Reduced social mixing and fewer playtimes caused by the Covid-19 pandemic are being investigated as a possible cause of a hepatitis outbreak that began in the UK and spread to Europe and the US.
The lifestyle changes enforced during Covid lockdowns may mean children's defences to fight off illness are reduced, scientists fear.
British health officials have reported 108 cases of hepatitis, or liver inflammation, in young children under 10 since January, with eight patients having received a liver transplant. In the past week there have been 34 new cases.
The usual viruses that cause infectious hepatitis were not found in any of the cases and scientists and doctors are considering alternative sources, including Covid-19, other viruses and environmental factors.
They are investigating potential links to adenovirus, a common cold virus with sometimes serious symptoms.
During Covid lockdown, adenovirus case numbers dropped as children largely stopped interacting. The theory now is that may have lowered their immunity and they are now suffering the fall-out.
In the journal Eurosurveillance, scientists outline how decreased social mixing may have helped to suppress immunity.
“At the time of publication, the leading hypotheses centre around adenovirus – either a new variant with a distinct clinical syndrome or a routinely circulating variant that is more severely impacting younger children who are immunologically naive,” the journal article says.
“The latter scenario may be the result of restricted social mixing during the Covid-19 pandemic.”
Prof Graham Cooke, at Imperial College London, said: “We don’t know whether either [virus] is causing the problem or is just a bystander.
“There is going to be a group of children under the age of two who have not been exposed to the same number of viruses that they would have been exposed to normally. It is speculative but it is possible.”
Cases of the serious disease have been confirmed in the UK, Denmark, Ireland, the Netherlands, Spain and the US.
The World Health Organisation said that although there has been an increase in adenovirus in Britain, which is spreading at the same time as Covid-19, the potential role of those viruses in triggering the hepatitis remains unclear.
Some of the children have tested positive for coronavirus, but the WHO said genetic analysis of the virus was needed to determine if there were any connections between the cases.
It said no other links had been found between the children in the UK and none had travelled overseas recently. Laboratory tests are under way to determine if a chemical or toxin might be the cause.
