More than 1,000 children in 35 countries have developed an unidentified type of severe acute hepatitis (or inflammation of the liver) since the first case was reported in January 2022.
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UK scientists say they have identified the likely cause of a recent outbreak of a mysterious liver disease affecting young children around the world.
Lack of exposure to two common viruses during the Covid-19 pandemic may have increased the chances of children becoming seriously ill with acute hepatitis, new research suggests.
In studies published on Tuesday, two research teams from University College London and the University of Glasgow said lockdown restrictions may have caused some babies to lose early immunity to both adenovirus and the newly linked adeno-associated virus 2 (AAV2).
Crucially, both teams said they found no evidence of a direct link between the rise in hepatitis cases and infection with SARS-CoV-2, the cause of Covid-19.
Virus co-infection
More than 1,000 children in 35 countries have developed an unidentified type of severe acute hepatitis (or inflammation of the liver) since the first case was reported in January.
The majority of cases have been in children five years of age or younger, although diagnoses have been detected in children as young as 16.
Adenovirus, which usually causes a mild cold or flu-like illness, was previously believed to be partly responsible for the mysterious outbreak, as it was the virus most commonly found in samples from affected children.
However, the new research indicated that adeno-associated virus 2, which normally does not cause disease and cannot replicate without a “helper” virus such as adenovirus or herpesvirus, was present in 96% of hepatitis cases unknown examined in both studies.
A mystery solved?
Researchers now say that coinfection with the two viruses — AAV2 and an adenovirus, or less commonly the herpesvirus HHV6 — may offer the best explanation for the recent outbreak.
“While we still have some unanswered questions about what exactly caused this increase in acute hepatitis, we hope these results can reassure parents concerned about Covid-19, as neither team has found a direct link with SARS-CoV-2 infection,” Professor Judith. Breuer, from the UCL Institute of Child Health GOS, said in the report.
Children typically gain exposure and immunity to adenovirus and other common diseases during early childhood. However, pandemic restrictions largely limited this early exposure.
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The findings add to theories among some health experts that the Covid lockdowns have reduced public immunity to several common diseases. The researchers added that there was no link to the coronavirus vaccines.
The two studies were conducted independently and simultaneously using UK samples. Dr Sofia Morfopoulou, a professor at UCL’s GOS Institute of Child Health, said more research was now needed to compare their findings with cases of acute hepatitis identified in other countries.
“International collaborations are now needed to investigate and elucidate the role of AAV2 and virus coinfection in unexplained pediatric hepatitis in patients from different countries,” he said.