The Centers for Disease Control and Prevention is investigating a range of possible causes for the 180 cases of hepatitis in children reported over the past seven months in the United States.

Cases of acute liver inflammation have been reported in 36 states since October 2021, though just 7% occurred in the past two weeks, Jay Butler, the agency's deputy director for infectious diseases, said Friday. Some of the cases have been severe. There was an additional death recorded this week, bringing the total to six, while 15 of the patients required liver transplants. Nevertheless, the smattering of new cases does not constitute a “spike” or an “outbreak,” Butler said.


Researchers are combing hospital discharge records to pinpoint the cause of new cases. They have found a common thread among many cases — adenovirus 41, which is not typically a cause of hepatitis in otherwise healthy children. The causes of hepatitis in children are not always evident to scientists. Between 30% and 50% of cases are of unknown origin. They have also ruled out hepatitis viruses A, B, and C and several other conditions that typically cause hepatitis and liver infections.

“From the medical reports that we've analyzed so far, we have not found any common exposures or patterns,” Butler said. “While this [does] not absolutely rule out anything this early in the investigation, it does help us narrow our search as it gets us closer to what we can eliminate focus on further. At present, the leading hypothesis remains an important role for adenovirus 41.”

The United Kingdom and several European countries have reported upticks in mysterious hepatitis cases as well. The U.K. Health Security Agency reported Friday there had been 197 cases of hepatitis of unknown cause in children under 16 since Jan. 1, 2022. Of that total, 11 have received liver transplants, but no cases have been fatal.

The agency is also considering the uptick to be a result of better-than-normal reporting of new cases.

“We are working to better understand whether this is a true increase in the number of cases of hepatitis in children or an existing pattern that’s now been revealed due to the improvement in detecting cases,” Butler said. “Thus far, we have not been able to document an actual increase in the overall number of pediatric hepatitis cases.”


They have ruled out COVID-19 vaccines as a link to the cases, noting that most of them have occurred in children under 5, who are not eligible for the shots yet. Whether the cases are linked to COVID-19 infection remains unanswered, though. About 15% of the children who had hepatitis in the U.K. also had COVID-19. It is possible for a child who has not completely recovered from COVID-19 to become infected with adenovirus 41, sending their immune system into overdrive, which can damage the liver.

The CDC raised the alarm about hepatitis cases in children earlier this month when the agency published a report detailing nine severe cases in Alabama. Researchers in that instance ruled out COVID-19 as a cause, as none of the children diagnosed had a history of COVID-19 infection or vaccination, and all lived in separate parts of the state, suggesting the cases were unrelated.