A chain of events possibly triggered by unrecognized infection with the SARS-CoV-2 coronavirus could be causing the mysterious cases of severe hepatitis reported in hundreds of young children around the world, researchers suggest.

Children with COVID-19 are at significantly increased risk for liver dysfunction afterward, according to a report posted on Saturday on medRxiv ahead of peer review. But most of the children with acute hepatitis - which is generally rare in that age group - do not report a previous SARS-CoV-2 infection. Instead, the majority have been found to be infected with an adenovirus called 41F, which is not known to attack the liver. It is possible that the affected children, many of whom are too young to be vaccinated, may have had mild or asymptomatic COVID infections that went unnoticed, a separate team of researchers suggest in The Lancet Gastroenterology & Hepatology. If that were true, they theorize, then lingering particles of the coronavirus in the gastrointestinal tract in these children could be priming the immune system to over-react to adenovirus-41F with high amounts of inflammatory proteins that ultimately damage the liver.

"We suggest that children with acute hepatitis be investigated for SARS-CoV-2 persistence in stool" and for other signals that the liver damage is happening because the spike protein of the coronavirus is a "superantigen" that over-sensitizes the immune system, they said.