The number of cases of hepatitis in children has increased in the past year without the cause being clear. Now researchers present new findings.
A previously undetected virus and other factors may be to blame for an increase in unexplained cases of hepatitis in young children worldwide. This is independently suggested by three studies in the journal “Nature”. The return of children to daycare centers and schools after the corona lockdowns can also play a role.
In early April 2022, mysterious and sometimes serious cases of hepatitis – an inflammation of the liver – occurred in previously healthy children in whom no hepatitis viruses could be detected. In July, the World Health Authority (WHO) reported more than 1,000 sick children in 35 countries, and not a single case from Germany was included in the corresponding list. About 50 of the patients, some of whom were very young, required a liver transplant and at least 22 died.
The now published studies from Great Britain and the US suggest a link with the adeno-associated virus 2 (AAV2): The research groups led by the University of Glasgow, University College London and the University of California found it in blood and liver tissue samples from children partly high concentrations of the virus.
Until now, it was assumed that AAV2 did not cause disease. In addition, AAV2 itself cannot infect cells: it needs other viruses to multiply.
The University College London team even found small traces of a human adenovirus and a herpes virus in addition to AAV2, which could act as “helper viruses”. The scientists suspect these cause AAV2 to multiply and contribute to the severity of liver damage.
The researchers at the University of California also saw so-called co-infections in all sick children, in this case the Epstein-Barr virus or a herpes virus. “We were surprised that the infections we found in these children were not caused by an unusual emerging virus, but by common childhood viral pathogens,” Charles Chiu, lead author of the US study, said in a statement.
“All three studies make the same observation of AAV2 in children with unexplained acute hepatitis,” summarizes Frank Tacke of the Berlin Charité in an accompanying commentary. The fact that the studies were conducted on two continents makes them even more valuable given the global nature of the outbreak. However, all studies were performed retrospectively and included only a relatively small number of cases and an even smaller number of available liver tissue samples. To reveal possible factors or cofactors for the onset of the disease, more clinical information about the sick children is also needed.
The study authors themselves stress that their work would link AAV2 to the recent increase in unexplained cases of hepatitis. However, it remains unclear what role the virus plays in causing liver inflammation. According to Tacke, targeted and controlled follow-up studies would be needed here. He writes, “Direct evidence on how AAV2 might cause hepatitis is limited.”
Genetic analyzes by the Glasgow research group suggest that an abnormal immune response due to the corresponding hereditary factors could be the cause of hepatitis – and not a direct liver-damaging effect of AAV2. The scientists found that 93 percent of the affected children carried a gene variant that indicates a susceptibility to autoimmune diseases involving immune cells called T cells. The London researchers also found evidence of an immune-mediated process when they compared liver samples from patients and healthy controls.
In his comments, however, Frank Tacke does not rule out the possibility that the coronavirus may also be important: a direct involvement of SARS-CoV-2 cannot be ruled out and an indirect effect is also conceivable. The hepatitis wave started in the spring of 2022 with the relaxation of COVID-19 measures around the world. “The timing of the outbreak could be explained by the fact that after the closures, the children were suddenly exposed to a deluge of viruses or had poorly developed immune systems, leading to an increased susceptibility to otherwise harmless viruses.”
A suspicion also expressed by Charles Chiu, lead author of the US study: “It could be an unintended consequence of what we have experienced in the past two to three years of the pandemic.” Meanwhile, the incidence of acute severe hepatitis in children has decreased. The best way to continue to protect them from this is to wash their hands regularly and keep them home when they are sick. (sda/dpa)
Source: Blick
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