A dangerous, liver-compromising virus is spreading among kids in the US.

On Thursday, the Centers for Disease Control and Prevention (CDC) issued an alert to healthcare providers, warning that a "cluster" of at least nine unusual pediatric hepatitis cases have been spotted in Alabama in recent months, and there could be more out there nationwide.

The CDC said these cases of liver inflammation appear to have been caused by an adenovirus, not COVID-19.

The first US cases were identified in October 2021 at a "large children's hospital" in Alabama, the CDC said. By November, five of the patients there had suffered "significant" liver injury, and three of them had acute liver failure. Two patients required liver transplants, though none died.

Similar cases were reported in the UK earlier this month, and the World Health Organization said last week that there have been others spotted in Spain and Ireland. The CDC told Stat last week that the US cases are in kids ranging in age from 1 to 6 years old, and the Alabama health department said in a release on April 14 that the children infected were all under 10 years old.

A respiratory adenovirus at work?

The culprit behind the cases of liver inflammation seems to be a pathogen called adenovirus 41, a virus that spreads (like COVID does) through close contact, and respiratory excretions. Adenoviruses can also spread through stool, making hand-washing important.

The children with this hepatitis were all previously healthy, and did not have COVID-19, the health agency said. That is puzzling, because adenovirus 41 typically only infects immunocompromised children, and is "not known to be a cause of hepatitis in otherwise healthy children," according to the CDC. There is no treatment for the illness.

Adenovirus 41 often causes pediatric acute gastroenteritis, with symptoms including:

  • diarrhea,
  • vomiting,
  • fever,
  • as well as respiratory symptoms.

For now, the CDC is recommending that medical providers test kids with unusual, inexplicable hepatitis cases for the adenovirus, using PCR tests.

This article was originally published by Business Insider.

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