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Scientists in the United Kingdom say they have identified the possible cause of an outbreak of a mysterious liver disease that has affected young children around the world.
New research suggests that not being exposed to two common viruses during the Covid-19 pandemic may increase children’s chances of severely ill with acute hepatitis.
In studies published on Tuesday, two research teams from University College London and the University of Glasgow said lockdown restrictions could result in some children losing early immunity to both adenovirus and newly associated virus 2 (AAV2).
Crucially, both groups said they found no evidence of a direct link between the sharp rise in hepatitis cases and infection with SARS-CoV-2, which causes Covid-19.
More than 1,000 children in 35 countries have developed an unknown type of severe acute hepatitis — or hepatitis — since the first case was reported in January.
The majority of cases were in children five years of age or younger, although diagnoses were discovered in children up to 16 years of age.
Adenovirus, which usually causes a mild cold or flu-like illness, was previously thought to be partly responsible for the mysterious outbreak, because it was the most common virus in samples from infected children.
However, the new research indicated that adeno-associated virus 2, which usually does not cause any disease and cannot reproduce without a “helper” virus such as adenovirus or herpes virus, was present in 96% of cases of unknown hepatitis examined in Both studies.
Researchers now say infection with the two viruses — AAV2 and adenovirus, or less commonly HHV6 — could provide the best explanation for the recent outbreak.
“While we still have some unanswered questions about the cause of this rise in acute hepatitis, we hope these findings reassure parents concerned about Covid-19 as neither team has found any direct link to SARS-CoV-2 infection,” Prof. Judith Brewer, UCL GOS Institute of Child Health, said in the report.
Children typically acquire—and become immune—to adenoviruses and other common diseases during the early childhood years. However, epidemiological limitations have greatly limited this early exposure.
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The findings add to theories among some health experts that the Covid lockdowns have reduced overall immunity to a number of common diseases. The researchers added that there is no link between coronavirus vaccines.
The two studies were conducted independently and simultaneously using samples from the United Kingdom. Dr. Sophia Morvopolo, a professor in the GOS Institute of Child Health at UCL, said more research is now needed to compare her findings with cases of acute hepatitis identified in other countries.
“International cooperation is now needed to further investigate and elucidate the role of AAV2 and co-virus in unexplained pediatric hepatitis in patients from different countries,” she said.