Less social mixing is being considered as the cause of serious outbreak of acute liver disease among young children which was first reported in Scotland.
A total of 74 children in the UK, have contracted a version of acute hepatitis which is not linked to normal strains of the disease.
One line of inquiry by experts is a link to adenovirus, a common cold virus which can cause more serious symptoms including gastrointestinal illness in young children.
Cases of adenovirus in children were far lower during lockdown, and experts believe that the lack of exposure to the virus may have lowered their immunity, meaning they are suffering worse effects now that restrictions are lifted.
In a paper for the journal Eurosurveillance on 14 April, scientists investigating the cses in Scotland said decreased social mixing may have played a part in suppressing immunity to adenovirus.
They said: “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 naïve.
“The latter scenario may be the result of restricted social mixing during the Covid-19 pandemic.”
In Scotland, five out of the 13 hepatitis cases also tested positive for adenovirus. Five of the 13, two of whom had also had adenovirus, tested positive for Covid-19. None of the children affected have had a Covid vaccine.
Most were aged three; seven were girls and six were boys all were in hospital for at least six days. Five are still in-patients.
Professor Graham Cooke, an expert in infectious diseases at Imperial College London, said that both Covid and adenovirus were in high circulation at the time the cases first emerged, adding: “We don’t know whether either [virus] is causing the problem or is just a bystander.”
He added: “ 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.”