Cases of norovirus were almost three times higher in the last five weeks when compared to normal levels, Public Health England (PHE) has warned, following the easing of lockdown restrictions.
Norovirus, which is highly infectious and causes vomiting and diarrhoea, is normally associated with the winter months.
However, cases of the bug are currently increasing across England and "it is possible that unusual or out-of-season increases could be seen in the coming months following further easing of Covid-19 control measures", PHE said.
There has been a concentration of outbreaks particularly in nursery and childcare facilities, with far more incidents reported to PHE than would be expected in the summer months.
In the last five weeks, 154 outbreaks have been notified, compared to an average of 53 outbreaks for the same time period in the previous five years. An outbreak counts as two or more epidemiologically linked individuals with symptoms.
PHE said while young children were affected, there has also been a rise in all age groups.
Prof Saheer Gharbia, deputy director of PHE’s National Infection Service, said: "Norovirus, commonly known as the winter vomiting bug, has been at lower levels than normal throughout the pandemic with less opportunity to spread between people in the community, but as restrictions have eased we have seen an increase in cases across all age groups.”
Stay at home
Symptoms include sudden onset of nausea, projectile vomiting and diarrhoea, but can also include a high temperature, abdominal pain and aching limbs.
"Stay at home if you are experiencing norovirus symptoms and do not return to work or send children to school or nursery until 48 hours after symptoms have cleared,” Dr Gharbia said.
"As with Covid-19, hand washing is really important to help stop the spread of this bug, but remember, unlike for Covid-19 alcohol gels do not kill off norovirus, so soap and water is best."
Norovirus is easily transmitted through contact with infected people or contaminated surfaces.
Control measures used to reduce the spread of Covid-19, including isolation, increased handwashing and enhanced cleaning, are also used to control norovirus transmission.
As these controls have begun to be relaxed and people return to normal pre-pandemic behaviours, it’s likely norovirus transmission will go up, PHE said.
Prof Paul Hunter, of the University of East Anglia, said: “The increase of cases of norovirus in children almost certainly reflects the reduced immunity to this infection as a result of not being exposed to infection during the past 18 months.
“We have already started to see cases rising for some of the other respiratory viruses and this reminds us that as we come out of lockdown we are likely to start seeing many other infections rising that may cause problems for public health and the NHS.”