Researchers are investigating a possible connection between children infected with hepatitis and adenoviruses and liver damage in children.

The Centers for Disease Control and Prevention advised physicians and public health officials Thursday to be on the lookout for pediatric patients with hepatitis from unknown causes. According to the advisory, a cluster of kids in an Alabama children's hospital developed liver damage — liver failure in some cases – in conjunction with hepatitis and adenovirus infections.

Nine children were identified between October 2021 and February 2022, all of whom tested positive for adenoviruses, which cause cold-like symptoms: diarrhea; sore throat; fever; and can lead to conjunctivitis, bronchitis and pneumonia.

Every patient also tested positive for hepatitis, inflammation of the liver that can lead to not just liver damage and, in the worst cases, even death. And though none of the patients died due to their ailments, two required liver transplants.

In light of these findings, the CDC is advising healthcare professionals to test for adenoviruses in pediatric patients diagnosed with hepatitis from unknown causes.

The World Health Organization was notified about similar cases in the United Kingdom earlier this month. Seventy-four cases of acute severe hepatitis with unknown etiologies were identified in the U.K. The patients tested negative for hepatitis A, B, C, D and E, however, some of the children tested positive for SARS-CoV-2 and adenoviruses.

Similar to cases in the U.S., there have been no child deaths, but six did require liver transplants.

"Overall, the [etiology] of the current hepatitis cases is still considered unknown and remains under active investigation," a WHO news release said. "Laboratory testing for additional infections, chemicals and toxins is underway for the identified cases."

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