More than 1,000 children in 35 countries have developed an unidentified type of severe acute hepatitis — or liver inflammation — since the first case was reported in the January 2022.
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Scientists in the U.K. say they have identified the likely cause of a recent outbreak of mysterious liver disease afflicting young children around the world.
New research suggests that a lack of exposure to two common viruses during the Covid-19 pandemic may have increased the chances of children becoming severely ill with acute hepatitis.
In studies published Tuesday, two research teams from University College London and the University of Glasgow said that lockdown restrictions could have led some infants to miss out on 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 spike in hepatitis cases and SARS-CoV-2 infection, the cause of Covid-19.
More than 1,000 children in 35 countries have developed an unidentified type of severe acute hepatitis — or liver inflammation — since the first case was reported in January.
The majority of cases have been in children aged five years old or younger, though diagnoses have been detected in children aged up to 16 years.
Adenovirus, which typically causes mild cold or flu-like illness, was previously believed to be partly responsible for the mysterious outbreak, as it was the most commonly found virus in samples from affected children.
However, the new research indicated that adeno-associated virus 2, which normally causes no illness and cannot replicate without a “helper” virus such as adenovirus or herpesvirus, was present in 96% of cases of unknown hepatitis examined across both studies.
Researchers now say that coinfection with the two viruses — AAV2 and an adenovirus, or less commonly the herpesvirus HHV6 — could offer the best explanation for the recent outbreak.
“While we still have some unanswered questions about exactly what led to this spike in acute hepatitis, we hope these results can reassure parents concerned about Covid-19 as neither teams have found any direct link with SARS-CoV-2 infection,” Professor Judith Breuer, UCL GOS Institute of Child Health, said in the report.
Typically, children gain exposure — and immunity — to adenoviruses and other common illnesses during their early childhood years. However, pandemic restrictions largely limited that early exposure.
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The findings add to theories among some health experts that Covid lockdowns have reduced public immunity to a number of common illnesses. The researchers added there was no link to coronavirus vaccines.
The two studies were conducted independently and simultaneously using U.K. samples. Dr. Sofia Morfopoulou, professor at UCL’s GOS Institute of Child Health, said further research was now needed to compare their findings with cases of acute hepatitis identified in other countries.
“International collaborations to further investigate and elucidate the role of AAV2 and co-infecting viruses in pediatric unexplained hepatitis in patients from different countries are now needed,” she said.