The World Health Organization (WHO) has sounded an alert about a mysterious liver disease outbreak affecting children in Europe and the United States as it said at least one death has been reported due to the ailment.

The WHO said that it has so far received reports of at least 169 cases of “acute hepatitis of unknown origin” from a dozen countries.

The cases were reported in children ranging from one month to 16 years of age, and 17 of those who fell ill required liver transplants. The UN health agency did not mention in which country the death occurred.

The first cases were recorded in the UK, where 114 children were infected.

“It is not yet clear if there has been an increase in hepatitis cases, or an increase in awareness of hepatitis cases that occur at the expected rate but go undetected,” WHO said in a statement.

Experts say the cases may be linked to a virus commonly associated with colds, but further research is still going on.

“While adenovirus is a possible hypothesis, investigations are ongoing for the causative agent,” WHO said.

The virus has been detected in at least 74 of the cases. At least 20 of the children tested positive for the coronavirus, it added.

WHO said affected countries are stepping up their surveillance of hepatitis cases in children.

Also read: Disposable coffee cups shed tonnes of microplastics into your cup