(Reuters) – On Saturday, the World Health Organization reported that one child died from acute hepatitis unknown in children. In addition to that, at least 169 children had suffered in twelve countries.

The WHO issued the figures as health authorities around the world investigate a mysterious increase in severe cases of hepatitis – inflammation of the liver – in young children.

According to the WHO, there were 21 cases of acute hepatitis from unknown origin reported by patients in Britain, Spain, Israel and Denmark as of April 21, according to the WHO. The WHO stated that 114 out of the 169 reported cases occurred in the United Kingdom.

It said that the cases were reported in children aged between one and 16 years old, with 17 requiring liver transplantation. The death it reported was not detailed and it did not specify where.

WHO reported that at least 74 of the cases had tested positive for a common cold virus called an adenovirus. It said that 20 cases of COVID-19 were tested. 19 other cases had a COVID-19/adenovirus combination.

WHO stated that it closely monitors the situation, and works with British healthcare authorities, as well as other partner countries and member states.

U.S. Health officials sent out an alert to doctors warning them about symptoms of pediatric liver disease. This could be linked to a common cold. It is part of larger investigation into unexplained cases in children of severe liver inflammation.