A further 20 cases of hepatitis have been confirmed in children aged 10 and under, the UK Health Security Agency (UKHSA) has said.
It brings the total number of cases across the UK to 222, as of Wednesday May 25.
Of the confirmed cases of sudden onset hepatitis, 158 are resident in England, 31 are in Scotland, 17 are in Wales and 16 are in Northern Ireland, the UKHSA said.
The cases are mainly in children under five, who showed initial symptoms of gastroenteritis illness (diarrhoea and nausea) followed by jaundice.
No children have died.
Covid symptoms NHS
A small number of children aged over 10 are also being looked into as part of UKHSA’s investigation.
The UKHSA is investigating whether prior Covid infection is behind the surge, but said there was “no evidence” of the condition being linked to Covid vaccinations.
Scientists had also been looking into a link between the hepatitis cases and dogs, but ruled it out last week.
A more likely culprit is thought to be adenovirus, a common virus which causes infection.
Dr Renu Bindra, the UKHSA’s incident director, said parents should be “alert” to the symptoms of hepatitis.
Dr Bindra said: “Our investigations continue to suggest an association with adenovirus, and we are exploring this link, along with other possible contributing factors including prior infections such as Covid.
“We are working with other countries who are also seeing new cases to share information and learn more about these infections.
“We continue to remind everyone to be alert to the signs of hepatitis, particularly jaundice – look for a yellow tinge in the whites of the eyes, and contact your doctor if you are concerned.”