Norovirus cases have surged by 31 per cent in two weeks amid the spread of a new variant named GII.17, new figures show.
Figures published by the UK Health Security Agency (UKHSA) show that infections were 31.6 per cent higher in the two weeks up to November 17 compared with the fortnight before.
Cases were almost double the five-season average for the same two-week period, according to the data.
Separate figures show that the number of norovirus outbreaks reported to the Hospital Norovirus Outbreak Reporting System (HNORS) since the start of the 2024/2025 season is 19.4 per cent higher than the five-season average.
Two-thirds (66.3 per cent) of cases reported so far this winter belonged to the GII.17 variant, which is one of three forms of the virus along with GI and GIV.
Norovirus is the most common infectious cause of vomiting and diarrhoea. Other symptoms include a high temperature, headaches, and aches in the harms and legs.
It spreads easily through contact with someone who has the virus or with contaminated surfaces.
While most people make a full recovery within two or three days, the virus can lead to dehydration, especially among the very young, the elderly or those with weakened immune systems.
Amy Douglas, epidemiologist at UKHSA, said: “We continue to see high levels of norovirus circulating in our communities. If you’ve caught the virus, take steps to avoid passing the infection on.
“If you have diarrhoea or vomiting, do not return to work, school or nursery until 48 hours after your symptoms have stopped and don’t prepare food for others in that time either. If you are unwell, avoid visiting people in hospitals and care homes to prevent passing on the infection in these settings.
“Washing your hands with soap and warm water and using bleach-based products to clean surfaces will also help stop infections from spreading. Alcohol gels do not kill norovirus so don’t rely on these alone.”
The UKHSA has said that norovirus activity had been unpredictable since the Covid pandemic, which impacted transmission of most seasonal viruses and led to waning population immunity.
The virus tends to peak in the winter months and causes pressure on hospitals, costing the NHS an estimated £100 million a year.
Older adults and immunocompromised patients are usually at higher risk of severe complications and death from norovirus, with around 80 fatalities per year in the UK and about 200,000 deaths globally.
Around two-thirds of outbreaks are in care homes but places such as hospitals, nurseries and schools are also at risk.
Earlier this year, health officials announced that the world’s first trial for a norovirus vaccine would go ahead in the UK.
The new mRNA vaccine from Moderna will enter final stages of testing within the next two weeks, with results so far showing it creates a “strong immune response”.
Experts believe the vaccine could stop people developing the vomiting and diarrhoea bug, which is linked to around 12,000 hospital admissions in the UK every year.
Currently, the only treatment available for people with serious illness in hospital is intravenous fluids.
