Viral infections and genetic variant are linked to cases of hepatitis in children

Some of the children were infected with adeno-associated virus 2 and shared a relatively rare genetic variant, according to two small studies.

A complex combination of factors may be responsible for the pediatric hepatitis cases that have puzzled doctors in recent months, according to two new small studies.

The studies are based on only a few dozen cases and have not yet been peer-reviewed or published in scientific journals. Yet they suggest that children who developed severe, unexplained cases of liver inflammation may have been simultaneously infected with two different viruses, including one known as adeno-associated virus 2 (A.A.V.2), a virus usually benign that requires a second "helper" virus in order to replicate.

Adenoviruses, which have already been found in many children with the mysterious hepatitis reported during of the past year, are common helper viruses for A.A.V.2.

Many of the children studied also had a relatively rare version of a gene that plays an important role in the immune response, the scientists found.

Together, the results suggest a possible explanation for the cases of hepatitis: in a small subset of children who carry this variant particular genetics, double infections by A.A.V.2. and a helper virus, often an adenovirus, trigger an abnormal immune response that damages the liver.

Still, the researchers acknowledged that the studies are based on a small number of children in a single region of the world (the United Kingdom) and that a causal link had not been proven.

"There are still many things we don't know," said Dr Antonia Ho, clinical lecturer at the MRC-University of Glasgow Center for Virus Research and author of one of the new studies.

But, she added: "We felt - because there have been very few answers about the causes - that we should publish these findings so that other people can start researching the cause. 'A.A.V.2. and study this further."

The results are intriguing but preliminary, said Dr. Saul Karpen, pediatric hepatologist atric at Emory University and at Children's Healthcare of Atlanta, who was not involved in the research. "It's not a definitive study," he said. "Thematically this can certainly make sense, but there is no full support for this."

Cases of pediatric hepatitis are extremely rare but can be serious. As of July 8, 1,010 probable cases had been reported in 35 countries, according to the World Health Organization. Five percent of these children required a liver transplant and 2% died.

Several preliminary studies have revealed that many children are infected with adenovirus , one of the common group of viruses that usually cause cold or flu symptoms. The new studies suggest that if adenoviruses are involved in cases of hepatitis, they might just be history.

In one of the new studies, scientists compared nine Scottish children with unexplained hepatitis to 58 children in control groups. The researchers used genomic sequencing to identify all of the viruses present in the children's blood, liver and other samples.

Scientists found the adeno- associated 2 in the blood of the nine affected children and in liver samples from the four children for whom such samples were available...