A severe outbreak of hepatitis that caused liver damage in children in their teens could be due to an adenovirus virus infection. Officials from the World Health Organization said Thursday that although hepatitis was not initially suspected, further investigations are needed.

Eleven countries have reported cases of acute severe hepatitis, which includes the United States, in at least 169 children aged 1-month-to-16-years old. The largest epidemic was in the U.K. according to the latest WHO report. At least 17 children were required to have liver transplants. One patient died.

Hepatitis refers to inflammation of the liver that is most often caused by viruses. However, medications and other toxins may also be a trigger for the condition.

“What’s particularly remarkable is that most of these children were once healthy,” said Dr. Philippa Easterbrook (a WHO official who monitors Hepatitis) during an interactive question-and-answer session streamed live on Thursday by the global health agency’s Twitter.

Adenovirus has been confirmed in at least 74 out of the children. according to the WHO. Adenoviruses, which are often associated with respiratory disease, can also cause stomach and pinkeye problems and bladder infections. According to WHO, the WHO has seen an increase in adenovirus transmission in the U.K. due to severe hepatitis in children.

Easterbrook stated that while this does not prove a causal connection between these cases at the moment, it was a promising early signal and is currently being examined in greater detail.

In rare cases, Adenovirus may have been linked to hepatitis in children who are immune-suppressed, says Dr. Richard Peabody. He is the WHO Europe high-threat pathogens leader. The WHO states that adenovirus does not cause hepatitis among healthy children.

WHO data shows that at least 20 children were diagnosed with Covid. Twenty-eight of these children also tested positive for adenovirus and Covid. Peabody suggested that Covid could also be a factor in the outbreak of hepatitis. However, it is not certain and further investigation is required.

The WHO was first informed by the U.K. about severe acute liver disease in children. According to WHO data, liver inflammation and nausea are the most frequent symptoms.

This week the Centers for Disease Control and Prevention reported that they had received a report from them issued a nationwide health alertWe found nine cases in Alabama of hepatitis among children aged 1-6 years old. According to the CDC, all nine cases of hepatitis were caused by liver damage and some suffered from liver failure. The CDC suspects that adenovirus is the culprit, although the public-health agency says investigations are ongoing.

Easterbrook reported that officials from the health sector have mostly ruled out the possible causes of the symptoms, which could include hepatitis A or B virus, C virus, D virus, and E viruses. The WHO has confirmed that no cases of hepatitis A, B, C or D have been reported. Easterbrook also said that Epstein Barr and CMV viruses don’t appear responsible. She said that parents have so far not reported any common exposure to drugs, toxins, or food.

Easterbrook explained that Covid-19 vaccination has been largely eliminated by the WHO as a cause of autism, mainly because the WHO believes the vaccine was not administered to the majority.