Scientists believe they have found the most likely cause of mysterious and sometimes deadly cases of hepatitis in young children, leading them to mothball COVID-19 as a possible theory.
A new virus has been identified in 96 percent of cases analyzed in two separate studies: one in Scotland and another across the U.K. That compared with just 4 percent detected across multiple control cases.
Scientists believe that infection with this virus, called adeno-associated virus 2 infection (a member of the parvovirus family) has somehow caused these unusual clusters of cases: either through co-infection with another virus or possibly alone.
But they all but rule out COVID-19 as a cause. “It is extremely unlikely that this is related to COVID-19,” said Emma Thomson, senior author of the Scottish study, during a journalists’ briefing.
She said that around two-thirds of the children studied had antibodies to coronavirus — a similar level to the general population due to prior infection. And the fact that hepatitis cases are appearing two years after the start of the pandemic also does not align with a COVID theory, she said.
As of July 12, there have been over 1,000 cases of unexplained hepatitis from 35 countries involving 22 deaths. In the U.K. no deaths have been recorded, while 12 children have required liver transplants.
Adeno-associated virus 2 infection, or AAV2, infects most people by the time they are aged 10, but it is not normally associated with human disease, said Thomson, a clinical professor and consultant in infectious diseases at the MRC-University of Glasgow Centre for Virus Research.
In addition, AAV2 requires infection with another virus, known as a “helper virus” to be able to replicate, Thomson said.
With the surge in mystery hepatitis cases peaking around two weeks after a big spike in adenovirus cases, scientists believe this coinfection may be the cause. In the studies, 86 percent of the children had adenovirus infection. A small number also had herpes virus infection.
In addition, the Scottish study found a possible genetic risk factor, with 17 out of 20 cases studied having a specific gene (DRB1 04:01), much higher than the population level of 16 percent. This gene could identify those most susceptible, but more research is needed.
The scientists — from the University of Glasgow, Great Ormond Street Hospital and the University College London Great Ormond Street Institute of Child Health — have called for further international studies to confirm their hypotheses.
Both studies are now available as pre-prints and have not been peer reviewed.