NBC News: Amid fresh clues about severe hepatitis in kids, researchers ask: Is the phenomenon new at all?

A new theory suggests that a co-infection of two viruses, plus a genetic marker, could be behind cases of dangerous liver inflammation among children.

Until recently, a prevailing theory about the severe hepatitis cases popping up in children suggested that an adenovirus was probably to blame.

Since April, many young kids with dangerous liver inflammation have tested positive for adenovirus 41, which typically causes coldlike illness or an upset stomach. But two studies released this month, which have not yet been peer-reviewed, outlined another theory: Some children may have been infected with an adeno-associated virus, which uses a second helper virus to replicate.

Researchers from Scotland and England detected one particular adeno-associated virus, called AAV2, in the blood and livers of U.K. children with severe hepatitis. The researchers suggested that some kids may have been co-infected with AAV2 and another virus like adenovirus 41 — a combination that could result in liver failure. The studies also identified a genetic marker that might put children at higher risk of this outcome.

...Lishan Su, who directs the virology, pathogenesis and cancer division at the University of Maryland School of Medicine's Institute of Human Virology, said it's plausible that a combination of two viruses and a unique genetic marker would lead to liver inflammation.

Both studies found the AAV2 adeno-associated virus in nearly all blood and liver samples from children with mysterious hepatitis cases. And the study from Scotland did not find AAV2 in any blood samples from healthy kids or those admitted to the hospital for hepatitis with a known origin.

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