Guidance

Quality and methodology information: national norovirus and rotavirus reports

Published 25 September 2025

Applies to England

About this report

This report outlines the quality and methodology information (QMI) relevant to the national norovirus and rotavirus surveillance reports official statistics release published by the UK Health Security Agency (UKHSA). This QMI report supports users in understanding the strengths and limitations of these statistics, ensuring UKHSA is compliant with the quality standards stated in the Code of Practice for Statistics. The report covers the following areas:

1. The strengths and limitations of the data used to produce the statistics.
2. The methods used to produce the statistics.
3. The quality of the statistical outputs.

About the statistics

Norovirus, also known as winter vomiting disease, causes gastroenteritis and is highly infectious. The virus is easily transmitted through contact with infected individuals from one person to another. Norovirus outbreaks are common in semi-enclosed environments such as hospitals, nursing homes, schools and cruise ships and can also occur in restaurants and hotels.

Since 6 April 2025, norovirus has been a notifiable causative agent, meaning that laboratories in England that test human samples for norovirus are legally required to report any positive norovirus test results to UKHSA within 7 days.

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 and an overall increase in norovirus activity when the GII.17 genotype dominated during the 2024/2025 season. Both of which place unexpected pressure on the health and social care sectors.

Rotavirus is also a common cause of gastroenteritis, particularly in infants and young children. A rotavirus vaccine was introduced to the national vaccination schedule for babies in 2013, alongside other routine childhood immunisations.

These official statistics present positive norovirus and rotavirus laboratory reports and norovirus outbreaks in hospital settings in England each reporting season, which begins in week 27 of the year, running roughly from July in one year to June in the next. Data is reported by season rather than calendar year, in order to capture the winter peak of activity in one reporting period. Week numbers are based on the ISO 8601 standard.

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 will change.

Geographical coverage:

• England

Publication frequency:

• weekly from mid-autumn to mid-spring
• monthly from mid-spring to mid-autumn

The precise timing of the change in publication frequency is dependent on norovirus activity at that time.

Changelog

First published on 25 September 2025.

Contact

Lead analysts: Gastrointestinal Infections, Food Safety and One Health (GIFSOH) Division

Contact: NoroOBK@ukhsa.gov.uk

Suitable data sources

Statistics should be based on the most appropriate data to meet intended uses.

This section describes the data used to produce the statistics.

Data sources

The national norovirus and rotavirus reports present data from 3 systems which collectively describe recent trends:

1. The Second Generation Surveillance System (SGSS).
2. The Hospital Norovirus Outbreak Reporting System (HNORS).
3. The Modular Open Laboratory Information System (MOLIS).

Second Generation Surveillance System

SGSS is the national laboratory reporting system which stores and manages laboratory test result information from diagnostic laboratories in England. Positive laboratory test results for norovirus and rotavirus are reported by NHS trusts to SGSS on a routine basis. Since 6 April 2025, norovirus has been a notifiable causative agent in schedule 2 of the 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 UKHSA within 7 days of the result becoming available. SGSS norovirus and rotavirus data is for England only, with the location based on the geography of the laboratory reporting the positive result, and includes faecal and lower gastrointestinal tract specimen types only. Week number is calculated from specimen date, in years with a week 53 (2015 and 2020) data is combined with week 52 data to avoid distortion of the chart.

Hospital Norovirus Outbreak Reporting System

HNORS is a live web-based platform maintained by the GIFSOH Division in UKHSA and used by acute NHS trust hospitals in England to report suspected and confirmed norovirus outbreaks. HNORS captures information on the disruptive impacts these outbreaks have in hospital settings, for example whether wards have been closed to admission. Week number is calculated from date of first case symptom onset for HNORS data. The norovirus surveillance team carries out periodic quality checks on HNORS data and follows up where necessary with NHS colleagues.

Modular Open Laboratory Information System

The UKHSA Enteric Virus Unit (EVU) routinely undertakes characterisation of norovirus-positive samples shared by NHS trusts to monitor the diversity of circulating genotypes and strains. EVU results are stored on and accessed through MOLIS.  Molecular surveillance enables monitoring of the diversity of circulating strains and timely detection of novel strains or re-emergence of existing strains that could lead to a strain replacement event. Week number is calculated from the date the sample was received by EVU.

Strengths and limitations of the data

The data that we use to produce statistics must be fit for purpose. Poor quality data can cause errors and hinder effective decision making.

We have assessed the quality of the source data against the data quality dimensions in the Government Data Quality Framework. This section covers the quality of the data that was used to produce the statistics, not the quality of the final statistical outputs. The Quality summary section below covers the quality of the final statistical outputs.

Each data source is described below with respect to the following quality dimensions:

• Accuracy is about the degree to which the data reflects the real world. This can refer to correct names, addresses or represent factual and up-to-date data.
• Completeness describes the degree to which records are present. For a data set to be complete, all records are included, and the most important data is present in those records. This means that the data set contains all the records that it should and all essential values in a record are populated. Completeness is not the same as accuracy as a full data set may still have incorrect values.
• Uniqueness describes the degree to which there is no duplication in records. This means that the data contains only one record for each entity it represents, and each value is stored once. Some fields, such as National Insurance number, should be unique. Some data is less likely to be unique, for example geographical data such as town of birth.
• Consistency describes the degree to which values in a data set do not contradict other values representing the same entity. For example, a mother’s date of birth should be before her child’s. Data is consistent if it doesn’t contradict data in another data set. For example, if the date of birth recorded for the same person in 2 different data sets is the same.
• Timeliness describes the degree to which the data is an accurate reflection of the period that it represents, and that the data and its values are up to date. Some data, such as date of birth, may stay the same whereas some, such as income, may not. Data is timely if the time lag between collection and availability is appropriate for the intended use.
• Validity describes the degree to which the data is in the range and format expected. For example, date of birth does not exceed the present day and is within a reasonable range. Valid data is stored in a data set in the appropriate format for that type of data. For example, a date of birth is stored in a date format rather than in plain text.

SGSS

SGSS: Accuracy

Laboratory surveillance is based on well-validated testing occurring in NHS trusts. Laboratories may use different test methods to identify norovirus in clinical samples, including reverse transcriptase polymerase chain reaction (RT-PCR) testing and immunological assays. Different test methods have different levels of sensitivity and specificity for norovirus. RT-PCR is currently considered the gold standard for diagnosis of viral gastroenteritis including norovirus and rotavirus. The most common rotavirus screening tests used by hospital laboratories in the UK have been found to have high false positive rates when compared with reference laboratory PCR tests and lower positive predictive value during the low season months of July to November.

Laboratory surveillance is based on well-validated testing occurring in NHS trusts. Laboratories may use different test methods to identify norovirus in clinical samples, including reverse transcriptase polymerase chain reaction (RT-PCR) testing and immunological assays. Different test methods have different levels of sensitivity and specificity for norovirus. RT-PCR is currently considered the gold standard for diagnosis of viral gastroenteritis including norovirus and rotavirus. The most common rotavirus screening tests used by hospital laboratories in the UK have been found to have high false positive rates when compared with reference laboratory PCR tests and lower positive predictive value during the low season months of July to November.

SGSS: Completeness

Under-ascertainment is a recognised challenge in norovirus and rotavirus surveillance, with positive laboratory reports representing only a small fraction of community cases and cases presenting to primary care. A longitudinal study of infectious intestinal disease in the UK between 2008 and 2009 estimated that for every norovirus case reported to the national surveillance system, there were 288 (95% confidence interval (CI): 239 to 346) cases in the community and 12.7 (95% CI: 8.8 to 18.3) GP consultations.

Furthermore, the level of under-ascertainment may vary by sub-group. Sampling, testing and reporting criteria are known to vary by region, and diagnostic criteria may differ between age groups. In addition, samples sent for microbiological confirmation are collected in a small proportion of community outbreaks.

Laboratories that test human samples in England are legally required to report positive norovirus test results. There is no equivalent requirement for positive rotavirus test results. As laid out in UKHSA laboratory reporting guidelines, several fields are mandatory when filling out a test report for submission to SGSS: reporting laboratory, patient identification markers, patient date of birth, patient sex, organism, specimen type and specimen date. All the variables required to produce the statistics and figures contained in the norovirus and rotavirus report are therefore mandatory. However, these fields may not always be fully populated.

SGSS: Uniqueness

SGSS records are deduplicated at the episode level, whereby an episode constitutes each positive result for a patient in a defined period. Infectious organism, specimen date, and patient details including NHS number, forename, surname, hospital number, date of birth, sex, and postcode are used for deduplication. For norovirus and rotavirus, the default SGSS episode length of 2 weeks is used, retaining the earliest specimen date. Cases with multiple positive samples of the same virus where specimens were taken more than 2 weeks apart will therefore be represented in the data more than once. Therefore, the report describes norovirus and rotavirus activity as the number of laboratory reports, rather than cases.

SGSS: Consistency

Once laboratory results have been reported to SGSS, records are subject to several cross-validation processes to ensure they do not contradict other data sources. Patient data is validated against the Personal Demographics Service and each record is updated with additional data received from NHS England Spine. Each week’s data is also compared to the data for the current season and the 5 seasons used to calculate the 5-season average to ensure consistency across the season.

SGSS: Timeliness

Since 6 April 2025, laboratories have been legally required to report positive norovirus test results to SGSS within 7 days from the day on which the laboratory becomes aware of the test result, as per the Health Protection (Notification) Regulations 2010. There is no equivalent requirement for positive rotavirus test results. All data is subject to a delay between specimen date and result report date. Laboratory data is reported to SGSS on a daily basis but follows a lag as samples need to be transported to the relevant trust laboratory, processed, and reported. Typically, there is a lag of around 1 to 2 days between the date a sample is taken and the date the result is reported, though batch reporting, whereby a large number of historical samples are reported on the same day, can sometimes occur. SGSS is a live database that is managed by UKHSA and therefore there is no delay between data submission and availability.

SGSS: Validity

Once laboratory results have been reported to SGSS, records are subject to validation processes to ensure that, for example, dates are provided in the correct format, only numeric values are provided for age fields and field lengths do not exceed maximum values. Records that do not meet minimum requirements are flagged as ‘not valid’ and therefore excluded from the live system.

HNORS

HNORS: Accuracy

Outbreaks are recorded as ‘laboratory-confirmed’ if at least one case (staff or patient) has tested positive for norovirus. However, not all suspected cases are tested for norovirus; often only a proportion of individuals will be tested in any suspected outbreak. In the absence of laboratory confirmation, outbreaks are assigned as ‘suspected norovirus outbreaks’ by the infection, prevention and control staff responsible for managing the outbreak in each NHS trust who assess the characteristics of the outbreak against the definitions provided by UKHSA. The symptom onset date of the first case is used as the report date for the outbreak, which may misrepresent the true start date of the outbreak due to inaccurate recall or prior undetected symptomatic or asymptomatic cases. The proportion of reported outbreaks that are laboratory-confirmed may be under-reported if the outbreak is confirmed after the initial report and HNORS users do not update the outbreak record.

HNORS: Completeness

Reporting to HNORS is voluntary and while trusts are not required to report their outbreaks within a specified timeframe, they are encouraged to report weekly. The proportion of the true burden of suspected and confirmed norovirus outbreaks in hospitals that are reported to HNORS is currently unknown and regional variations may reflect differences in ascertainment or reporting criteria. For outbreaks that are reported to HNORS, the UKHSA norovirus surveillance team follows up with relevant trusts where HNORS records are incomplete. 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.

HNORS: Uniqueness

The UKHSA norovirus surveillance team removes confirmed duplicate records based on data quality review and follow-up with trusts. There are no data validation restrictions preventing a hospital from reporting the same outbreak twice, and for this reason UKHSA encourages HNORS users in the same trust to liaise with each other to prevent duplication. These processes ensure minimal duplication of records.

HNORS: Consistency

There are no further data sources available against which HNORS data can be checked. However, each week’s data is compared to the previous week and the 5 seasons used to calculate the 5-season average to ensure consistency across the season. The UKHSA norovirus surveillance team follow up with relevant HNORS users if review of HNORS data reveals data consistency issues.

HNORS: Timeliness

Hospitals are not required to report their outbreaks within a specified timeframe and some batch reporting may take place, particularly over the summer when norovirus activity is low. Therefore, outbreak counts in the weeks immediately prior to report publication may be under-ascertained. HNORS is a live web-based application that is managed by UKHSA and therefore there is no delay between data submission and availability.

HNORS: Validity

Data validation restrictions prevent HNORS users from entering data for particular fields in incorrect formats, for example dates must be selected from the calendar drop down. Further validity checks are undertaken throughout the data cleaning process, for example all outbreaks with at least one norovirus positive same are coded as ‘laboratory confirmed’.

MOLIS

MOLIS: Accuracy

The laboratory methods used at the EVU for genome analysis and genotype assignment have been validated in compliance with internal UKSA processes and are accredited by the UK Accreditation Body (UKAS) under ISO 15189:2022 (UKAS 8825). Norovirus-positive samples are assigned to genogroups and genotypes in accordance with the latest norovirus classification scheme.

MOLIS: Completeness

NHS trusts refer norovirus-positive samples to the EVU for characterisation on a voluntary basis. Not all NHS trusts participate in genotype surveillance and not all samples from participating trusts are submitted for testing.  UKHSA regional and collaborating laboratories are requested to refer samples associated with any hospital or community outbreak as well as samples from sporadic norovirus cases each week. During periods of unusual or high activity these laboratories may be asked to increase referrals and NHS diagnostic laboratories may be asked to refer samples for a specified time period. Information on all samples received for testing are reported onto MOLIS, including if there was no norovirus detected. Sample date is not consistently provided, therefore week number is calculated from the date the sample was received by EVU.

MOLIS: Uniqueness

All referring laboratories are required to provide sender details and at least two pieces of patient identifying information on the request form submitted alongside any samples sent for testing. If patient identifiers are not provided, the EVU will contact the sender directly to obtain the relevant information. All samples received by the EVU are assigned a unique MOLIS number.

MOLIS: Consistency

The genotyping data set is unique and there are no other sources of information against which MOLIS data can be compared.

MOLIS: Timeliness

Norovirus genotype and GII.4 strain characterisation data from the reference laboratory is subject to a reporting delay because it takes time for the sample to arrive at EVU, undergo genome analysis and be subjected to validation processes. Only results for samples which fully completed this process will be included in the analysis. Numbers reported in recent weeks may rise further if additional characterisation data becomes available.   

MOLIS: Validity

Test results are uploaded onto MOLIS and subject to further technical and medical validation prior to reporting.

Sound methods

Statistical outputs should be made using the best available methods and recognised standards. This section describes how the statistics were produced and quality assured.

Data set production

The national norovirus and rotavirus surveillance report is produced via a reproducible analytical pipeline (RAP), in which key statistical and analytical processes are automated. Connections to SGSS and MOLIS are automated within the RAP, with live data extracted directly into R via an SQL query, while HNORS data is extracted and loaded into the RAP manually. Additional input validation and data cleaning steps are implemented on an automated basis through the RAP. The final report is rendered via an R Markdown file featuring a combination of dynamically generated charts, statistics and text, and static contextual information.

Each surveillance report includes data up to the Sunday 4 days prior to the date of publication (see Trade-offs between timeliness and accuracy section below). Production of the report begins on Monday of the week of publication, and the report is published on Thursday of that week. Consequently, the data included in the report is limited to that which is available from the sources listed above as of that Monday.

The 5-season average is based on the arithmetic mean of weekly counts for the baseline period, which is defined as the 5 seasons prior to the current season, not including the seasons of 2019/2020, 2020/2021 and 2021/2022 (see Impact of COVID-19 pandemic on surveillance section below). To estimate 95% confidence intervals for the mean it is assumed that the sample mean follows Student’s t-distribution, given the small sample size (n=5) available for each weekly estimate.

For age and regional breakdown of norovirus surveillance data, rates per 100,000 people are calculated using the most recent mid-year population estimates available from the Office for National Statistics. As mid-year population estimates for a given year are published during the following year, there is a lag between the population estimates and the norovirus surveillance data.

Quality assurance

Transformation of the data ready for analysis, production of the report, charts and accompanying spreadsheet have been automated. This reduces the risk of human error as responsible analysts do not have to manually update charts or copy and paste between documents. Data is checked procedurally at each stage of the pipeline to ensure that it is of the right type, and a step will not run if the input data is formatted in an unexpected way, for example, if a step is expecting a date but receives a number. The report, charts and spreadsheet undergo visual inspection and are sense-checked by the lead analytical and senior responsible officer (who signs off the final version). Intermediate data sets are saved at several intervals during report production, facilitating troubleshooting if unexpected outputs are produced. The pipeline is subject to comprehensive peer review on a periodic basis. UKHSA actively maintains a log documenting quality assurance indicators, issues and actions.

Confidentiality and disclosure control

Personal and confidential data is collected, processed, and used in accordance with the UKHSA Privacy Notice. All UKHSA staff with access to personal or confidential information must complete mandatory information governance training, which must be refreshed every year. Information is stored on computer systems that are kept up-to-date and regularly tested to make sure they are secure and protected from viruses and hacking. UKHSA staff do not store data on their own laptops or computers. Instead, data is stored centrally on UKHSA secure servers.

Laboratory surveillance statistics are aggregated to national level and disaggregated by region and by age. The smallest relevant effective population (the UK region with the smallest population) is sufficiently large that no statistical disclosure controls are necessary, as per the NHS information standard ISB1523: Anonymisation Standard for Publishing Health and Social Care Data. Molecular characterisation data is aggregated to national level, where the risk is low, and only the most common genotypes in each genogroup are reported with typing information. Therefore, no statistical disclosure controls are necessary. are necessary.

Geography

The statistics in this report pertain to norovirus and rotavirus activity in England. Laboratory surveillance statistics are calculated using reports from English laboratories only; rates per 100,000 people are shown for each UKHSA region. Only suspected and confirmed norovirus outbreaks from  acute NHS trusts in England are reported. Only laboratories in England refer norovirus-positive samples to EVU for genome analysis.

Quality summary

The Code of Practice for Statistics states that quality means that statistics:

• fit their intended uses
• are based on appropriate data and methods
• are not materially misleading

Quality requires skilled professional judgement about collecting, preparing, analysing, and publishing statistics and data in ways that meet the needs of people who want to use the statistics.

This section assesses the statistics against the European Statistical System dimensions of quality.

Relevance

There is a clear demand for timely norovirus and rotavirus statistics (see Uses and users section below). We continue to make improvements to the publication to better meet user needs. A user engagement survey was carried out from 10 April to 13 June 2025 to understand users’ views on the report and to seek suggestions on how it could be improved (see User engagement section below). In response to feedback gathered through the survey, the report was expanded to include breakdowns of norovirus laboratory reports by age and geographic region of the reporting laboratory. The molecular surveillance section was also restructured, presenting the key statistics in 2 tables with accompanying commentary. These changes were implemented in the first report of the 2025/2026 reporting season. By providing this range of different outputs, we can better cater to the needs of different users from a range of backgrounds, in line with the Office for National Statistics user personas. User feedback indicating support for more timely reporting also informed the decision to reduce the lag period for data included in the report (see Trade-offs between timeliness and accuracy section below).

Accuracy and reliability

The accuracy of the statistics is largely dependent on the accuracy of the source data. The role of randomness in laboratory reporting is quantified and visualised via 95% confidence intervals around the 5-season average. As all 3 primary data sources used in the production of the report are live systems, the counts and statistics are based on provisional data. Counts and statistics for a particular time period are updated as additional test results and outbreaks are reported, and as additional verification, data cleaning, and recoding are completed. Where data necessary to generate a statistic or figure is missing for one or more records, caveats explaining how missing values have been handled are provided in the text and as notes under figures or in the accessible spreadsheet.

Timeliness and punctuality

The national norovirus and rotavirus reports are official statistics and are pre-announced at least 28 days in advance, in line with the Code of Practice for Statistics. Provisional publication dates for the season ahead and can be found on the UKHSA release calendar. Typically, reports are announced at least 6 months in advance.

By default, the statistics are published weekly from mid-autumn to mid-spring (week 41 to week 15 of the following year) and monthly from mid-spring to mid-autumn (week 19 to week 39). More timely release in colder months allows users to take appropriate actions when viral activity is typically highest. If activity is unseasonably high, the release schedule may be modified to allow for weekly reports to continue beyond the planned period.

Accessibility and clarity

We currently publish 2 products as part of this statistical release:

1. The main official statistics report.
2. A supplementary spreadsheet containing aggregated data counts that underpin statistics and visualisations included in the report.

The official statistics report has been published in HTML format since July 2023, making the content easier to access and read across different devices. The report is written in plain English, with technical vocabulary kept to a minimum and, where its use is necessary, explained in accessible terms. The report includes data visualisations such as charts and tables that help communicate the data. All visualisations are designed to be colour-blind friendly. Colours in charts are chosen to ensure there is always sufficient contrast for different elements to be distinguished.

A supplementary spreadsheet has been published alongside the official statistics report since 28 August 2025. The spreadsheet is published in ODS format and follows Government Analysis Function guidance on spreadsheet accessibility. Each worksheet contains only one table and a descriptive header. Appropriate shorthand is used to describe missing data and no cells are left empty. Detailed background information and data caveats for the statistics presented in each table are explained in the separate notes worksheet.

Coherence and comparability

The national norovirus and rotavirus report is the only summary of norovirus and rotavirus laboratory surveillance, hospital norovirus outbreak and molecular surveillance norovirus data routinely published by the UKHSA.

Norovirus became a notifiable causative agent in the England following an amendment to the Health Protection (Notification) Regulations 2010 on 6 April 2025. The UKHSA norovirus surveillance team has continued to monitor laboratory surveillance data since then to understand the extent to which the amendment resulted in more timely notification of positive norovirus test results to SGSS and, consequently, the extent to which there was a meaningful disruption in the time series which could complicate comparison of counts before and after the amendment.

Other devolved administrations in the UK publish norovirus surveillance statistics (see Related statistics). However, UKHSA norovirus statistics for England may not be compared directly with statistics produced by the devolved governments. UKHSA and devolved governments have not adopted a standardised approach to norovirus statistics production, and therefore there may be critical differences between respective authorities’ approaches to data management, including de-duplication, cleaning and filtering.

Impact of COVID-19 pandemic on surveillance statistics

The UKHSA relaunched the National norovirus and rotavirus official statistics report after it was temporarily suspended due to quality issues with the data from the 3 aforementioned data sources during the COVID-19 pandemic. Additional analyses of this data were undertaken and demonstrated the quality of this data was comparable to the data collected before the pandemic and therefore reporting was allowed to resume as Official Statistics from 9 October 2022 . 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 period 2020/2021 is available at National norovirus and rotavirus bulletins 2020 to 2021: management information. Data covering the period 2021/2022 is available at National norovirus and rotavirus bulletins 2021 to 2022: management information.National norovirus and rotavirus bulletins 2021 to 2022: management information.

The 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.  There are several reasons why reported norovirus activity declined during the pandemic. It is likely that the interventions implemented to control COVID-19 led to a reduction in norovirus 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. The relative impact of these contributory factors likely varied over time. The reduction in norovirus reporting to national surveillance during the 2019/2020, 2020/2021 and 2021/2022 seasons also led to a period of low referral of norovirus-positive samples for characterisation. Therefore, norovirus and rotavirus reports from the 2019/2020, 2020/2021 and 2021/2022 are omitted from the baseline period used to calculate the 5-season mean.

Trade-offs between timeliness and accuracy

The data included in the report is limited to that which is available from the sources listed above as of the Monday 3 days prior to publication.

From the 2025/2026 reporting season onwards, the National norovirus and rotavirus report has included positive-norovirus samples with specimen dates up to the Sunday 4 days prior to publication, rather than the Sunday 11 days prior (as previously) to ensure timely release of information. The results of an internal analysis carried out in May 2025 suggested that there was a slight decrease in data completeness with a 4-day data lag relative to an 11-day data lag. However, following consultation with the UKHSA statistics quality assurance team and review of user feedback, the norovirus surveillance team felt that the provision of more timely data to users with a 4-day data lag justified the trade-off. Report counts in the most recent weeks can be expected to rise as more test results for these weeks are reported to SGSS.

Uses and users

Users of statistics and data should be at the centre of statistical production, and statistics should meet user needs.

This section explains how the statistics are used, and how we understand user needs.

Appropriate use of the statistics       

The national norovirus and rotavirus report integrates data from 3 distinct systems, presenting positive laboratory reports of norovirus and rotavirus, norovirus molecular characterisation results and reports of suspected and confirmed norovirus outbreaks in acute NHS trust hospitals. While each system has its own limitations, as detailed previously, their combined use provides a reasonable assessment of recent trends in norovirus and rotavirus activity, even if they do capture all aspects of their epidemiology fully.

Known users and uses

Known users of the statistics are primarily in clinical care and public health. The statistics are also used by the general public, media, and academia and research. The norovirus and rotavirus surveillance team is aware that the statistics have been used in several different ways, including:

• informing infection prevention and control measures
• assessing risk in the food industry
• winter planning in the health and social care sector
• planning and designing clinical and public health studies
• understanding rates of staff sickness
• assessing and managing personal risk

User engagement

UKHSA recently carried out a norovirus and rotavirus statistics user engagement survey. The survey ran from 10 April to 13 June 2025 and asked users to provide information about who they are and how they use the publication. Users were also asked which parts of the publication they find most and least useful as well as suggestions for improvements to the statistics. UKHSA is keen to maximise the value of the publication for users and will look to implement the findings of the survey throughout the 2025 to 2026 season.

Related statistics

UKHSA:

• Gastrointestinal infections and outbreak statistics for England (UKHSA)

The following links go to publications or releases by bodies other than UKHSA and, as such, UKHSA is not responsible for their content:

• Communicable disease surveillance reports for Wales (Public Health Wales), which contain an update on norovirus activity
• Laboratory reports of norovirus in Scotland (Public Health Scotland)
• Gastrointestinal infections surveillance in Northern Ireland (Public Health Agency Northern Ireland)