Adenoviruses are a common cause of cold-like illnesses and can cause conjunctivitis and diarrhea.
But the virus has been very rarely implicated in cases of hepatitis in people who have weakened immune systems, the CNN reported.
The WHO identified 74 cases of severe, acute hepatitis – inflammation of the liver – among children across the UK.
Three confirmed cases of acute hepatitis of unknown aetiology have been reported in children (age range 22-month-old to 13-year-old) in Spain, the agency said.
Health officials in the US state of Alabama said they have been investigating similar cases of hepatitis in children in the state since November, the CNN reported.
On April 5, the global health agency was notified of 10 cases of severe acute hepatitis of unknown aetiology in children under the age of 10 years, across central Scotland and by April 8, total 74 cases had been identified in the UK.
In addition, less than five cases (confirmed or possible) have also been reported in Ireland.
While the WHO excluded hepatitis viruses types A, B, C, E, D and E as the cause of liver disease in the UK.
The condition represented markedly elevated liver enzymes, often with jaundice, sometimes preceded by gastrointestinal symptoms, in children principally up to 10 years old.
Some cases also required transfer to specialist children’s liver units and six children have undergone liver transplantation.
However, no death has been reported in the UK till April 11, the WHO said.
The agency expects “more cases are likely to be reported in the coming days”.
The Alabama Department of Public Health reported nine children, ranging in age from 1 to 6, with hepatitis.
The most common causes of viral hepatitis identified were virus types A, B and C.
All the children were also positive for the adenovirus, and two needed liver transplants.
None of the children had any underlying health conditions, the department said.
“These children presented to providers in different areas of Alabama with symptoms of a gastrointestinal illness and varying degrees of liver injury including liver failure. Later analyses have revealed a possible association of this hepatitis with Adenovirus 41,” the statement said.
The WHO said the countries are conducting further investigations to identify the cause behind the condition.