In several early studies, scientists found that many of the affected children were infected with adenoviruses, particularly adenovirus 41, which typically causes gastrointestinal symptoms. Adenoviruses are not typically known to cause hepatitis in otherwise healthy children, but they are common helper viruses for AAV2.
The new study was a collaboration among academic researchers, state health departments and the Centers for Disease Control and Prevention, among other institutions. The researchers studied biological samples from 16 American children, from six states, with unexplained hepatitis. All had previously tested positive for an adenovirus. They also studied samples from 113 control children, a group that included healthy children, children with gastroenteritis and children with hepatitis from a known cause.
Blood samples were available from 14 of the children with unexplained hepatitis. The researchers found AAV2 in 13 of those children, or 93 percent of them, compared with 3.5 percent of control children. Among the 30 children who had hepatitis linked to a known cause, none tested positive for AAV2.
Most of the children with unexplained hepatitis also tested positive for at least one herpes virus, which means that many were infected by at least three viruses: AAV2, an adenovirus and a herpes virus.
In the British studies, which were also small, scientists found AAV2 in the blood and livers of affected children. Many were also infected with an adenovirus or herpes virus. In one study, 25 of 27 affected children shared an immune-related genetic variant that is relatively uncommon in the general population. The finding suggests that this variant might predispose some children to hepatitis when they are infected by AAV2 and one or more helper viruses.
“It may turn out that in rare cases, you have kind of a perfect storm of events, where there’s a subset of children who were uniquely susceptible,” Dr. Chiu said.
More research is necessary to determine whether one or more of these viruses were injuring the liver directly, he said.
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