Tegan Taylor: So Norman, back in 2022, we were doing Coronacast, the show all about the coronavirus, and one of the things we talked about at the time was a rare but really worrying trend of very young kids coming down with severe liver disease. It was a really similar syndrome happening in kids all over the world. And doctors didn't know what was causing it.
Norman Swan: Yeah, it caused a lot of fear. I think we were slightly less affected by it in Australia than other countries, but it did occur. And people were wondering what was causing it, and they thought that maybe it was a family of viruses called adenoviruses. But these kids were really quite unwell and some needed liver transplants.
Tegan Taylor: Yeah, and some even died. So a group of Australian researchers have just very recently pulled together all of the data that was from that time, 33 studies from all over the world, to see if they could solve the mystery. And I've been speaking to one of the authors, Guy Eslick from the Australian Paediatric Surveillance Unit.
Guy Eslick: So it was pretty scary that all this sort of stuff was happening, and particularly because it only affected kids under the age of 10.
Tegan Taylor: And it was severe.
Guy Eslick: It was severe. So at the end of the outbreak, 6% of these kids needed liver transplants and 2% of them died. And in total…
Tegan Taylor: And to put that into numbers, we're talking 214 kids who had liver transplants and 66 who died. That's pretty awful.
Guy Eslick: That's right. And this happens really quickly. So, if you have acute liver failure, you go from being a very well child to developing diarrhoea and vomiting, you quickly develop jaundice, you become very, very ill. And you could have a liver transplant within a week after developing those symptoms, if you're lucky. You can see how quickly these things happen. And I suppose particularly after Covid, we know what a pandemic is. And this was quickly spreading around the world. And we thought by doing the meta-analysis and systematic review that we would bring everything together and it would hopefully give us a better picture of what was happening, and in some ways it did, and other ways it didn't.
Tegan Taylor: So it's not that uncommon that kids get hepatitis, but this was out of the ordinary, it was a really specific type of hepatitis, it was happening in clusters, and it was happening in the same kind of way in different places all over the world.
Guy Eslick: We looked at all the countries that were involved, and we plotted their lockdowns, and then we plotted when the cases started. And if you look at it, the cases started to appear basically six to eight months after lockdown ceased in all of these countries. And these kids are young, the average age of these kids was three and a half. So they've been in lockdown for more than maybe 12 months in some cases, and some of them may have actually even been born in lockdown. So they've never been exposed to other pathogens in society, and so the hypothesis was basically, well, we came out of lockdown, these kids were let back into the real world, and then they got affected by viruses that then affected their liver because their immune system couldn't cope with it and that's what induced their severe acute hepatitis. And so that's one of the hypotheses that's going around about this potential outbreak.
Tegan Taylor: One of the specific types of virus that you identified as being a common denominator was adenovirus, or adeno-associated virus 2, forms of what we used to just call the common cold, we're narrowing down on them a bit. Is that the leading theory now, that that might have been the trigger?
Guy Eslick: Look, there's still a lot of work going on around this. I mean, certainly what we identified was that up to 83% of the children who were affected with the severe acute hepatitis had the adeno-associated virus 2 in their bloodstream. The perplexing part was that in the children that had had transplants or had died, they could not identify any viruses within their livers. Now, that's not what you'd normally expect, if you get an adenovirus that affects your liver and causes hepatitis, when you look at that liver tissue and you look at it under the microscope, you're going to see adenoviruses, or you could even try and identify them using other molecular methods. That was not the case here, they didn't see anything. So that is also a bit of a mystery, because while the children had the virus within their blood, they didn't have it within their liver tissues.
Tegan Taylor: So in some ways, despite this really careful combing through all the available data, it's still really a mystery, which is pretty unsettling when we're talking about such a severe disease in such young kids. And it's something that Guy Eslick says really speaks to the importance of gathering as much data as possible in any kind of outbreak.
Guy Eslick: The unfortunate component of this is that, as scientists and researchers, ideally what would have happened would have been that tissue samples and blood samples from all of these kids would have been kept, that could be used further down the track to work out; are there other causes, what's happened? That hasn't always been the case, and that is also an issue because when you've got kids coming in with acute liver failure and you're doing transplants and children are dying and you've got a large number of other sick kids in a unit, you're focused on obviously helping and fixing the kids, you're not really thinking, oh, there's a major outbreak of something here, I should be making sure that we keep liver tissue and blood samples and stuff like that. And the problem is that once those tissues and blood samples have been disposed of, you may never solve the mystery, and this may happen again. It's a bit like Covid, in a way; if you don't identify the source, you'll never be able to say it can't happen again.
Tegan Taylor: It's always a bit uneasy when you don't have a nice tidy answer, and I really hoped that you'd be able to give me one.
Guy Eslick: I do feel that. I mean, to be honest, when my student came to me and said, 'Look, this is what we've got,' I'm like, well, that's not really what I want. But it's not about what you want, it's about what you get, and then making the best out of that. I'm currently being asked to review a lot of papers from other researchers that are doing work overseas, so there's still people looking into this and trying to do stuff, and I think that's important, because what I hope doesn't happen is that these kids just get forgotten. And it's like, oh well, that happened, do you remember…we'll be talking about a bit like Covid; do you remember that outbreak that occurred years ago? I don't want that, you don't want this to happen again. The aim should always be to identify a cause and work out how to stop this from happening. So, look, I hope that there's a lot more research going on in the background that I'm not aware of, that comes out into the community. And I hope someone does say, look, we've identified a potential cause, but it is so difficult to do sometimes.
Tegan Taylor: Associate Professor Guy Eslick from the Australian Paediatric Surveillance Unit based at the University of Sydney. And Norman, not the satisfying neat bow that I was hoping for there.
Norman Swan: No, but good that he's reviewed the evidence, and it may illuminate some other problems of the future in terms of immune responses and so on.
