Last year, health specialists all across the globe were baffled by reports of severe, inexplicable hepatitis in otherwise healthy youngsters.
Since it needs a second “helper” virus in order to proliferate, AAV2 is not often connected with illness. Several helper viruses were detected in the systems of many of the youngsters with mysterious cases of hepatitis or liver inflammation.
The timing of the epidemic may have been connected to the relaxation of pandemic measures, which exposed many young infants for the first time to common viruses.
Dr. Charles Chiu, an infectious disease expert and microbiologist at the University of California, San Francisco and lead author of the current research, speculated that this might have created a population particularly susceptible to contracting several viral diseases.
This study was published in Nature on Thursday, alongside two others from the United Kingdom that found similar evidence linking AAV2 to hepatitis. The preliminary British research was published online last summer.
Dr. Frank Tacke, chairman of the gastrointestinal and hepatology department at the Charité University Medical Center in Berlin, who was not involved in the research but authored a commentary accompanying the study, called the consistent results “very astonishing.” The fact that three separate organisations discovered the same thing in various parts of the globe lends credence to the findings.
Dr. Tacke cautioned that the results should not be taken as proof that AAV2 causes hepatitis or is “simply a bystander” in the disease’s progression.
The incidents began in the autumn of 2021, but specialists say they spiked in the spring and summer of last year before gradually dying down. As of late July, the World Health Organization has received reports of over a thousand possible cases from 35 nations, including the United States. Around 5% of kids needed a liver transplant, and 2% of them didn’t make it.
Adenoviruses, and in particular adenovirus 41, which is known to produce gastrointestinal symptoms, were discovered to be present in large numbers among the afflicted children in numerous early investigations. While adenoviruses are often used as helper viruses for AAV2, they are not normally known to induce hepatitis in otherwise healthy youngsters.
Researchers from many universities and organisations (including state health agencies and the CDC) worked together on the new study. The investigation looked at biological samples from 16 kids with hepatitis in six different locations throughout the United States. All of them had a history of positive adenovirus testing. Samples from 113 healthy children, children with gastroenteritis, and children with idiopathic hepatitis were also analysed.
Fourteen of the children with mysterious hepatitis had blood samples accessible for analysis. Thirteen of the children (93%) tested positive for AAV2, whereas just 3.5% of the control group did. None of the 30 kids with endemic hepatitis from a recognised source had AAV2 in their systems.
Children with unexplained hepatitis were more likely to be infected with AAV2, adenoviruses, and herpes viruses than children with other types of hepatitis.
Researchers in Britain also detected AAV2 in the blood and livers of afflicted youngsters, albeit their investigations were much smaller. Adenovirus and herpes virus infections were also common. In one investigation, a rare genetic variation associated with the immune system was found to be present in 25 of 27 afflicted children. This discovery raises the possibility that infection with AAV2 and a helper virus makes certain youngsters more susceptible to developing hepatitis.
For certain youngsters, “it may turn out that in rare circumstances, you have sort of a perfect storm of events,” Dr. Chiu said.
He added additional study was needed to discover whether any of these viruses were directly damaging the liver.
In certain youngsters, a robust immune response brought on by infection with several viruses may be to blame for the liver damage they experience.
Dr. Tacke emphasised that identifying the process was crucial because of the therapy implications it would have. Antivirals may be the best option if viruses are responsible for liver damage; steroids may be more effective if an overactive immune system is to blame.