Health officials from around the world are trying to figure out why children are being stricken by acute cases of hepatitis – a disease of the liver.

The World Health Organization reported on Saturday that as of April 21, 2022, “at least 169 cases of acute hepatitis of unknown origin have been reported from 11 countries.”

The children ranged in age from 1 month to 16 years. Seventeen of them needed a liver transplant and one child died.

WHO said cases have been reported in the United Kingdom of Great Britain and Northern Ireland (114), Spain (13), Israel (12), the United States of America (9), Denmark (6), Ireland (<5), The Netherlands (4), Italy (4), Norway (2), France (2), Romania (1), and Belgium (1).

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

WHO said it has not been determined if there is a link between the cases.

Last week, the U.S. Centers for Disease Control and Prevention issued a health advisory to health care providers and public health officials recommending they test for adenovirus in children who have hepatitis but the cause is not known.

The CDC said that in November it was notified of five pediatric patients in Alabama “with significant liver injury, including three with acute liver failure, who also tested positive for adenovirus. All children were previously healthy. None had COVID-19.”

“A possible association between pediatric hepatitis and adenovirus infection is currently under investigation,” the CDC said.

According to the CDC, “Hepatitis is inflammation of the liver that can be caused by viral infections, alcohol use, toxins, medications, and certain other medical conditions. In the United States, the most common causes of viral hepatitis are hepatitis A, hepatitis B, and hepatitis C viruses.

Signs and symptoms of hepatitis include fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain, dark urine, light-colored stools, joint pain and jaundice.

“Adenoviruses are viruses that spread by close personal contact, respiratory droplets, and fomites. There are more than 50 types of immunologically distinct adenoviruses that can cause infections in humans.

Adenoviruses most commonly cause respiratory illness but depending on the adenovirus type they can cause other illnesses such as gastroenteritis, conjunctivitis, cystitis, and, less commonly, neurological disease. There is no specific treatment for adenovirus infections.

Adenovirus type 41 commonly causes pediatric acute gastroenteritis, which typically presents as diarrhea, vomiting, and fever; it can often be accompanied by respiratory symptoms.

While there have been case reports of hepatitis in immunocompromised children with adenovirus type 41 infection, adenovirus type 41 is not known to be a cause of hepatitis in otherwise healthy children.”