The World Health Organization (WHO) and the EU's health agency have issued warnings to other countries to be on the alert following a mysterious spike in cases of severe liver disease in children in the UK.
The UK's public health agencies are investigating 74 cases of hepatitis, an illness causing liver inflammation, in children since January.
Health experts are investigating the potential causes, as the usual viruses causing the illness have not been detected in these cases.
The UK's Health Security Agency (UKHSA) said on April 12 that 49 the confirmed cases are in England, 13 are in Scotland and the remainder are in Wales and Northern Ireland.
The EU's European Centre for Disease Prevention and Control (ECDC) said most cases involved children ages 2 to 5.
It said some children had suffered acute liver failure and a "small number have required liver transplantation."
It said there were no travel links between the affected children.