WHO’s Dr. Philippa Easterbrook gives a situation update on the recent hepatitis outbreak affecting children including possible causes and steps parents, caregivers and countries should take.

According to her, the first cases of severe acute hepatitis, that means inflammation of the liver in previously healthy young children were reported from Scotland in early April this year.

And from that time, over the last four months, more than a thousand cases have been reported from 35 countries worldwide. The majority of these cases are in young children aged less than five years and most present with the typical symptoms of acute gastroenteritis, so abdominal pain, nausea and vomiting. But then with rapid progression to jaundice indicating liver damage. That’s shown by pale stools, dark urine and yellowing of the skin or the eyes. A distinctive feature of this event has been the rapid progression  and the severity of the liver disease in previously healthy children.

Around a third have required intensive care support, 48 — that’s around 5% needed an urgent liver transplant for acute liver failure. And that’s a life changing event. 18 children, that’s around 2.5%, died.

What was unusual about this event is that we didn’t know the underlying cause. So one of the first priorities for WHO was to work with countries and partners to establish a cause. And early on some of these underlying causes were excluded through investigations of the affected children.

First, that none of the children were infected with the viruses that commonly cause hepatitis, so — hepatitis A, hepatitis B, C or E.

Secondly, that there was no evidence for a common exposure to foods or water, or to medications or other household members.

And thirdly, and importantly, there was no evidence for a link to COVID vaccination.

Since almost none of the affected children had been vaccinated. But there was an early clue that a common virus called adenovirus may have a role either acting alone or as a co-infection with another virus such as COVID either past or current COVID infection.

So we now have a much better picture and understanding. Around half to three quarters of all the affected children in those who had blood tests or blood samples available and that were tested were positive for adenovirus.

Touching on why a common virus like adenovirus caused such severe disease? And what are the signs that parents, caregivers, and countries should be looking for, Dr. Philippa Easterbrook said they don’t know for certain, but there are 2 likely explanations. 

First, that the young children had become more susceptible and sensitive to adenovirus. 

And this might be because over the two years that there had been public health measures for COVID in place, such as mask-wearing or closures of schools, there had been much less exposure among these children to many infections including adenovirus. When these measures were lifted, that’s in early this year, there was then an increase of the circulation and transmission of these infections. 

According to her, a second possible explanation is a role for previous COVID infection. And they know that this was very common in the children. Around 70% had evidence of past COVID infection. And it could be that in some of these children who were then exposed to adenovirus, they had a hyper reactive immune response that led to liver inflammation and hepatitis.

But it was also noted that only 10% of the affected children had current active COVID infection. So we don’t think that active COVID infection plays a part or is a cause. But there is reassuring news going forward in that the number of cases have declined and these cases remain rare, and the majority of children recover. But it’s important that countries remain alert to the possibility of further cases. And that they have in place referral pathways, and facilities to provide appropriate care. And for parents to remain aware that if their child were to develop symptoms of gastroenteritis, which were to worsen or to develop jaundice, they would seek medical care promptly.