Official Statistics

National norovirus and rotavirus report, week 39 report: data to week 38 (data up to 21 September 2025)

Updated 25 September 2025

Applies to England

This monthly report covers the 4-week period between 25 August 2025 and 21 September 2025. Data reported here provides a summary of norovirus and rotavirus activity in England in the 2025/2026 season up to reporting week 38 of 2025.

In this report the ‘5-season average’ is calculated from the same period during the 5 seasons of 2017/2018, 2018/2019, 2022/2023, 2023/2024 and 2024/2025. Please see Data sources and methodology for more information and for guidance on interpretation of trends.

Main points

The main messages of this report are:

• norovirus and rotavirus activity has remained low and was within expected levels during this reporting period

• total norovirus laboratory reports between weeks 35 and 38 of 2025 were 16.5% lower than the 5-season average for the same 4-week period

• total rotavirus laboratory reports between weeks 35 and 38 of 2025 were 11.1% higher than the 5-season average for the same 4-week period

• the number of norovirus outbreaks reported to the Hospital Norovirus Outbreak Reporting System (HNORS) since the start of the 2025/2026 season is 69.7% lower than the 5-season average

• during the 2025/2026 season to date, the majority (84.0%) of samples characterised were norovirus genogroup 2 (GII), of which the most frequent genotypes identified were GII.4 (26.8%) and GII.17 (26.8%)

Laboratory surveillance

Data presented here is derived from the Second Generation Surveillance System (SGSS). Please see Data sources and methodology for more information and for guidance on interpretation of trends.

Norovirus

Overall, up to week 38 of 2025 season the cumulative number of positive norovirus laboratory reports in England (896 laboratory reports) was comparable to the 5-season average (1.5% lower) for the same period (910 laboratory reports).

Norovirus activity has remained low in recent weeks. Total norovirus laboratory reports between weeks 35 and 38 of 2025 (233 laboratory reports) were 16.5% lower than the 5-season average (279 laboratory reports) for the same 4-week period (Figure 1). Overall, norovirus laboratory reports between weeks 35 and 38 were 24.4% lower than during the previous 4-week period of weeks 31 to 34 of 2025 (308 laboratory reports).

Figure 1. Weekly norovirus laboratory reports in England during the 2025/2026 season, compared with the 5-season average

Note 1: the grey shading represents 95% confidence intervals for the 5-season average.

Data behind this graph can be found in the accompanying spreadsheet.

Figures 2 and 3 show the trends in the rate of norovirus-positive laboratory reports per 100,000 people each week, by age group (Figure 2) and region of England (Figure 3). During this reporting period, the rate remained low across all regions and age groups but was highest among individuals aged 0 to 4 years (Figure 2).

Figure 2. Norovirus laboratory reports per 100,000 people by week and age group in England during the 2025/2026 season

Note 2: the range of the y-axis has been set based on the expected seasonal range from historical data.

Data behind this graph can be found in the accompanying spreadsheet.

Figure 3. Norovirus laboratory reports per 100,000 people by week and region in England during the 2025/2026 season

Note 3: regional data is presented by region of the reporting laboratory. The range of the y-axis has been set based on the expected seasonal range from historical data.

Data behind this graph can be found in the accompanying spreadsheet.

Rotavirus

The cumulative number of positive rotavirus laboratory reports in England up to week 38 of 2025 (517 laboratory reports) was comparable to the 5-season average (0.8% lower) for the same period (521 laboratory reports) (Figure 4).

Figure 4. Weekly rotavirus laboratory reports in England during the 2025/2026 season, compared with the 5-season average

Note 1: the grey shading represents 95% confidence intervals for the 5-season average.

Data behind this graph can be found in the accompanying spreadsheet.

Rotavirus activity has remained within expected levels in recent weeks. The total number of positive rotavirus laboratory reports (134 laboratory reports) for the 4-week period of weeks 35 to 38 of 2025 was 11.1% higher than the 5-season average (121 laboratory reports) for the same period. Total rotavirus laboratory reports during this period were 10.1% lower than the previous 4-week period of weeks 31 to 34 of 2025 (149 laboratory reports).

Outbreak surveillance

Data presented here is derived from the Hospital Norovirus Outbreak Reporting System (HNORS). Please see Data sources and methodology for more information and for guidance on interpretation of trends.

Outbreaks in hospital settings

Up to week 38 of the 2025/2026 season, 6 outbreaks have been reported to HNORS (Figure 5), 69.7% lower than the 5-season average for the same period (20 outbreaks). Overall, 83.3% of outbreaks were laboratory confirmed as norovirus.

Figure 5. Suspected and confirmed norovirus outbreaks reported to HNORS by week of occurrence in England during the 2025/2026 season, compared with the 5-season average

Data behind this graph can be found in the accompanying spreadsheet.

During the 4-week period of weeks 35 to 38 of 2025, reported outbreaks (1 outbreak) were 85.7% lower than to the 5-season average for the same period (7 outbreaks).

During the 5 seasons from which the 5-season average was calculated, overall, 88.6% of outbreaks reported to HNORS were laboratory confirmed as norovirus.

Molecular surveillance for norovirus

Data presented here is provided by UKHSA’s Enteric Virus Unit (EVU) and is used by UKHSA to monitor circulating norovirus variants. Please see Data sources and methodology for more information and for guidance on interpretation of trends.

Of the 257 norovirus positive samples characterised during the 2025/2026 season to date, 84.0% were genogroup 2 (GII); 15.6% were genogroup 1 (GI); and 0.4% were mixed (Table 1).

Table 1. Norovirus-positive samples by genogroup, England, 2025/2026 to date

Genogroup	Number of sequences	Percentage of total (%)
Genogroup 2 (GII)	216	84.0%
Genogroup 1 (GI)	40	15.6%
Mixed	1	0.4%
Total	257	100.0%

Note 4: percentages may not sum to 100% because of rounding.

The most frequent norovirus GII genotypes identified were GII.4 (26.8%) and GII.17 (26.8%). The most frequent norovirus GI genotype identified was GI.3 (6.6%) (Table 2).

Table 2. Norovirus-positive samples by genotype, England, 2025/2026 to date

Genotype	Number of sequences	Percentage of total (%)
GII.4	69	26.8%
GII.17	69	26.8%
GII.3	23	8.9%
GII other	55	21.4%
GI.3	17	6.6%
GI other	23	8.9%
Mixed	1	0.4%
Total	257	100.0%

Note 4: percentages may not sum to 100% because of rounding.

In April 2024, GII.17 emerged and a trend for increasing detections of GII.17 was noted in the United States and other European countries (1). During the 2024/2025 season, GII.17 was the most commonly detected norovirus genotype. However, since early 2025 detections of GII.4 have been increasing and by the end of the 2024/2025 season GII.4 was the most commonly detected genotype.

Data sources and methodology

No single surveillance system fully captures national changes in norovirus or rotavirus activity. This report presents data from 3 systems and even though when combined they do not capture norovirus or rotavirus activity fully, they do collectively describe recent trends.

The Second Generation Surveillance System (SGSS) is the national laboratory reporting system, recording positive laboratory reports of norovirus and rotavirus.

The Hospital Norovirus Outbreak Reporting System (HNORS) is a web-based scheme for reporting suspected and confirmed norovirus outbreaks in acute NHS trust hospitals, and captures information on the disruptive impact these outbreaks have in hospital settings.

Norovirus characterisation data is produced by the Enteric Virus Unit (EVU) and is used to monitor the diversity of circulating strains of norovirus in England.

Data used to produce the statistics is typically extracted on a Monday, including any records reported by the previous Sunday, and the report is then published on the Thursday of that week. However, in the event of a bank holiday this cadence may change.

Under-ascertainment is a recognised challenge in enteric virus surveillance with sampling, testing and reporting criteria known to vary by region. All surveillance data included in this report is extracted from live reporting systems, is subject to a reporting delay, and the number reported in the most recent weeks may rise further as more reports are received.

Data is reported by the norovirus and rotavirus season rather than calendar year. To capture the winter peak of activity within one reporting period, the norovirus and rotavirus season runs from week 27 in year 1 to week 26 in year 2, currently week 27 2025 to week 26 2026 (July to June). The 2025/2026 season is compared to the 5-season average calculated from the 5 seasons of 2017/2018, 2018/2019, 2022/2023, 2023/2024 and 2024/2025. The 2019/2020, 2020/2021 and 2021/2022 seasons are not included in this calculation due to the adverse impact of the emergence of COVID-19 on surveillance part way through the 2019/2020 season and the continued impact into the 2020/2021 and 2021/2022 seasons.

Please see the quality and methodology information report for more information on data sources, methodology, interpretation of trends and impact of COVID-19 pandemic on surveillance.

Background information

Norovirus activity and the timing of the peak in reporting can vary considerably and differ from one season to the next. Transmission is mostly via contact with an infected person, but norovirus can also be spread by consumption of food contaminated with the virus or contact with contaminated surfaces. Norovirus transmission is influenced by many factors including, but not limited to, whether the person has been infected with norovirus recently, community contact patterns and the time of the year, as infections peak in the colder months and therefore norovirus is most prevalent during winter.

Since the 2019/2020 season, norovirus activity in England has been more variable compared to historical trends, likely due to multiple impacts of the COVID-19 pandemic. Throughout the 2019/2020 and 2020/2021 seasons a reduction in reporting to national surveillance was observed, followed by unusual activity in the 2021/2022 season such as a greater proportion of outbreaks reported in educational settings than prior to the pandemic. In the 2022/2023 season norovirus activity returned to pre-pandemic levels and in early 2023 norovirus reporting peaked at a level twice as high as that experienced in the decade prior to the emergence of COVID-19, as predicted by modelling undertaken in 2021 (2).

Following the introduction of the rotavirus vaccine in July 2013 the total number of laboratory-confirmed rotavirus infections each season has remained low compared to the pre-vaccine period. A 77% decrease in laboratory-confirmed rotavirus infections in infants was observed in the first season following vaccine introduction (3).

Reporting of enteric virus outbreak surveillance data from HPZone in the national norovirus and rotavirus report was paused in August 2024 due to quality assurance concerns related to the migration of outbreak surveillance data from HPZone to the Case and Incident Management System (CIMS). In August 2025, the UKHSA norovirus and rotavirus surveillance team determined that due to differences in how the data is captured between the systems it was not appropriate to include CIMS data in the report. The team will continue to review outbreak surveillance data internally and explore options for sharing it with stakeholders where appropriate.

UKHSA routinely undertakes norovirus characterisation as part of national surveillance to monitor the diversity of circulating strains. This molecular surveillance enables detection of novel strains or emergence of existing strains that could lead to a strain replacement event. In England, previous norovirus strain replacement events have been associated with both a temporal shift in the peak of activity when GII.4/Sydney/2012 emerged during the 2012/2013 season (4) and an overall increase in norovirus activity when the GII.17 genotype dominated during the 2024/2025 season (5), both of which placed unexpected pressure on the health and social care sectors.

Worldwide, the most commonly detected norovirus genotype is genogroup II- genotype 4 (GII.4). Between 1995 and 2013 there were 5 global GII.4 strain replacements events (6, 7). Since the winter of the 2012/2013 season and prior to the emergence of COVID-19 in England the most frequently detected strain was Norovirus/GII.4/Sydney/2012 or GII.4 Sydney2012-like variants (8), until April 2024 when GII.17 emerged (1)

To enable effective molecular surveillance, it is crucial that samples are obtained from suspected norovirus cases or outbreaks for laboratory confirmation and then norovirus-positive samples are referred on to the EVU for characterisation.

Further information and contact details

Further information about norovirus surveillance and rotavirus surveillance is available on GOV.UK.

Feedback and contact information

This report was produced by the Gastrointestinal Infections, Food Safety and One Health Division, UKHSA.

Please direct any queries or comments to NoroOBK@ukhsa.gov.uk

Alternatively, you can contact OSR by emailing regulation@statistics.gov.uk or via the OSR website.

References

1. Chhabra and others. ‘Increased circulation of GII.17 noroviruses, six European countries and the United States, 2023 to 2024’ EuroSurveillance: volume 29, pages 1 to 6 (viewed on 26 September 2024)

2. O’Reilly and others. ‘Predicted norovirus resurgence in 2021-2022 due to the relaxation of nonpharmaceutical interventions associated with COVID-19 restrictions in England: a mathematical modeling study’ BMC Medicine: volume 19, article number 299 (viewed on 22 September 2025

3. Atchison and others. ‘Rapid declines in age group–specific rotavirus infection and acute gastroenteritis among vaccinated and unvaccinated individuals within 1 year of rotavirus vaccine introduction in England and Wales’ The Journal of Infectious Diseases: volume 213, pages 243 to 249 (viewed on 17 October 2022)

4. Allen and others. ‘Emergence of the GII-4 norovirus Sydney2012 strain in England, winter 2012–2013’ The Public Library of Science One: volume 2, article e88978 (viewed on 17 October 2022)

5. UKHSA. ‘National norovirus and rotavirus report, week 28 report: data to week 26 (data up to 29 June 2025)’ (viewed on 22 September 2025)

6. Allen and others. ‘Characterisation of a GII-4 norovirus variant-specific surface-exposed site involved in antibody binding’ Virology Journal: volume 6, article number 150 (viewed on 17 October 2022)

7. Zakikhany and others. ‘Molecular evolution of GII-4 Norovirus strains’ The Public Library of Science One: volume 7, article e41625 (viewed on 17 October 2022)

8. Ruis C and others. ‘The emerging GII.P16-GII.4 Sydney 2012 norovirus lineage is circulating worldwide, arose by late-2014 and contains polymerase changes that may increase virus transmission’ The Public Library of Science One: volume 6, article e0179572 (viewed on 17 October 2022)

Acknowledgements

We are grateful to all who provided data used in this report, including NHS Infection Control and Prevention staff (HNORS users), UKHSA local health protection teams (HPTs), UKHSA regional teams (Field Services) and UKHSA Regional Public Health and collaborating laboratories.

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