The CDC is still searching for the cause of mysterious liver illness in kids

The search for the cause behind the cluster of mysterious, severe hepatitis cases in young children continues.

Reports of potential cases have poured in since the Centers for Disease Control and Prevention issued a nationwide alert to physicians in April, asking them to be on the lookout for unexplained cases of liver inflammation in kids. 

Those cases haven’t led to any direct answers yet, but experts are confident that further research over the coming months will be fruitful. 

A total of 296 potential cases of unexplained hepatitis in young children have been identified so far, the CDC reported Friday. Most of the cases are not new; many were identified in retrospect, with doctors looking as far back as October. And while the number may sound high, they haven’t exceeded the expected yearly number of severe pediatric hepatitis cases.

In fact, cases have been falling in recent weeks, according to Dr. Markus Buchfellner, a pediatric infectious diseases fellow at the University of Alabama at Birmingham. Buchfellner first alerted the CDC to unusual back-to-back cases of pediatric hepatitis last year.

But falling case numbers don’t mean scientists are taking their eye off the ball. The situation is “still alarming enough that we need to know more about it,” he said.

Most cases were in children under 5 years old; the average age was 2, the CDC reported. Nearly 90% of the children required hospitalization, 6% needed a liver transplant, and 11 children died.

None of the children tested positive for any of the common causes of hepatitis, including the viruses that cause hepatitis A, B and C. Hepatitis refers to inflammation of the liver in general and can have hundreds of causes, including other viruses, toxins and food poisoning.

In 224 of the cases, patients received a test for an adenovirus infection — a virus that’s considered to be a prime suspect. Just under half, 45%, tested positive. 

Adenoviruses are common among children and can cause a range of symptoms, from colds to pink eye to vomiting and diarrhea. But they’re not a known cause of severe hepatitis in healthy children.

Adenovirus is known to cause hepatitis in immunocompromised children, said Dr. David Sugerman, a medical officer in the Division of Viral Diseases at the CDC and an author of the new report. But the recent spate of cases differs from cases in immunocompromised children in two ways, he said. First, they’re in children with healthy immune systems, and second, the virus was…