Norovirus
Last updated on Wednesday, 7 October 2026 at 03:57pm
Summary
- Topic
- norovirus
- Category
- cases
- API name
norovirus_cases_count
Rationale
Norovirus infections increase each year during the winter. They are a major cause of pressure on health and social care services.
Testing helps UKHSA monitor norovirus activity and strains that are circulating. New or unusual genotypes can cause additional pressure on health and social care services. This can happen outside the usual seasonal period.
Definition
This metric shows the weekly number of positive laboratory reports for norovirus in England.
The date shown is the Monday of the week the sample was taken for testing.
Methodology
Norovirus cases are identified by testing samples from people with symptoms that could be caused by norovirus. These symptoms usually include vomiting and diarrhoea. Samples may also be taken from people who are part of a suspected outbreak.
Laboratories test stool or vomit samples for norovirus using a polymerase chain reaction (PCR) test.
Each season about 10% of positive samples are sent to the UKHSA national reference laboratory. Further testing is carried out to identify the norovirus genotype.
Since April 2025, norovirus has been a notifiable causative agent under The Health Protection (Notification) (Amendment) Regulations 2025. This means diagnostic laboratories must notify UKHSA within 7 days when they identify norovirus. Second Generation Surveillance System (SGSS) norovirus data covers England only. The location is based on the geography of the laboratory that reported the positive result.
The data include feacal and lower gastrointestinal tract specimen types only.
Caveats
The number of reported cases is lower than the actual number of norovirus infections. Most people with norovirus are not tested and manage their symptoms at home.
Some groups are more likely to have severe or longer-lasting illness and may be more likely to be tested. These include:
- young children
- older people
- people who are immunocompromised
- other vulnerable groups
Norovirus outbreaks are common in settings where people live, work or spend time close together. These include nurseries, schools, hospitals and care homes.
Only a small proportion of cases are tested. Testing is more likely to take place in health and social care settings.
Bank holidays can affect the number of tests completed in a week. This may be because access to healthcare and testing services changes during bank holidays.