One child has died and more than a dozen have undergone liver transplants as a result of a mysterious outbreak of severe acute hepatitis that's sickened children in the U.K., the U.S. and 10 other countries, the World Health Organization said.
Health authorities are trying to determine the source of the liver-inflaming disease that's afflicted at least 169 children, ages 1 month to 16 years, as of April 21, the WHO said in a statement Saturday. Typical causes of viral hepatitis have been excluded.
The United Nations agency was notified on April 5 of 10 cases among previously healthy children across central Scotland with jaundice, diarrhoea, vomiting and abdominal pain. Three days later, 74 cases had been identified in the U.K.
As of April 21, the U.K. had 114 cases followed by 13 in Spain, 12 in Israel, nine in the U.S. and 21 more scattered among Denmark, Ireland, the Netherlands, Italy, Norway, France, Romania and Belgium. Many were infected with a strain of adenovirus, a family of viruses that cause a range of illnesses including the common cold.
"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. "While adenovirus is a possible hypothesis, investigations are ongoing for the causative agent."
Seventeen children, or about 10 per cent of cases, have required a liver transplant and at least one death has been reported, the Geneva-based agency said. With more extensive searching, it's "very likely that more cases will be detected before the cause can be confirmed and more specific control and prevention measures can be implemented," it said.
Symptoms include liver inflammation, with markedly high liver enzymes, and jaundice, preceded by abdominal pain, diarrhoea and vomiting. The common viruses that cause acute viral hepatitis -- hepatitis viruses A, B, C, D and E -- haven't been detected in any of the cases, WHO said.
International travel or links to other countries haven't revealed any clues yet either. Toxicology and additional microbiological testing is underway in affected countries, which have also initiated enhanced surveillance activities.
Adenovirus was detected in more than 40 per cent of cases. Of virus samples that underwent molecular testing, 18 were identified as F type 41, WHO said. Nineteen cases were found to have a SARS-CoV-2 and adenovirus co-infection.
"Due to enhanced laboratory testing for adenovirus, this could represent the identification of an existing rare outcome occurring at levels not previously detected that is now being recognized due to increased testing," the agency said.
More than 50 types of adenoviruses can cause infections in humans, according to the WHO. Usually a cause of self-limited communicable infections, they most commonly cause respiratory illness. Depending on the type, they can also cause other illnesses such as gastroenteritis, conjunctivitis and bladder infection.
Adenovirus type 41, the strain implicated in the liver-disease outbreak, typically causes diarrhoea, vomiting, and fever, often accompanied by respiratory symptoms. Even though adenovirus is being investigated as a possible cause of the outbreak, it doesn't fully explain the severity of the symptoms, WHO said.
"While there have been case reports of hepatitis in immunocompromised children with adenovirus infection, adenovirus type 41 is not known to be a cause of hepatitis in otherwise healthy children," it said.
