The UK Health Security Agency (UKHSA) has issued a fresh health warning
The UK Health Security Agency (UKHSA) is warning that norovirus cases are on the rise – and says there could be a second wave. The experts caution that even those who have already had the virus this winter could be at risk again.
The fresh warning comes as new data shows a shift in circulating strains, with the latest UKHSA data showing norovirus cases spreading across the UK. Laboratory reports are now at the highest levels since the agency began reporting data this way in 2014.
Laboratory-confirmed cases from February 3 to 16, 2025, were 29.4% higher than the previous two weeks and exceeded the five-season average for the same period by 168.0%. The impact is especially severe in hospitals and care homes, with the highest case numbers among individuals aged 65 and older. While cases typically begin to decline as temperatures rise around this time of year, it remains uncertain whether norovirus has peaked this season.
The rise in cases this season has been linked to the recently emerged GII.17 genotype. However, the latest data indicates a growing presence of the more common GII.4 genotype.
Before GII.17 emerged, GII.4 was typically the most frequently detected strain each winter. While GII.17 remains dominant, accounting for 59% of cases, its prevalence has declined from 76% since November. At the same time, the GII.4 strain has surged, now making up 29% of cases compared to just 10% three months ago.
The agency warns: “This means that people who have already had norovirus this season may catch it again, as having one genotype does not fully protect against the other. However, at present there is no indication that either GII.17 or GII.4 leads to more severe illness.”
What are symptoms of norovirus?
- Nausea and vomiting
- Diarrhoea
- High temperature
- Abdominal pain
- Aching limbs
Certain individuals, including young children, older adults, and those with weakened immune systems, are at a higher risk of severe symptoms that may lead to dehydration. It is important for anyone experiencing these symptoms to stay well-hydrated by drinking plenty of fluids.
Amy Douglas, Lead Epidemiologist at UKHSA, said: “Norovirus levels are still exceptionally high and now with multiple genotypes spreading at the same time, people could end up getting infected more than once this season. We are seeing the biggest impacts in health and social care settings, such as hospitals and care homes.
“Symptoms of norovirus can be more severe in older adults, young children and those who are immunocompromised. If you have diarrhoea and vomiting, please do not visit hospitals and care homes or return to work, school or nursery until 48 hours after your symptoms have stopped and don’t prepare food for others, as you can still pass on the virus during this time.
“Alcohol gels do not kill norovirus. Wash your hands with soapy warm water and clean surfaces with bleach-based products where possible to help stop infections from spreading.”
The rise in norovirus cases this season is likely driven by the GII.17 genotype, as previous immunity to this strain is low. However, the increase may also be influenced by UKHSA’s enhanced testing capabilities and shifts in infection patterns since the COVID-19 pandemic.
The UKHSA explains that norovirus spreads more easily in colder temperatures when people spend more time indoors. This is why it typically peaks during the winter months.