The UK Health Security Agency (UKHSA) is warning of a rise in norovirus cases and the potential for a second wave. Experts caution that even if you’ve already had the virus, you could be at risk of re-infection.
This latest warning follows new data which shows a shift in circulating strains as norovirus spreads across the UK. Laboratory reports have now reached their highest levels since UKHSA began tracking cases in this manner in 2014.
Laboratory-confirmed cases spanning the dates of February 3 to 16 of this year show that there were 29.4% higher than the previous two weeks. It also revealed that cases 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 soaring cases have been linked to the recently emerged GII.17 genotype. However, recent data shows 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?
The UKHSA cautions that norovirus can spread easily – especially in colder temperatures such as when people spend more time indoors. This is why it often peaks during the winter months.
- Abdominal pain
- Aching limbs
- Nausea and vomiting
- Diarrhoea
- High temperature
If you or someone you are concerned about is a young children, older adult or is an individual with weakened immune system, they are more vulnerable to severe symptoms that can lead to dehydration. To prevent this, anyone experiencing symptoms should ensure they stay 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 rise in cases may also be influenced by UKHSA’s enhanced testing capabilities and shifts in infection patterns since the COVID-19 pandemic, they conclude.