The UK’s Health Security Agency (UKHSA) says it is investigating after finding more than 100 cases of sudden hepatitis in children.
Doctors said they had seen "increasing" evidence the problem is linked to adenoviruses - a group of viruses that can cause illnesses such as the common cold and flu.
The HSA said it cannot rule out other possible causes such as Covid, which it is also investigating, but that an adenovirus has been identified in 40 out of the 53 cases so far tested.
The UK Health Agency’s lead investigator into the rise in cases, Dr Meera Chand, said that lockdown restrictions preventing young children from being exposed to the virus could be a factor in why it is hitting them the hardest.
In Britain, cases have reached 81 in England, 14 in Scotland, 11 in Wales and five in Northern Ireland, with the majority of patients under five years old.
No children in the UK have died, it was confirmed, after the World Health Organisation said there had been 169 cases globally with at least one child who had died from the illness.
