National norovirus and rotavirus report, week 35 report: data to week 34 (data up to 24 August 2025)
Updated 28 August 2025
Applies to England
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This publication is available at https://www.gov.uk/government/statistics/national-norovirus-and-rotavirus-surveillance-reports-2025-to-2026-season/national-norovirus-and-rotavirus-report-week-35-report-data-to-week-34-data-up-to-24-august-2025
This monthly report covers the 4-week period between 28 July 2025 and 24 August 2025. Data reported here provides a summary of norovirus and rotavirus activity in England up to reporting week 34 of the 2025/2026 season.
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.
As of the report published in week 31 2025, this report now includes data up to the Sunday 4 days prior to publication, rather than the Sunday 11 days prior (as previously) in order to ensure timely release of information. Due to a reporting delay, figures for the most recent week prior to publication are likely to increase in subsequent reports as more samples become available. This change in the methodology will be explained further in an upcoming quality and methodology information report.
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 31 and 34 of 2025 was comparable to the 5-season average for the same 4-week period
- total rotavirus laboratory reports between weeks 31 and 34 of 2025 were 12.3% lower 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 62.1% lower than the 5-season average
- during the 2025/2026 season to date, the majority (83.2%) of samples characterised were norovirus genogroup 2 (GII), of which the most frequent genotype identified was GII.4 (29.2%)
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 34 of the 2025/2026 season the cumulative number of positive norovirus laboratory reports in England (645 laboratory reports) was comparable to the 5-season average (2.2% higher) for the same period (631 laboratory reports).
Total norovirus laboratory reports during weeks 31 and 34 of 2025 (290 laboratory reports) were comparable to the 5-season average (0.3% higher) for the same 4-week period (289 laboratory reports) (Figure 1). Overall, norovirus laboratory reports between weeks 31 and 34 were 18.3% lower than during the previous 4-week period of weeks 27 and 30 of 2025 (355 laboratory reports).
Figure 1. Weekly norovirus laboratory reports in England during the 2025/2026 season, compared with the 5-season average
Note: the grey shading represents 95% confidence intervals for the 5-season average. Data 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).
Figure 2. Norovirus laboratory reports per 100,000 people by week and age group in England during the 2025/2026 season
Note: The range of the y-axis has been set based on the expected seasonal range from historical data. Data 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: 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 can be found in the accompanying spreadsheet.
Rotavirus
The cumulative number of positive rotavirus laboratory reports in England up to week 34 of the current season (365 laboratory reports) was 8.9% lower than the 5-season average for the same period (401 laboratory reports) (Figure 4).
Figure 4. Weekly rotavirus laboratory reports in England during the 2025/2026 season, compared with the 5-season average
Note: the grey shading represents 95% confidence intervals for the 5-season average. Data can be found in the accompanying spreadsheet.
Rotavirus activity has decreased in recent weeks. The total number of laboratory reports (134 laboratory reports) for the 4-week period of weeks 31 and 34 of 2025 were 12.3% lower than the 5-season average (153 laboratory reports) for the same period. Total rotavirus laboratory reports during this period were 42.0% lower than the previous 4-week period of weeks 27 and 30 of 2025 (231 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 34 of the 2025/2026 season, 5 outbreaks have been reported to HNORS (Figure 5), 62.1% lower than the 5-season average for the same period (13 outbreaks). Overall, 80.0% 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
Note: data can be found in the accompanying spreadsheet.
During the 4-week period of weeks 31 and 34 of 2025, reported outbreaks (1 outbreak) were 80.0% lower than to the 5-season average for the same period (5 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 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 185 norovirus positive samples characterised during the 2025/2026 season to date, 83.2% were genogroup 2 (GII); 16.2% were genogroup 1 (GI); and 0.5% 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) | 154 | 83.2% |
| Genogroup 1 (GI) | 30 | 16.2% |
| Mixed | 1 | 0.5% |
| Total | 185 | 100.0% |
Note: percentages may not sum to 100% because of rounding.
The most frequent norovirus GII genotype identified was GII.4 (29.2%) and the second most frequent genotype identified was GII.17 (25.9%). The most frequent norovirus GI genotype identified was GI.3 (8.1%) (Table 2).
Table 2. Norovirus-positive samples by genotype, England, 2025/2026 to date
| Genotype | Number of sequences | Percentage of total (%) |
|---|---|---|
| GII.4 | 54 | 29.2% |
| GII.17 | 48 | 25.9% |
| GII other | 52 | 28.1% |
| GI.3 | 15 | 8.1% |
| GI other | 15 | 8.1% |
| Mixed | 1 | 0.5% |
| Total | 185 | 100.0% |
Note: 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
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 EVU and is used to monitor the diversity of circulating strains of norovirus in England.
Data used to produce the statistics is usually 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 will change.
Background information
No single surveillance system fully captures national changes in norovirus or rotavirus activity. This report presents data from 4 systems and even though when combined they do not capture norovirus or rotavirus activity fully, they do collectively describe recent trends. Data is reported by season rather than calendar year, in order to capture the winter peak of activity in one reporting period. Please see Data sources and methodology for more information and for guidance on interpretation of trends.
Norovirus activity and the timing of the peak in reporting can vary considerably and differ from 1 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. Please see Data sources and methodology and Impact of COVID-19 pandemic on surveillance for more information on the impact of the 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.
On 6 April 2025 norovirus became a notifiable causative agent in schedule 2 of Health Protection (Notification) (Amendment) Regulations 2025. After this date all diagnostic laboratories in England which test human samples for norovirus are legally required to report any positive norovirus test result to the UK Health Security Agency (UKHSA) within 7 days of the result becoming available. It is likely that this change has resulted in more timely notification of positive norovirus laboratory reports to UKHSA.
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 (2).
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 and which have previously been associated with a temporal shift in norovirus activity (3). Norovirus activity varies from season to season and therefore differences will be observed between every season.
Worldwide, the most commonly detected norovirus genotype is genogroup II- genotype 4 (GII.4). Historically between 1995 and 2013 there have been 5 global GII.4 strain replacements events (4, 5). 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 (6), 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 Enteric Virus Unit (EVU) for characterisation.
Interpretation of trends
In order to capture the winter peak of activity in the reporting period the norovirus and rotavirus season runs from week 27 in year 1 to week 26 in year 2, that is, 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 2021/22 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. In years with a week 53 (2015 and 2020) data is combined with week 52 data to avoid distortion of the figure.
Under-ascertainment is a recognised challenge in enteric virus surveillance with sampling, testing and reporting criteria known to vary by region. In addition, samples for microbiological confirmation are collected in a small proportion of community outbreaks. Therefore, this report provides an overview of enteric virus activity across England and data should be interpreted with caution.
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.
Impact of COVID-19 pandemic on surveillance
UKHSA relaunched the Official Statistics ‘National norovirus and rotavirus report’ after it was temporarily suspended due to quality issues with the data from the 4 data sources mentioned above during the COVID-19 pandemic period. Additional analyses of this data were undertaken and demonstrated the quality of this data was comparable with the data collected before the pandemic and therefore reporting was allowed to resume as an Official Statistic. Between December 2020 and October 2022 the report was replaced by the ‘National norovirus and rotavirus bulletin’ to ensure an overview of norovirus and rotavirus activity in England continued to be available to the public.
Data covering the periods 2020/2021 and 2021/2022 is available at National norovirus and rotavirus bulletins 2020 to 2021: management information and National norovirus and rotavirus bulletins 2021 to 2022: management information).
The coronavirus (COVID-19) pandemic impacted activity across many gastrointestinal pathogen surveillance indicators for England in 2020 and 2021, and reduced norovirus reporting continued into early 2022. The reasons for the reduction in norovirus reporting are considered to be multifactorial. It is likely that the interventions implemented to control COVID-19 led to a reduction in enteric virus transmission. However, when considering the surveillance data reported here, the magnitude of the reduction is unlikely to be wholly attributable to these control measures alone. It is likely that other factors such as, but not limited to, changes in ascertainment, access to health care services and capacity for testing also contributed to the observed reduction due to changes in ascertainment and varied over time. The reduction in norovirus reporting to national surveillance during the 2019/2020 and 2020/2021 seasons also led to a period of low referral of norovirus-positive samples for characterisation. Therefore, trends for the 2019/2020, 2020/2021 and 2021/2022 seasons should be interpreted with caution.
SGSS data
SGSS data is England only, week number is calculated from specimen date and location is based on laboratory geography. Norovirus and rotavirus data include faecal and lower gastrointestinal tract specimen types only. Reporting may be subject to differences in regional ascertainment.
HNORS data
HNORS reporting is voluntary and variations may reflect differences in ascertainment or reporting criteria by region. National guidance recommends closure of the smallest possible unit in hospitals. Therefore, not all outbreaks reported to HNORS result in whole ward closure (some closures are restricted to bays only) and not all suspected cases are tested. Additionally, not all suspected cases are tested for norovirus, often only a proportion of individuals will be tested in any suspected outbreak.
Week number is calculated from date of first case onset for HNORS data.
From May to October 2019 and during February 2020, the HNORS website was temporarily offline. The reliance on manual data collation during this period may have negatively impacted ascertainment so trends should be interpreted with caution.
Norovirus characterisation data
Norovirus genotype characterisation data from the reference laboratory are subject to a reporting delay, and the numbers reported in any week may rise as further additional characterisation data become available.
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. 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)
3. 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)
4. 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)
5. 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)
6. 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.
Official statistics
Our statistical practice is regulated by the Office for Statistics Regulation (OSR). OSR sets the standards of trustworthiness, quality and value in the Code of Practice for Statistics that all producers of official statistics should adhere to.
UKHSA is committed to ensuring that these statistics comply with the Code of Practice for Statistics. This means users can have confidence in the people who produce UKHSA statistics because our statistics are robust, reliable and accurate. Our statistics are regularly reviewed to ensure they support the needs of society for information.