.9%	1,050	3.8%	1,936	7.0%	5,585	20.2%
2013 to 2014	34,286	28,300	82.5%	1,711	6.0%	3,855	13.6%	13,393	47.3%	1,016	3.6%	1,873	6.6%	6,452	22.8%
2014 to 2015	35,823	28,729	80.2%	1,640	5.7%	3,818	13.3%	13,088	45.6%	1,099	3.8%	1,851	6.4%	7,233	25.2%
2015 to 2016	38,315	26,446	69.0%	1,492	5.6%	3,556	13.4%	12,220	46.2%	1,068	4.0%	1,703	6.4%	6,407	24.2%
2016 to 2017	40,690	22,727	55.9%	1,237	5.4%	3,277	14.4%	10,727	47.2%	1,028	4.5%	1,553	6.8%	4,905	21.6%
2017 to 2018	41,152	25,616	62.2%	1,717	6.7%	4,035	15.8%	12,566	49.1%	1,575	6.1%	1,757	6.9%	3,966	15.5%
2018 to 2019	43,290	28,469	65.8%	1,969	6.9%	4,687	16.5%	13,914	48.9%	1,728	6.1%	1,989	7.0%	4,182	14.7%
2019 to 2020	43,410	27,515	63.4%	1,774	6.4%	4,351	15.8%	13,241	48.1%	1,674	6.1%	1,898	6.9%	4,577	16.6%
2020 to 2021	36,819	20,395	55.4%	1,352	6.6%	3,721	18.2%	8,972	44.0%	1,251	6.1%	1,524	7.5%	3,575	17.5%
2021 to 2022	38,050	18,636	49.0%	1,328	7.1%	3,108	16.7%	8,393	45.0%	1,092	5.9%	1,489	8.0%	3,226	17.3%
2022 to 2023	38,789	18,448	47.6%	1,268	6.9%	2,859	15.5%	8,316	45.1%	1,053	5.7%	1,597	8.7%	3,355	18.2%
2023 to 2024	42,246	21,981	52.0%	1,404	6.4%	3,400	15.5%	9,892	45.0%	1,280	5.8%	1,907	8.7%	4,098	18.6%
2024 to 2025	43,639	21,707	49.7%	1,503	6.9%	3,408	15.7%	10,056	46.3%	1,315	6.1%	1,621	7.5%	3,804	17.5%

Note 1: financial year from April to March of the following year.

Note 2: gastrointestinal (not hepatobiliary).

Note 3: ‘Other’ includes the following options inputted on the HCAI DCS: bone and joint, central nervous system, genital tract (including prostate), indwelling intravascular device, other, respiratory tract, skin or soft tissue, no clinical signs of bacteraemia.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, the primary focus of E. coli bacteraemia also varied according to time-to-onset (duration between hospital admission and date of a positive specimen) (Table 3). Urinary tract as the primary focus was the most reported amongst time to-onset-groups. Furthermore, urinary tract as a primary focus was more common in cases where the time-to-onset was less than 2 days (49.3%) versus 2 and 6 days (33.8%) and 7 days or greater (37.6%).

Table 3. Distribution of primary focus E. coli bacteraemia, by time-to-onset, England, by financial year: April 2024 to March 2025

Time to onset (days) [note 1]	Gastrointestinal (not hepatobiliary) (number)	Gastrointestinal (not hepatobiliary) (%) [note 2]	Hepatobiliary (number)	Hepatobiliary (%) [note 2]	Urinary tract (number)	Urinary tract (%) [note 2]	Respiratory tract (number)	Respiratory tract (%) [note 2]	Other (number)	Other (%) [note 2]
Less than 2	540	6.3%	1,405	16.3%	4,238	49.3%	377	4.4%	575	6.7%
2 to 6	200	13.0%	314	20.3%	522	33.8%	78	5.1%	152	9.9%
7 and over	349	11.5%	362	11.9%	1,143	37.6%	192	6.3%	420	13.8%

Note 1: number of days from admission to positive bacteraemia sample (if both are on the same date the difference would be zero days).

Note 2: proportion of cases by primary focus.

Geographic distribution

The crude and age-sex standardised rates is presented across integrated care boards (ICBs) for FY 2024 to 2025, of which there was considerable geographical variation in rates of E. coli bacteraemia (Figure 8). Age-sex standardised rates (cases per 100,000 population) indicate high incidence in London, Northern and Midlands regions, specifically North-East London ICB (107.1), South Yorkshire ICB (99.0), Frimley ICB (97.8) and Nottingham and Nottinghamshire ICB (96.0) (Table S6 in the accompanying data). The lowest incidence rates were observed in Gloucestershire ICB (32.2), Bath and North-East Somerset, Swindon and Wiltshire ICB (56.5) and Herefordshire and Worcestershire ICB (58.1).

Figure 8. Geographic distribution of E. coli bacteraemia rate, by Integrated Care Boards, England, by financial year: April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Mortality

In FY 2024 to 2025, 43,639 E. coli bacteraemia cases were reported in England. Information on mortality was available for 99.1% (43,233) of these cases (Table S9 in the accompanying data). There were 6,342 deaths within 30 days of an E. coli bacteraemia diagnosis, a mortality rate of 11.1 deaths per 100,000 population and a case-fatality rate (CFR) of 14.6% (Figure 9).

Similar to previous reports, there was a declining trend in CFR from the beginning of surveillance (FY 2012 to 2013, CFR: 16.8%), until FY 2018 to 2019 (CFR: 13.8%), after which the CFR increased to 16.1% by FY 2020 to 2021. Over the past 4 years, the CFR trend has fluctuated, with a marginal decline over the last 2 years, resulting in a current CFR of 14.6% for FY 2024 to 2025. The mortality rate increased slightly between FY 2023 to 2024 and FY 2024 to 2025, rising from 10.7 to 11.1 deaths per 100,000 population, contrasting with the slight decrease observed in the previous year.

Figure 9. Case-fatality rate and mortality rate of E. coli bacteraemia, England, by financial year: April 2012 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Variation by onset of bacteraemia

Following the decline observed in FY 2021 to 2022 when community-onset (CO) mortality rate was 7.2, mortality rate has since increased to 7.9 deaths per 100,000 population (Table S11 in the accompanying data). Hospital-onset (HO) rates increased from 4.9 to 5.1 deaths per 100,000 population during the same period.

Both HO CFR and CO CFR saw modest declines between FY 2012 to 2013 and FY 2024 to 2025, with HO CFR decreasing from 23.6 to 21.9% and CO CFR from 14.8 to 12.8%. The HO CFR remained 1.5 to 1.8 times higher than CO CFR throughout the period.

Variation by age and sex

In FY 2024 to 2025, amongst male cases, the highest mortality rates were observed in those aged 85 years and over (208.5 deaths per 100,000 population) and aged 75 to 84 years (68.6 deaths per 100,000 population) (Table S10 in the accompanying data). This equated to CFRs of 23.3% and 16.5%, respectively, indicating a slight increase in those aged 85 years and over but a decrease in those aged 75 to 84 years from the previous FY 2023 to 2024 which recorded CFRs of 22.8% and 17.2%, respectively. The mortality rate for both groups increased by 7.8% and 0.3%, from the previous year, respectively.

Similar to male cases, the highest mortality rates in female cases in FY 2024 to 2025 was seen in those aged 85 years and over at 104.5 deaths per 100,000 population, followed by those aged 75 to 84 years at 42.6. This equated to CFRs of 18.1% and 14.0% of cases, respectively.

Numbers of deaths are small in some of the younger groups so differences should be interpreted with caution.

Variation by region

Case-fatality rates in FY 2024 to 2025 were broadly similar across the country, being highest in the Midlands region (16.1%) followed by East of England (14.9%) and North West (14.9%) (Table S12). The CFR remained lowest in London (12.6%), the South West (13.6%) and South East of England (14.3%).

Question 4

Epidemiological analysis of Gram-negative organisms: Klebsiella spp. bacteraemia

Accepted Answer

Total reports

A total of 13,438 cases of Klebsiella species (Klebsiella spp.) bacteraemia were reported by NHS acute trusts in England in FY 2024 to 2025, an increase of 2.5% from FY 2023 to 2024 (n = 13,111), marking a steady annual increase in cases since the substantial 10.5% rise between FY 2022 to 2023 and FY 2023 to 2024 (Table S1 in the accompanying data). Of these, 4,185 (31.1%) were hospital-onset cases (Figure 11). The total count of Klebsiella spp. bacteraemia has increased year-on-year since the start of surveillance (FY 2017 to 2018) from 9,823 to 13,438. This increase was also reflected in the incidence rate of total Klebsiella spp. bacteraemia cases, which increased from 17.6 cases per 100,000 population in FY 2017 to 2018 to 23.6 in FY 2024 to 2025.

Figure 10. Trends in the rate of Klebsiella spp. bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Hospital and community-onset cases

Community-onset rates (CO) have increased from 12.4 cases per 100,000 population in FY 2017 to 2018 to 14.0 in FY 2019 to 2020 (Figure 10 and Table 4). Following this increase, CO rates declined in FY 2020 to 2021, reaching 13.2. Since then, CO counts and rates have seen a rapid increase, increasing from 7,917 and 13.9 in FY 2022 to 2023 to 9,123 and 15.9 in FY 2023 to 2024, respectively. This upward trend has continued for FY 2024 to 2025, maintaining a steady increase to 9,253 and 16.2.

The rate (cases per 100,000 bed-days) of hospital-onset (HO) Klebsiella spp. cases was 8.4 in FY 2017 to 2018 increasing to 13.8 by FY 2020 to 2021. This observed increase has 2 components. Firstly, the number of HO cases increased from 3,233 to 3,803 between April 2019 and March 2021. Secondly, there was a drop off in hospital activity (occupied bed-days) between April 2019 and March 2021 which resulted in increased rates.

Hospital activity has since increased, contributing to the decrease in HO rate to 11.3 in FY 2021 to 2022 and 11.1 in FY 2023 to 2024, despite an increase in case numbers. The rate for FY 2024 to 2025 was 11.6, a minor increase compared to the previous year.

Figure 11. Monthly counts of Klebsiella spp. bacteraemia by onset of infection, England, by financial year: April 2017 to March 2025

Table 4. Klebsiella spp. bacteraemia counts and rates, England, by financial year: April 2017 to March 2025

Financial year [note 1]	Mid-year population estimate [note 2]	All reported cases	Rate (all reported cases per 100,000 population)	Total bed-days	Hospital-onset cases	Rate (hospital-onset cases per 100,000 bed-days)	Community-onset cases	Rate (community-onset cases per 100,000 population)
2017 to 2018	55,694,748	9,823	17.6	34,903,075	2,937	8.4	6,886	12.4
2018 to 2019	55,999,864	10,739	19.2	34,538,184	3,217	9.3	7,522	13.4
2019 to 2020	56,369,653	11,097	19.7	34,637,156	3,233	9.3	7,864	14.0
2020 to 2021	56,266,460	11,204	19.9	27,628,155	3,803	13.8	7,401	13.2
2021 to 2022	56,692,394	11,452	20.2	32,905,086	3,711	11.3	7,741	13.7
2022 to 2023	57,112,542	11,865	20.8	35,490,766	3,948	11.1	7,917	13.9
2023 to 2024	57,230,111	13,111	22.9	35,991,392	3,988	11.1	9,123	15.9
2024 to 2025	56,994,974	13,438	23.6	36,195,302	4,185	11.6	9,253	16.2

Note 1: financial year ranges from April of one year to March of the following year.

Note 2: ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Seasonal trends

The seasonal trends in hospital-onset and community-onset cases in FY 2024 to 2025, was similar to that seen before the pandemic (FY 2017 to 2018 and FY 2020 to 2021). Across hospital-onset, community-onset and all cases, the percentage of yearly infections was generally higher during the July to September quarter, and lower in the last 2 financial quarters (Table S7 in the accompanying data).

Distribution of Klebsiella species

In FY 2024 to 2025 Klebsiella pneumoniae (75.1%) was the most frequently reported species, followed by Klebsiella oxytoca (15.4%). This distribution was similar regardless of onset of infection (Table 5). Compared with FY 2023 to 2024, the largest rise in Klebsiella spp. was seen in Klebsiella pneumoniae (4.7%). This is notably lower than the 12.0% increase seen in FY 2023 to 2024 compared to FY 2022 to 2023, marking a slowdown in the rate of increase in the latest year.

Table 5. Counts and percentages of Klebsiella species bacteraemia, England, by financial year: April 2024 to March 2025

Species	All cases	Proportion of all cases	Hospital-onset cases	Proportion of all cases (hospital-onset)	Community-onset cases	Proportion of all cases (community-onset)
K. pneumoniae	10,095	75.1%	3,100	30.7%	6,995	69.3%
K. oxytoca	2,064	15.4%	616	29.8%	1,448	70.2%
K. aerogenes	505	3.8%	235	46.5%	270	53.5%
Other named species	443	3.3%	130	29.3%	313	70.7%
Not speciated	331	2.5%	104	31.4%	227	68.6%

Prior trust exposure

Between FY 2020 to 2021 and FY 2024 to 2025 there was an increase in the count of hospital-onset healthcare-associated (HOHA) cases, from 3,803 to 4,185, but a drop in the HOHA incidence rate, from 13.8 cases per 100,000 bed-days to 11.6 (Table S8 in the accompanying data).

Community-onset healthcare-associated (COHA) Klebsiella spp. cases have remained broadly similar to HOHA cases since FY 2020 to 2021: an increase was observed in FY 2024 to 2025 with counts reaching 1,995, a 32.1% increase from FY 2020 to 2021 and 4.0% from the previous financial year (FY 2023 to 2024). The rate of COHA cases fell slightly by 0.4% from 5.0 to 5.0 cases per 100,000 bed-days and day-admissions compared to FY 2020 to 2021.

Between FY 2020 to 2021 and FY 2024 to 2025, the number of cases and rate of community-onset community-associated (COCA) Klebsiella spp. bloodstream infection (BSI) incidence increased on average annually, respectively, by 6.0% (from 5,839 to 7,246) and by 5.6% (from 10.4 to 12.7 cases per 100,000 population). This increase is more notable between FY 2022 to 2023 and FY 2023 to 2024, when the count and rate increased by 14.8% and 14.5% from 6,246 to 7,168 and 10.9 to 12.5, respectively. For FY 2024 to 2025 the count and rate increase from the previous year saw a slowdown to 1.1% (from 7,168 to 7,246) and 1.5% (from 12.5 to 12.7), respectively.

Since FY 2020 to 2021 the distribution of cases by prior trust distribution has seen small changes in COCA cases from 52.1% to 53.9% and COHA cases from 13.5% to 14.8% while HOHA cases have decreased from 33.9% to 31.1% (Figure 12).

These comparisons should be interpreted with caution as FY 2019 to 2020 had 1,009 cases without prior trust exposure data, which became mandatory in late 2019, and therefore may underestimate the proportion of COHA and COCA cases, compared with one case in FY 2020 to 2021 and zero cases in subsequent years.

Figure 12. Proportion of prior trust exposure of Klebsiella spp. cases, England, by financial year, April 2020 to March 2025

Age and sex distribution

For all age and sex analyses, cases in which the age and/or sex was missing or recorded as unknown were excluded. In FY 2017 to 2018, only one case was reported with ‘unknown’ age or sex versus zero cases of ‘unknown’ age or sex in FY 2024 to 2025 (Table S2 in the accompanying data).

Broadly, the age and sex distribution of Klebsiella spp. bacteraemia cases as a percentage of all reported cases in FY 2017 to 2018 compared to FY 2024 to 2025 remains similar, with most of the burden of infection being amongst male cases (Figure 13). In FY 2024 to 2025, the case burden remained highest in male cases aged 45 years and over, predominantly amongst those aged 75 to 84 years (19.3% of total cases). A similar trend was seen in older female cases aged 45 to 64 years (9.2% of total cases) and aged 75 to 84 years (8.9% of total cases), but to a much lesser extent. This is consistent with what has been observed in FY 2017 to 2018.

Figure 13. Age and sex distribution of Klebsiella spp. bacteraemia by percentage of cases, England, by financial years: April 2017 to March 2018 and April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, the incidence rates of Klebsiella spp. bacteraemia were greater in male cases compared to female cases, particularly amongst those aged 45 years and over. The incidence rate increased in all age groups, for male and female cases, between FY 2017 to 2018 and FY 2024 to 2025.

In FY 2024 to 2025, both male and female cases had their highest rates amongst individuals aged 85 years and over at 297.4 and 88.9 cases per 100,000 population, respectively.

Trends in the age-specific and sex-specific rates of Klebsiella spp. bacteraemia are shown in Figure 14. Rates of Klebsiella spp. bacteraemia have increased across most age and sex groups between the start of the surveillance in FY 2017 to 2018 until FY 2019 to 2020. These increases were notable in male cases aged 75 years and over, and to a lesser extent female cases aged 75 years and over. Sharp declines were observed in these older age groups, in FY 2020 to 2021, which began to increase again in the following financial year. In FY 2024 to 2025, an increase in these older male age groups was noted compared to the previous financial year, increasing by 4.5%, from 146.5 to 153.0 cases per 100,000 population in 75 to 84 years, and by 6.3%, from 279.9 to 297.4 cases per 100,000 population in the 85 years and older group. Unlike male cases aged 85 years and over group, which has seen year-on-year increases in rate since FY 2020 to 2021, female cases in the same age group have seen rates decrease by 7.3%, from 95.8 to 88.9 cases per 100,000 population in FY 2024 to 2025 compared to the previous year. Whereas female cases aged 75 to 84 years, saw an increase by 4.5%, from 56.8 to 59.3 cases per 100,000 population in FY 2024 to 2025 compared to the previous year.

The incidence rate in those aged under one year declined by 5.6% for female cases and 4.7% for male cases since the previous FY 2023 to 2024. Since last year, there was also a decline in the rate amongst those aged between one to 14 years, with a 9.5% decrease in male cases (from 1.9 to 1.7) but female cases remained the same at 1.4 per 100,000 population.

The numbers remain low for the zero to 14 age groups so interpreting long-term trends should be done with caution. For all age and sex analyses, cases in which the age and/or sex was missing or recorded as unknown were excluded. In FY 2017 to 2018, only one case was reported with ‘unknown’ age or sex versus zero cases of ‘unknown’ age or sex in FY 2024 to 2025.

Figure 14. Trends in age group and sex rates of Klebsiella spp. bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by ethnicity

In FY 2024 to 2025, the observed incidence rate of Klebsiella spp. bacteraemia were highest in the Black and White ethnic groups (24.1 and 23.7 cases per 100,000 population, respectively), intermediate in the Asian ethnic group (18.9 cases per 100,000 population), and lowest in the Mixed and Other ethnic groups (7.5 and 6.9 cases per 100,000 population, respectively) (Figure 15 and Table S14 in the accompanying data).

However, age-standardised incidence rates were substantially higher in those of Black ethnicity (41.5), followed by Asian ethnicity (37.9), whereas incidence rate in the White ethnic group was amongst the lowest (21.5). Since April 2021, there were sharper rises in Black and Asian ethnic groups.

Figure 15. Klebsiella spp. bacteraemia rate by ethnicity, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by deprivation

In FY 2024 to 2025, 26.5 cases occurred per 100,000 people living in the 20% most deprived areas versus 20.4 cases per 100,000 people living in the 20% least deprived areas (Figure 16 and Table S13 in the accompanying data). The observed incidence rate of Klebsiella spp. bacteraemia increased with deprivation.

The range between deprivation quintiles was amplified when age-sex standardised incidence of Klebsiella spp. was used. With the standardised rates, the 20% most and 20% least deprived quintiles had respective rates of 34.8 and 17.0 cases per 100,000 population, the range of these is more than double the range for observed incidence rates. There was a continued rise in incidence rate across IMD quintiles from FY 2022 to 2023 to FY 2024 to 2025, except for the past year where the 40% to 60% quintile saw a more moderate increase. There has been a consistent ordering of age-sex standardised Klebsiella spp. bacteraemia time series by increasing deprivation since April 2018.

Figure 16. Klebsiella spp. bacteraemia rate by deprivation, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Primary focus of Klebsiella spp. bacteraemia

Reporting of primary focus for Klebsiella spp. bacteraemia remains low. In FY 2024 to 2025 the primary focus was reported for 45.4% of all cases (Table 6 and Table S4 in the accompanying data). The most frequently reported primary focus of Klebsiella spp. bacteraemia was the urinary tract, constituting 36.4% of cases with a reported primary focus of infection in FY 2024 to 2025. This percentage has remained broadly consistent since the inception of Klebsiella spp. surveillance in FY 2017 to 2018. Hepatobiliary and respiratory tract as primary foci have decreased between FY 2017 to 2018 and FY 2024 to 2025, from 20.2% to 17.1% and from 9.2% to 9.1%, respectively.

Table 6. Klebsiella spp. bacteraemia counts and rates by primary focus of bacteraemia, England, by financial year: April 2017 to March 2025

Financial year [note 1]	Total Klebsiella spp. reported	Primary focus ascertained: (number)	Primary focus ascertained: (%)	Gastro-intestinal [note 2] : (number)	Gastro-intestinal (% [note 2])	Hepatobiliary: (number)	Hepatobiliary: (%)	Urinary tract: (number)	Urinary tract: (%)	Respiratory tract: (number)	Respiratory tract: (%)	Other [note 3] : (number)	Other (% [note 3])	Unknown: (number)	Unknown (%)
2017 to 2018	9,823	5,113	52.1%	374	7.3%	1,032	20.2%	1,681	32.9%	470	9.2%	603	11.8%	953	18.6%
2018 to 2019	10,739	5,816	54.2%	493	8.5%	1,105	19.0%	1,943	33.4%	585	10.1%	768	13.2%	922	15.9%
2019 to 2020	11,097	6,110	55.1%	484	7.9%	1,222	20.0%	2,056	33.6%	581	9.5%	745	12.2%	1,022	16.7%
2020 to 2021	11,204	5,496	49.1%	410	7.5%	985	17.9%	1,726	31.4%	710	12.9%	693	12.6%	972	17.7%
2021 to 2022	11,452	5,256	45.9%	367	7.0%	939	17.9%	1,729	32.9%	550	10.5%	745	14.2%	926	17.6%
2022 to 2023	11,865	5,304	44.7%	430	8.1%	875	16.5%	1,809	34.1%	466	8.8%	755	14.2%	969	18.3%
2023 to 2024	13,111	6,078	46.4%	435	7.2%	1,010	16.6%	2,109	34.7%	534	8.8%	791	13.0%	1,199	19.7%
2024 to 2025	13,438	6,095	45.4%	472	7.7%	1,045	17.1%	2,219	36.4%	556	9.1%	698	11.5%	1,105	18.1%

Note 1: financial year from April to March of the following year.

Note 2: gastrointestinal (not hepatobiliary).

Note 3: ‘Other’ includes the following options inputted on the HCAI DCS: bone and joint, central nervous system, genital tract (including prostate), indwelling intravascular device, other, respiratory tract, skin or soft tissue, no clinical signs of bacteraemia.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, for inpatients with a time-to-onset of fewer than 2 days, the most common primary focus of bacteraemia was urinary tract (42.4%) (Table 7). As the time between admission and the onset of bacteraemia increases, the percentage of inpatients reporting the urinary tract as the primary focus decreases from 42.4% for those with onset in less than 2 days to 23.6% (for those with onset in 7 days or more).

Amongst those with a time-to-onset of less than 2 days, 6.5% had a respiratory focus and 5.6% had a gastrointestinal focus. These percentages were higher amongst individuals with a time-to-onset of 7 days or more, at 12.4% and 13.9% for respiratory and gastrointestinal focus respectively. Caution is advised when interpreting these numbers due to low counts and annual fluctuations in trend.

Table 7. Distribution of primary focus of Klebsiella spp. bacteraemia, by time-to-onset, England, by financial year: April 2024 to March 2025

Time to onset (days) [note 1]	Gastrointestinal (not hepatobiliary) (number)	Gastrointestinal (not hepatobiliary) (%) [note 2]	Hepatobiliary (number)	Hepatobiliary (%) [note 2]	Urinary tract (number)	Urinary tract (%) [note 2]	Respiratory tract (number)	Respiratory tract (%) [note 2]	Other (number)	Other (%) [note 2]
Less than 2	122	5.6%	445	20.4%	924	42.4%	141	6.5%	200	9.2%
2 to 6	71	12.5%	94	16.6%	163	28.7%	62	10.9%	75	13.2%
7 and over	198	13.9%	145	10.2%	336	23.6%	177	12.4%	291	20.4%

Note 1: number of days from admission to positive bacteraemia sample (if both are on the same date the difference would be zero days).

Note 2: proportion of cases by primary focus.

Geographic distribution

The crude and age-sex standardised rates are presented across ICBs for FY 2024 to 2025 (Figure 17). Like E. coli (Figure 8) there is high spatial variability in Klebsiella spp. rates. The highest age-sex standardised rates were observed in some London ICBs and followed by South Yorkshire ICB (36.9; 33.5; 33.0; 32.0, 31.3 cases per 100,000 population), while the lowest were observed in Gloucestershire ICB (9.2 cases per 100,000 population), Herefordshire and Worcestershire ICB (16.6 cases per 100,000 population) and Cornwall and the Isles of Scilly ICB (17.0 cases per 100,000 population) (Table S6 in the accompanying data).

Figure 17. Geographic distribution of Klebsiella spp. bacteraemia rate, by Integrated Care Boards, England, by financial year: April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Mortality

In FY 2024 to 2025, 13,438 Klebsiella spp. bacteraemia cases were reported in England (Table S9 in the accompanying data). Information on mortality was available for 98.9% (13,294) of these cases. There were 2,531 deaths within 30 days of a Klebsiella spp. bacteraemia diagnosis, giving a mortality rate of 4.4 deaths per 100,000 population and a CFR of 18.9% (Figure 18).

The mortality rate increased from 3.5 to 4.4 deaths per 100,000 population between FY 2017 to 2018 and FY 2024 to 2025. A steeper increase in mortality rate was also observed between FY 2022 to 2023 and FY 2024 to 2025, increasing by 9.5% from 4.1 to 4.4, coinciding with the steep increase in cases observed for the same period. In contrast, the CFR decreased marginally by 6.2% from 20.1% (1,972 deaths) to 18.9% (2,531 deaths) between FY 2017 to 2018 and FY 2024 to 2025. Mortality rate and CFR increased temporarily at the start of the COVID-19 pandemic in FY 2020 to 2021, reaching 4.3 deaths per 100,000 and 21.7%, predominantly caused by hospital-onset (HO) cases. However, they subsequently returned to levels similar to those seen previously, despite an overall upward trend.

Figure 18. Case-fatality rate and mortality rate of Klebsiella spp. bacteraemia, England: financial year April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Variation by onset of bacteraemia

Between FY 2023 to 2024 and FY 2024 to 2025, the mortality rate of HO cases decreased from 2.7 deaths per 100,000 bed-days (980 deaths) to 2.6 (956 deaths) (Table S11 in the accompanying data). Similarly, CFR for HO cases decreased from 24.7% to 22.9%, with some fluctuations observed in the intervening years.

The mortality rate in community-onset (CO) cases increased from 2.7 deaths per 100,000 population (1,526 deaths) in FY 2023 to 2024 to 2.8 (1,576 deaths) in FY 2024 to 2025. The corresponding CFRs increased from 16.8% to 17.1%.

Variation by age and sex

In FY 2024 to 2025, as in previous years, the mortality rate and CFR increased with age, except amongst those aged one year and under, where values were higher than in the one to 14 years age group (Table S10 in the accompanying data). Overall, the mortality rate was higher in male cases, while the CFR was greater in female cases, except in the 15 to 44 years age group, where female cases had a higher CFR.

For male cases, the highest mortality rate was observed in those aged 85 years and over (79.0 deaths per 100,000 population) and those aged 75 to 84 years (31.5 deaths per 100,000 population) with corresponding CFRs of 26.6% and 20.6% of cases, respectively. Compared with FY 2023 to 2024, mortality rates for male cases aged 85 years and over and aged 75 to 84 years increased by 10.6% and 5.1%, respectively.

For female cases, the highest mortality rate was also observed in those aged 85 years and over (24.2 deaths per 100,000 population) and those aged 75 to 84 years (13.3 deaths per 100,000 population). CFRs for these groups were 27.2% and 22.5%, respectively. Compared to FY 2023 to 2024, mortality rates for female cases aged 85 years and over decreased by 19.8% but increased by 12.5% for those aged 75 to 84 years.

Variation by region

Case-fatality rates in FY 2024 to 2025 were highest in the South East (20.8%) followed by North West (20.6%) and Midlands (19.1%) (Table S12 in the accompanying data). The CFR remained lowest in both London (17.1%) and the South West (17.2%).

Question 5

Epidemiological analysis of Gram-negative organisms: Pseudomonas aeruginosa bacteraemia

Accepted Answer

Total reports

A total of 4,474 cases of Pseudomonas aeruginosa (P. aeruginosa) bacteraemia were reported by NHS acute trusts in England in FY 2024 to 2025 (Table S1 in the accompanying data). Of the 4,474 P. aeruginosa cases, 1,729 (38.6%) were hospital-onset cases. There was little variation in the counts of total P. aeruginosa cases since the start of enhanced surveillance in 2017, except for a spike in the rate of hospital-onset cases in FY 2020 to 2021 (Figure 20). Since then, the rate has declined and remains stable at 4.8 cases per 100,000 bed-days in FY 2024 to 2025.

Figure 19. Trends in the rate of P. aeruginosa bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Hospital and community-onset cases

The rate (cases per 100,000 bed-days) of P. aeruginosa hospital-onset (HO) cases was stable between FY 2017 to 2018 and FY 2019 to 2020, ranging from 4.4 to 4.7 cases per 100,000 bed-days (Figure 19 and Table 8). This increased to 6.1 in FY 2020 to 2021. The observed increase in rate was due to an increase in the reported number of hospital-onset cases, from 1,583 in FY 2019 to 2020 to 1,675 in FY 2020 to 2021, complicated by a decline in bed-days reported due to the COVID-19 pandemic; the hospital-onset rate reverted back in the following financial years, with a rate of 4.8 in FY 2024 to 2025.

Community-onset (CO) cases comprise 61.4% of all reported P. aeruginosa cases in FY 2024 to 2025. In comparison to HO rates, CO rates have remained stable averaging at 4.8 cases per 100,000 population over the 8 surveillance years.

Figure 20. Monthly counts of P. aeruginosa bacteraemia by onset of infection, England, by financial year: April 2017 to March 2025

Table 8. P. aeruginosa bacteraemia counts and rates, England, by financial year: April 2017 to March 2025.

Financial year [note 1]	Mid-year population estimate [note 2]	All reported cases	Rate (all reported cases per 100,000 population)	Total bed-days	Hospital-onset cases	Rate (hospital-onset cases per 100,000 bed-days)	Community-onset cases	Rate (community-onset cases per 100,000 population)
2017 to 2018	55,694,748	4,315	7.7	34,903,075	1,628	4.7	2,687	4.8
2018 to 2019	55,999,864	4,191	7.5	34,538,184	1,521	4.4	2,670	4.8
2019 to 2020	56,369,653	4,350	7.7	34,637,156	1,583	4.6	2,767	4.9
2020 to 2021	56,266,460	4,301	7.6	27,628,155	1,675	6.1	2,626	4.7
2021 to 2022	56,692,394	4,346	7.7	32,905,086	1,631	5.0	2,715	4.8
2022 to 2023	57,112,542	4,418	7.7	35,490,766	1,701	4.8	2,717	4.8
2023 to 2024	57,230,111	4,457	7.8	35,991,392	1,714	4.8	2,743	4.8
2024 to 2025	56,994,974	4,474	7.8	36,195,302	1,729	4.8	2,745	4.8

Note 1: financial year ranges from April of one year to March of the following year.

Note 2: ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Seasonal trends

Seasonality was assessed as the number of cases each quarter as a percentage of total cases for the financial year. This analysis was performed separately for hospital-onset and community-onset cases. When assessing the distribution of community-onset P. aeruginosa cases per financial year, the greatest proportion of cases occur in the July to September quarter of each financial year (Table S7 in the accompanying data). This has been observed since the beginning of P. aeruginosa surveillance in FY 2017 to 2018, where on average 28.4% of community-onset cases in the financial year occur in the summer quarter. Since FY 2017 to 2018 on average (except for FY 2020 to 2021) 27.2% of hospital-onset cases in the financial year occur in the summer quarter.

Prior trust exposure

There was an increase of 3.2% in the number of hospital-onset healthcare-associated (HOHA) P. aeruginosa cases in FY 2024 to 2025, compared to FY 2020 to 2021, rising from 1,675 to 1,729, with a 21.2% drop in the incidence rate of HOHA, from 6.1 to 4.8 cases per 100,000 bed-days. Over the same period, the number of community-onset healthcare-associated (COHA) cases increased by 3.7% from 753 to 781 cases, with a drop in the rate to 1.9 cases per 100,000 bed-days and day admissions in FY 2024 to 2025. Community-onset community-associated (COCA) cases increased by 6.6% from 1,842 to 1,964 and 5.3% from 3.3 to 3.4 cases per 100,000 population, respectively (Table S8 in the accompanying data).

Since FY 2020 to 2021 the distribution of cases by prior trust distribution has remained stable. In FY 2024 to 2025 43.9% of cases were COCA, 17.5% COHA and 38.6% HOHA (Figure 21).

These comparisons should be interpreted with caution as FY 2019 to 2020 had 430 cases without prior trust exposure data, which became mandatory in late 2019, and therefore may underestimate the proportion of COHA and COCA cases, compared with zero missing information cases in subsequent years.

Figure 21. Proportion of prior trust exposure of P. aeruginosa bacteraemia cases, England, by financial year, April 2020 to March 2025

Age and sex distribution

Overall, there was not much difference in the age and sex distribution of P. aeruginosa cases as a percentage of all reported cases in FY 2017 to 2018 and FY 2024 to 2025 (Figure 22 and Table S2 in the accompanying data). Most cases occurred in male cases aged 45 years and over. The highest proportion of cases for male and female cases in FY 2024 to 2025 occurred amongst those aged 75 to 84 years (also top in 45 to 64 year old females), accounting for 18.6% and 8.3% of total cases, respectively. Additionally, female cases were also notably high in those aged 45 to 64 years also accounting for 8.3%. Similar to Klebsiella spp., in FY 2024 to 2025, the percentage of male cases amongst those aged 15 to 44 years was like female cases. This was not the case for E. coli bacteraemia, for which female cases were substantially higher.

Figure 22. Age and sex distribution of P. aeruginosa bacteraemia by percentage of cases, England, by financial years April 2017 to March 2018 and April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, except for those aged one year and under, the incidence rate of P. aeruginosa bacteraemia increased with age for both male and female cases; the highest rate observed was amongst those aged 85 years and over. The rate in male cases aged 85 years and over between FY 2017 to 2018 to FY 2024 to 2025 increased by 2.8% (from 111.3 cases to 114.4 cases per 100,000 population). Over the same period, the rate in female cases aged 85 years and over decreased by 15.9% from 34.6 to 29.1 cases per 100,000 population (Figure 23), further widening the gap between the sexes.

Those aged one year and under are a relatively high-risk group. Of note, between FY 2017 to 2018 and FY 2024 to 2025, the rate for female cases in this age group increased, while male cases displayed a slight decrease. For female cases this increased by 38.6% from 6.7 to 9.3. For male cases, there was a 5.1% decrease from 9.7 to 9.2. All other age groups remained comparable between the 2 financial years.

Trends in the age-specific and sex-specific rates of P. aeruginosa bacteraemia are shown in Figure 23. The rates are higher in male cases compared with female cases, especially in the older age groups (aged 65 years and over). Since FY 2017 to 2018, the incidence rate in male cases aged 85 and older has fluctuated between 91.3 and 114.4 cases per 100,000 population. In FY 2024 to 2025, there was a rise in the incidence rate amongst male cases aged 85 years and over, a 5.2% increase (from 108.7 to 114.4 cases per 100,000 population) from the last financial year (FY 2023 to 2024). For male cases aged 75 to 84 years, there was an 8.2% decrease from 53.5 to 49.1, for the same period.

The rate of incidence for female cases aged 85 years and over was 29.1 for FY 2024 to 2025, a 12.2% increase since FY 2023 to 2024.

Generally, all other age groups, for both male and female cases, have remained broadly stable over the 7 years since the start of P. aeruginosa bacteraemia mandatory surveillance. The exception to this for both male and female cases was in those aged one year and under. Caution is advisable when interpreting data for P. aeruginosa amongst those aged 14 years and under as the number of cases is too small to properly interpret trends.

Cases in which the age and or sex was missing or reported as ‘unknown’ were excluded. In both FY 2017 to 2018 and FY 2024 to 2025, zero cases had an ‘unknown’ age or sex.

Figure 23. Trends in age group and sex rates of P. aeruginosa bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by ethnicity

In FY 2024 to 2025, the observed incidence rate of P. aeruginosa bacteraemia was highest in the Black and White ethnic groups (8.2 and 8.0 cases per 100,000 population, respectively) (Figure 24 and Table S14 in the accompanying data). It was intermediate in the Asian ethnic group (5.4 cases per 100,000 population), and lowest in the Mixed and Other ethnic groups (2.4 and 2.2 cases per 100,000 population, respectively).

Age-standardised incidence rates are much greater than observed incidence in all except the White ethnic group. The Black ethnic group sees the highest incidence compared with the other ethnic groups consistently over the surveillance period. However, recent years have seen a plateau at 13.0 cases per 100,000 population. The Asian ethnic group has seen an increasing trend since April 2017, while the White ethnic group has remained relatively constant at 7.3 cases per 100,000 population. The Other ethnic group has fluctuated in the past 8 years without trend.

Figure 24. P. aeruginosa bacteraemia rate by ethnicity, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Trends by deprivation

Unlike the other reported organisms, in FY 2024 to 2025, the observed incidence rate for P. aeruginosa bacteraemia did not substantially differ by deprivation, ranging from 7.4 to 8.1 cases per 100,000 population (Figure 25 and Table S13 in the accompanying data).

However, age-sex standardised incidence rates of P. aeruginosa bacteraemia varied more widely by deprivation with larger or smaller rates than observed, with 9.6 and 6.5 cases per 100,000 population in the 20% most or 20% least deprived areas, respectively. Since April 2017, all levels have fluctuated without apparent trend.

Figure 25. P. aeruginosa bacteraemia rate by deprivation, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Primary focus of P. aeruginosa bacteraemia

Reporting of primary focus for P. aeruginosa remains low. In FY 2024 to 2025, the primary focus was reported for 46.9% of cases, a decrease from 49.3% from the start of surveillance in FY 2017 to 2018 (Table S4 in the accompanying data).

The most frequent primary focus of P. aeruginosa bacteraemia was the urinary tract, constituting 31.1% of cases in FY 2024 to 2025. Over the 8 financial years from April 2017 to March 2025, the percentage of primary focus reported as the urinary tract was similar (range: 28.8% to 31.1%) and was the most reported primary focus of bacteraemia (Table 9). As observed with Klebsiella spp., in the 3 financial years between April 2017 and March 2020 the percentage of cases reporting respiratory tract as a primary focus remained stable (range:13.0% to 14.1%). However, in FY 2020 to 2021, there was an increase in the percentage of primary focus reported as the respiratory tract to 16.1% which coincided with the first 2 waves of the COVID-19 pandemic. This reduced to 15.1% in FY 2021 to 2022 and then further declined to 12.4% by FY 2023 to 2024. In FY 2024 to 2025, the percentage increased to 13.5%, but this was in line with pre-pandemic levels.

Table 9. P. aeruginosa bacteraemia counts and percentages by primary focus of bacteraemia, England, by financial year: April 2017 to March 2025

Financial year [note 1]	Total P. aeruginosa reported	Primary focus ascertained: (number)	Primary focus ascertained: (%)	Gastro-intestinal: (number) [note 2]	Gastro-intestinal: (%) [note 2]	Hepatobiliary: (number)	Hepatobiliary: (%)	Urinary tract: (number)	Urinary tract: (%)	Respiratory tract: (number)	Respiratory tract: (%)	Other: (number) [note 3]	Other: (%) [note 3]	Unknown: (number)	Unknown: (%)
2017 to 2018	4,315	2,129	49.3%	126	5.9%	102	4.8%	638	30.0%	300	14.1%	491	23.1%	472	22.2%
2018 to 2019	4,191	2,161	51.6%	155	7.2%	100	4.6%	644	29.8%	281	13.0%	558	25.8%	423	19.6%
2019 to 2020	4,350	2,320	53.3%	160	6.9%	123	5.3%	716	30.9%	313	13.5%	549	23.7%	459	19.8%
2020 to 2021	4,301	2,118	49.2%	129	6.1%	116	5.5%	612	28.9%	341	16.1%	503	23.7%	417	19.7%
2021 to 2022	4,346	1,933	44.5%	117	6.1%	94	4.9%	600	31.0%	291	15.1%	461	23.8%	370	19.1%
2022 to 2023	4,418	1,915	43.3%	147	7.7%	96	5.0%	551	28.8%	268	14.0%	453	23.7%	400	20.9%
2023 to 2024	4,457	2,022	45.4%	148	7.3%	111	5.5%	593	29.3%	250	12.4%	503	24.9%	417	20.6%
2024 to 2025	4,474	2,099	46.9%	156	7.4%	118	5.6%	653	31.1%	284	13.5%	476	22.7%	412	19.6%

Note 1: financial year from April to March of the following year.

Note 2: gastrointestinal (not hepatobiliary).

Note 3: ‘Other’ includes the following options inputted on the HCAI DCS: bone and joint, central nervous system, genital tract (including prostate), indwelling intravascular device, other, respiratory tract, skin or soft tissue, no clinical signs of bacteraemia.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

In FY 2024 to 2025, for inpatients with a time-to-onset (days between hospital admission and specimen date) of fewer than 2 days, the most common primary focus of bacteraemia was the urinary tract (36.3%) (Table 10). As time between admission and positive specimen increased, the percentage of inpatients reporting primary focus as the urinary tract decreased to 22.5% amongst those with a time-to-onset of 7 days or greater.

In contrast, as the number of days between admission and positive specimen increased, so did the percentage of individuals with a reported respiratory tract primary focus from 10.3% amongst those with fewer than 2 days, peaking at 16.3% in the 2 to 6 days group before declining to 14.1% amongst those with 7 days or greater. Similarly, gastrointestinal (not hepatobiliary) increased from 6.6% amongst those with less than 2 days to 12.1% in the 2 to 6 days group followed by a decrease to 9.4% amongst those with 7 days or greater.

Table 10. Distribution of primary focus of P. aeruginosa bacteraemia, by time-to-onset, England, by financial year: April 2024 to March 2025

Time to onset (days) [note 1]	Gastrointestinal (not hepatobiliary) (number)	Gastrointestinal (not hepatobiliary) (%) [note 2]	Hepatobiliary (number)	Hepatobiliary (%) [note 2]	Urinary tract (number)	Urinary tract (%) [note 2]	Respiratory tract (number)	Respiratory tract (%) [note 2]	Other (number)	Other (%) [note 2]
Less than 2	41	6.6%	36	5.8%	225	36.3%	64	10.3%	119	19.2%
2 to 6	23	12.1%	21	11.1%	40	21.1%	31	16.3%	44	23.2%
7 and over	63	9.4%	43	6.4%	151	22.5%	95	14.1%	195	29.0%

Note 1: number of days from admission to positive bacteraemia sample (if both are on the same date the difference would be zero days).

Note 2: proportion of cases by primary focus.

Geographic distribution

The crude and age-sex standardised rates is presented across ICBs for FY 2024 to 2025. There was clustering of high incidence rates of P. aeruginosa in London while moderate rates are clustered across the country. Areas across the South West, North West and around Bristol typically had lower rates (Figure 26). The highest age-sex standardised incidence rate was observed in some London ICBs and Coventry and Warwickshire ICBs (14.2, 11.2, 11.0, 10.6 and 10.0 cases per 100,000 population), while the lowest were observed in Gloucestershire ICB (2.6 cases per 100,000 population), Devon ICB (4.4 cases per 100,000 population) and Lancashire and South Cumbria ICB (4.9 cases per 100,000 population) (Table S6 in the accompanying data).

Figure 26. Geographic distribution of P. aeruginosa bacteraemia rate, by Integrated Care Boards, England, by financial year: April 2024 to March 2025

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Mortality

In FY 2024 to 2025, 4,474 P. aeruginosa bacteraemia cases were reported in England (Table S9 in the accompanying data). Information on mortality was available for 98.9% (4,426) of these cases. There were 1,100 deaths within 30 days of a P. aeruginosa bacteraemia, with a mortality rate of 1.9 deaths per 100,000 population and a CFR of 24.7% (Figure 27).

The mortality rate has remained consistent at around 1.9 deaths per 100,000 population between FY 2021 to 2022 and FY 2024 to 2025. The CFR had decreased from 27.0% (1,161 deaths) in FY 2017 to 2018 to 24.7% (1,100 deaths) in FY 2024 to 2025.

Figure 27. Case-fatality rate and mortality rate of P. aeruginosa bacteraemia, England, by financial year: April 2017 to March 2025

Note: shaded bands indicate 95% CIs.

ONS mid-year population estimates for calendar years 2023 to 2025 inclusive were unavailable at time of publication and so population data for calendar year 2022 was used as a proxy.

Variation by onset of bacteraemia

Between FY 2018 to 2019 and FY 2024 to 2025, the CFR of hospital-onset (HO) cases increased slightly from 27.2% to 28.0%, while for community-onset (CO) cases over the same period the CFR had minor fluctuations but declined marginally from 22.7% to 22.6% (Table S11 in the accompanying data). Compared with FY 2023 to 2024, CFR in HO cases in FY 2024 to 2025 decreased marginally from 28.4% to 28.0%, while CO cases increased slightly from 22.5% to 22.6%.

In FY 2024 to 2025, the mortality rate of HO cases remained stable at 1.3 deaths per 100,000 bed-days when compared the previous FY 2023 to 2024 (483 and 485 deaths, respectively). Over the same period, the mortality rate in CO cases remained stable at 1.1 deaths per 100,000 population (618 deaths and 616 deaths, respectively).

Variation by age and sex

In FY 2024 to 2025, CFR and mortality rate generally increased with age, except amongst children aged one year and under, which was higher than those aged one to 14 years (Table S10 in the accompanying data). The mortality rate was greater in male cases (except those aged 15 to 44 years) while the CFR was greater in female cases except those aged under one year.

In FY 2024 to 2025, the highest mortality rates in male cases were in those aged 85 years and over (31.8 deaths per 100,000 population) and those aged 75 to 84 years (12.0 deaths per 100,000 population), which corresponded to CFRs of 27.9% and 24.4% of cases, respectively.

In female cases of the same age groups, the mortality rates were far lower than their male counterparts; 10.0 deaths per 100,000 population (aged 85 years and over) and 6.5 deaths per 100,000 population (aged 75 to 84 years). However, these equated to higher CFRs than male cases of 34.4% and 35.4% of all cases in these age groups.

Amongst children aged one year and under, the mortality rate in male cases was 3.9 deaths per 100,000 population and 3.4 in female cases. As the number of deaths was relatively small in both male and female cases, caution is required in interpreting this data.

Variation by region

Case-fatality rates in FY 2024 to 2025 were highest in the North West (30.3%) followed by South East (26.1%) and the East of England (26.1%). The CFR remained lowest in London at 21.2% and South West (22.2%) (Table S12 in the accompanying data).

Question 6

E. coli, Klebsiella spp. and P. aeruginosa discussion and comparison

Accepted Answer