Hepatitis is an inflammation of the liver, which filters the blood, helps fight infections and processes nutrients.

At least one child is dead and 17 have required liver transplants from the disease. The majority of the cases, 114, were reported in the United Kingdom, while 13 were from Spain, 12 from Israel, nine in the USA, and a smaller number of cases in Denmark, Ireland, the Netherlands, Italy, Norway, France, Romania and Belgium.

Most of the cases had no fever, nor any of the common viruses that typically cause acute viral hepatitis, such as adenoviruses, which cause hepatitis A, B, C, D and E.

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

According to the Saturday statement, the clinical syndrome "among identified cases is acute hepatitis (liver inflammation) with markedly elevated liver enzymes," with many suffering gastrointestinal issues such as diarrhea, abdominal pain and vomiting "preceding presentation with severe acute hepatitis" along with increased levels of liver enzimes or alanine aminotransaminase and jaundice.