UK health security chiefs warn of second wave of norovirus

The UK could be facing a second wave of the winter vomiting bug, norovirus, the UK Health Security Agency has warned.

The latest figures show a rise in norovirus across the UK, with reported cases at the highest level in more than a decade. A shift in circulating strains means that those who have already been ill with norovirus this winter are at risk of catching it again.

Amy Douglas, a 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.”

Laboratory-confirmed cases in the two weeks from 3 to 16 February were 29% higher than the previous fortnight and more than double the five-season average (168%) for the same two-week period, the latest UKHSA data shows. This puts the prevalence at the highest level since the agency began reporting data this way in 2014.

The impact is particularly severe in hospitals and care homes, with cases highest among people aged 65 and over.

Douglas said: “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.”

The latest data also shows a shift in circulating strains. Cases of a strain known as GII.4, which has dominated in previous years, have sharply risen, now representing 29% of cases compared with just 10% three months ago. So far this year the recently emerged GII.17 strain has dominated, but now accounts for 59% of cases, down from 76% of cases in November.

Common symptoms of norovirus include nausea and vomiting, diarrhoea, high temperature, stomach pains and aching limbs. Some people, particularly young children, older adults and people with weakened immune systems, are more likely to develop severe symptoms, which can cause dehydration. Anyone with these symptoms is advised to drink plenty of fluids to avoid this.

UKHSA advises anyone with norovirus symptoms not to visit hospitals and care homes or return to work, school or nursery until 48 hours after symptoms have stopped and not to prepare food for others during this time period.

Cases usually start to decline around this time of year as the weather gets warmer and people spend less time indoors, but UKHSA said it is too soon to judge whether or not norovirus has peaked this season.

UKHSA experts estimate that reported cases represent only a small fraction of actual infections. For every case reported to national surveillance, approximately 288 cases occur in the community, suggesting about 3m cases annually in the UK.