Thirteen more children in the UK have been found to have sudden onset hepatitis, as a child in Ireland died from the severe liver condition.
Health officials around the world are investigating a sudden rise in cases of the condition in children.
The World Health Organisation said 348 probable cases of the acute form of hepatitis in children under 10 had been detected in more than 20 countries since it started monitoritng the situation early in April.
The European Centre for Disease Prevention and Control put the global case total at 450 by 3 May.
In the UK, the country which raised the alarm of a rise in cases first, the UK Health Security (UKHSA) recorded 176 child cases as of 10 May, mostly in children under five. Of the ill children, 128 lived in England, 26 in Scotland, 12 in Wales and nine in Northern Ireland.
Eleven of the UK children needed liver transplants but none died.
A child in Ireland died after being admitted to hospital as another received a liver transplant, Irish health officials said. Ireland has recorded six cases of hepatitis in children up to the age of 12 since April.
The outbreak of cases surprised health officials the world over and a global investigation has yet to determine precisely what is causing the uptick in cases.
The common viruses that cause hepatitis: hepatitis viruses A, B, C, and E; have not been detected in any of the cases reported worldwide.
The WHO said the most likely cause is adenovirus, a common cause of childhood illness, though other viruses including Covid-19 are being investigated.
Adenovirus is the most frequently detected virus in samples tested by the UKHSA. In a briefing on 6 May, the UKHSA said adenovirus was detected in 91 cases out of the 126 that had been tested.
Testing of seven children in England that needed a liver transplant found all seven had adenovirus.
The UKHSA advises ordinary hygiene measures, particularly thorough hand washing and making sure children wash their hands properly, to reduce the spread of infections including adenovirus.
Dr Meera Chand, Director of Clinical and Emerging Infections at UKHSA, said: “It’s important that parents know the likelihood of their child developing hepatitis is extremely low. 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.
“Our investigations continue to suggest that there is an association with adenovirus and our studies are now testing this association rigorously.”
The agency is working with the NHS and academic researchers to investigate the outbreak, she said.