Health officials in several countries are investigating mysterious cases of severe liver disease in children, and they think it may be related to a kind of virus usually associated with colds.

The U.K. has been investigating at least 74 cases in which children came down with hepatitis, or liver inflammation, the World Health Organization said Friday. Three similar cases in Spain and a few in Ireland are being investigated, the WHO said.

Meanwhile, U.S. health officials say they are looking into nine similar cases. All were in Alabama, but officials say they are looking to see if there are more elsewhere.

“Given the increase in cases reported over the past one month and enhanced case search activities, more cases are likely to be reported in the coming days,” WHO officials said in a statement.

The U.S. children ranged in age from 1 to 6 years old, and two required liver transplants. The European cases are in a similar age range, though some have been older, WHO officials said.

The WHO first became aware of the unusual illnesses early this month, when they learned of 10 children in Scotland with liver problems. One got sick in January and the nine others in March. All became severely ill and were diagnosed with hepatitis after being taken to the hospital.

The liver processes nutrients, filters the blood and fights infections. The infections caused symptoms like jaundice, diarrhea and abdominal pain. Hepatitis can be life-threatening if left untreated.

Since then, British health officials have identified at least 64 more cases. None died, but six needed liver transplants, the WHO said Friday.

Laboratory testing has ruled out the hepatitis type A, B, C and E viruses that usually cause such illnesses. Officials say they are not aware of international travel or other factors that might have put the kids at risk.

But they noted there’s been a recent surge in the spread of adenoviruses.

There are dozens of adenoviruses, many of them associated with cold-like symptoms, fever, sore throat and pink eye. But some versions can trigger other problems, including inflammation in the stomach and intestines.

Adenoviruses previously have been linked to hepatitis in children, but mostly in kids with weakened immune systems.

Some of the European children tested positive for adenovirus, and some tested positive for COVID-19. But more lab work is needed to explore any potential associations with specific viruses, the WHO said.

Alabama health officials say they have been looking into an increase in hepatitis in children since November. In each case, the child tested positive for adenovirus. Officials are exploring a link to one particular version—adenovirus 41—that’s normally associated with gut inflammation.

None of the Alabama cases had any underlying health conditions that would seem to put them at risk for liver illness, health officials said.

“At this time adenovirus may be the cause for these, but investigators are still learning more—including ruling out the more common causes of hepatitis,” the CDC said in a statement.

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