Scientists have found the culprit behind a mysterious hepatitis outbreak in children -Health

Several groups of scientists believe they have uncovered a possible cause of A mysterious wave Severe hepatitis last year that hospitalized and killed children around the world. in three In research published this week, the groups detailed evidence that a common but not usually pathogenic virus was strongly linked to cases, possibly aided by co-infection with other common viruses. Affected children may also be genetically unlucky.

At the beginning of last year, the health officer of the United Kingdom Dr First report on a Cluster of severe hepatitis, with cases in fall 2021. In severe cases, it can directly lead to liver failure or death. These children did not test positive for any known cause of hepatitis, including the group of unrelated viruses that named the condition.

Before long, other places will report Similar clusters. By July 2022, accordingly World Health OrganizationMore than 1,000 cases of this severe, unexplained childhood hepatitis have been documented in 35 countries. Most children were hospitalized; About 5% become so ill that they need a liver transplant; And 2% eventually die as a result.

There are various theories about the origin of these clusters. Many, but not all, children test positive for adenovirus, a common pathogen that can cause illness; Some recently had SARS-CoV-2, the cause of Covid-19. But the damage caused by these viruses was not usually associated with the severe liver damage seen in these children, indicating that some other catalyst was at play. A debunked theory blamed the Covid-19 vaccine, but Many are affected The children were very young shot received.

inside three the papers published This week in Nature, an independent team of scientists described Evidence points to a common suspect, though it hasn’t worked alone: ​​adeno-associated virus type 2 (AAV-2). Each group found that most of the cases they studied were recently infected with AAV-2, and at much higher rates than similarly matched control patients or patients who had developed hepatitis for known reasons. Some groups have found signs of AAV-2 infecting children’s livers and indirect evidence that the organ was damaged as a result.

AAV-2 is peculiar, even in The virus is a satellite virus, meaning that it can only replicate inside a cell when another “helper” virus infects the same cell. As the name suggests, adenoviruses are a common helper virus for AAV-2, but herpesviruses can also be partners. In many of these children, scientists have also found these helper viruses, and sometimes even more than one.

AAV-2 isolated from infected individuals The children do not appear to differ genetically in any significant way from other known strains, but a study by researchers in the UK advises Another key reason behind the clusters: most of them carry the same variant of a gene that affects our immune system, and at a higher rate than the general population. It’s possible that carrying this variant makes children less likely to develop hepatitis in conditions that make them more vulnerable, the authors said.

“It may turn out that in rare cases, you have a perfect storm of events, where there is a subset of children who were uniquely susceptible,” said Charles Chew, an infectious disease specialist at the University of California, San Francisco. The authors behind the study looked at US children, to say The New York Times.

These studies are not alone Evidence that AAV-2 is responsible for clusters. For one, they are all based on a small sample of patients and from only two countries where cases have been reported (USA and US).who) there Exactly how AAV-2 might do this to children remains unansweredAnd we also don’t know why these clusters arose when.

It is possible that the relative lack of other common infections during the early years of the epidemic led to an immunological lag, such that the prevalence of these diseases (and their rare complications) was temporarily greater than usual when people began to socialize regularly again. Still data from the United States pointed out The documented rate of unexplained hepatitis cases among children did not increase last year from its pre-pandemic baseline. In other words, AAV-2 can always be one Rare but consistent cause hepatitis, but we only noticed it now because we were finally looking for it. It is also possible that some countries experienced a real surge last year, while others did not.

Fortunately, the reported incidence of these unexplained hepatitis cases has decreased significantly since 1991 Last summer peaked, so the immediate crisis seemed over. But more research is needed to confirm what these scientists found, as well as to better understand what exactly happened to these children and whether we can do anything to prevent or reduce similar risks. Future cases.