UMAIR IRFAN: This is Science Friday. I’m Umair Irfan. I’m a science reporter at Vox, and I’m sitting in today for Ira Flatow.

This spring, there’s been a strange spike in hepatitis cases among young children. Hepatitis is an inflammation of the liver and can leave kids with stomach pain, jaundice, and just that icky feeling. This sudden rise in cases is unusual, and physicians are trying to unlock the mystery of where this is coming from. Joining me to talk about this and other science news this week is Kathleen Davis, a producer for Science Friday. We’re glad to have you, Kathleen.

KATHLEEN DAVIS: I’m glad to be here.

UMAIR IRFAN: So Kathleen, tell us a little bit about this outbreak. When did this start?

KATHLEEN DAVIS: So over the weekend, the WHO published a report about a cluster of cases of acute hepatitis. The first cases were reported at the beginning of April. There have been 169 cases reported since then. That might not sound like a lot, but in a majority of these cases, the kids have been hospitalized. So these aren’t just normal hepatitis cases. These are on the serious side of the spectrum.

Friend of the show Katelyn Jetelina, who has a newsletter called “Your Local Epidemiologist” broke this down really well this week. She says there’s a big question that needs to be figured out. Is this a true increase in cases, or is it just that parents are more aware about hepatitis right now so they’re actually testing their kids for hepatitis at a greater rate, and kids are getting diagnosed more often? Another unanswered question is why these hepatitis cases are showing up in kids. It’s not that uncommon for kids to get hepatitis, but it’s rare that the cases are this severe.

UMAIR IRFAN: Are we seeing this outbreak scattered all over the world or concentrated in a few areas? Where is it happening?

KATHLEEN DAVIS: A majority of these cases have been in the United Kingdom. That’s 113 kids. There have been a handful of cases in other countries, including the United States. Of all of those US cases, nine in total, they’ve all been in Alabama. The ages of the kids in this report range from one month old to 16 years old.

UMAIR IRFAN: And you mentioned hospitalization. How serious can this hepatitis get?

KATHLEEN DAVIS: So acute hepatitis, which is what the WHO looked at, is more serious. As I said, pretty much all of the kids in this report were hospitalized. 17 of those kids required liver transplants. And there has been one death reported. So certainly, these are more serious cases.

UMAIR IRFAN: And you mentioned earlier we don’t quite know where the spike is coming from. But do we have any inklings as to what might be at work here?

KATHLEEN DAVIS: So as Dr. Jetelina wrote in her breakdown of this, there’s some disease detective work going on. One hypothesis is that this is related to adenovirus. Some of these hepatitis cases in the UK were co-tested for adenovirus, and 3/4 of those were positive for both. There are over 50 strains of adenovirus that infect people. In kids, these can cause diarrhea, tonsillitis, and ear infections.

It is important to note that the strain of adenovirus that has been identified in these kids that also had hepatitis is super common. So it’s very possible that these kids just happened to have adenovirus anyways. Correlation does not necessarily mean causation in this case. It’s very possible that these kids just happened to have this adenovirus and hepatitis at the same time, and they are not tied together.

A tie to COVID-19 infection is also a possibility, or another novel virus. There’s just a lot of detective work that still needs to happen here. If you’re worried about your kid getting sick with hepatitis, the WHO is recommending that kids and their parents do what hopefully they’ve been doing throughout this whole pandemic– following basic cleanliness and hygiene, things like washing your hands regularly, not standing in front of someone who’s coughing, things like that.

UMAIR IRFAN: Well, speaking of COVID-19, you have another story for us about vaccines for young kids. What’s going on there?

KATHLEEN DAVIS: Right. So the people that I know who are parents of kids under five have been waiting so patiently– in some cases, not so patiently– for their kids to be able to be vaccinated. As you know, vaccines have been available for adults for almost a year and a half now. Kids older than five have been eligible to be vaccinated for a few months now. But for kids younger than five, it has just been a waiting game.

The FDA has delayed action several times on approving vaccines from the big manufacturers that we’re very familiar with at this point, particularly Moderna and Pfizer. But it’s a complex situation. The FDA says it wants as much data as possible from these manufacturers to prove that these vaccines are going to be safe and effective for our youngest kids.

UMAIR IRFAN: Have there been any more recent developments? And do we have a better sense of the timeline?

KATHLEEN DAVIS: Yeah, so Moderna said yesterday that it had asked the FDA to authorize its COVID-19 vaccine for our youngest kids. This would make it the first manufacturer to do this. According to Sharon LaFraniere at the New York Times, an official at Moderna said it would finish submitting its data by May 9 to regulators. It is interesting that Moderna wants to jump all the way down to six months, since their current COVID vaccines are for 18 and up. So that would be a really big jump. Pfizer is the only manufacturer of vaccines that are available for under-18s at this point.

UMAIR IRFAN: So if these very young kids do get approval to get vaccinated, I mean, how big of an impact would it have at this stage of the pandemic?

KATHLEEN DAVIS: I mean, there are about 18 million kids who aren’t eligible to be vaccinated yet. So from a public health, public immunity standpoint, it would be great to have more people, no matter how little they are, immunized. But it’s also a peace of mind thing for a lot of parents. If you’re a parent and you’ve been living through this pandemic hoping your kid doesn’t get sick, this would make a lot of people more comfortable, right? You would feel safer sending your kids to school or sending them to the playground. Going back to normal life would seem like more of a possibility for a lot of parents.

We are, though, in an interesting place in the pandemic where it does feel like things have calmed down a little bit. The demand for vaccination just isn’t as strong as it was in 2020. People aren’t knocking down the door to get vaccinated right now. So some pediatricians think that because disease burden is less massive in the community right now, this might actually be a harder sell for some parents. So we’re just going to have to wait to see how this plays out.

UMAIR IRFAN: So switching gears, then, there’s been this massive heat wave going on in India and Pakistan. Just how bad has it been?

KATHLEEN DAVIS: It has just been brutal. So temperatures have reached 113 degrees Fahrenheit in some regions. And experts predict it could get as hot as 120 degrees in the coming days. The average temperature for last month reached the highest that it’s been in 122 years. These are countries where heat happens, but to give a little bit more historical context, India’s average temperature has risen more than a degree Fahrenheit since 1901.

UMAIR IRFAN: And what’s driving this? Like, what are some of the factors here?

KATHLEEN DAVIS: Well, to probably nobody’s surprise, there is a climate change component. A UN report found that India will be one of the most affected countries by climate change. For example, scientists project that heat waves in India will be longer and more intense as a result of climate change in the future.

UMAIR IRFAN: And of course, India and Pakistan are some of the most populated countries in the world. How many people here are at risk?

KATHLEEN DAVIS: Yeah, so CNN reported that this heat wave is affecting more than 1 billion people. That is billion, not million. And as you can imagine, it’s putting people in life-threatening situations, especially the elderly, those without AC or easy access to drinking water. I mean, all of these people are at increased risk.

UMAIR IRFAN: Well, staying on this note of grim news, unfortunately, there’s also been some bad news for reptiles. A whole bunch of them are at risk for extinction. Just how many reptiles are at risk?

KATHLEEN DAVIS: Yes. I wish I had some happier stories for you this week, Umair. But things are really bad for reptiles right now. Researchers looked at more than 10,000 species, and they found that one in five of them are headed towards extinction. That’s according to this new paper in Nature. That means those lizards, turtles, snakes that we all know and love are in a bad spot.

How do you feel about reptiles, Umair? I know there are– some people like them. Some people don’t really like them. But what about you? Are you a herp enthusiast?

UMAIR IRFAN: I like to keep a respectful distance.

KATHLEEN DAVIS: OK, that’s very fair.

UMAIR IRFAN: But losing any species is bad. But do reptiles play a particular role in the ecosystem that we should be concerned about?

KATHLEEN DAVIS: Yeah, reptiles hold an important place in our ecosystems. They eat insects and rodents, which we people commonly see as pests. They hold this intermediate role in the food chain. They are in between insects and the big predators of reptiles.

UMAIR IRFAN: And I’m guessing this extinction is somehow our fault, or partly?

KATHLEEN DAVIS: Yeah. That’s a very appropriate guess. The biggest causes are habitat destruction from farming, urban development, and logging, so the usual suspects. And though this research is upsetting, it’s important for scientists to know where reptiles are most at risk so that we can go about protecting them.

UMAIR IRFAN: Let’s end today on this story you brought us about mushrooms. You know, I like mushrooms. They taste great. But I don’t think about mushrooms as being male or female, and it turns out that not only do mushrooms have a sex, they actually have lots of them. Tell me about that.

KATHLEEN DAVIS: Yes. So mushrooms are just so cool. They’re also very tasty. And this is another example of why they are so interesting. So researchers reported in the journal PLOS Genetics that some species of fungi have thousands or even tens of thousands of biological sexes. This is really hard for me to wrap my head around. I am sure I’m not the only one.

The way that these researchers found this out was with some really cutting-edge genetic tools. They used these tools on a group of mushrooms called Trichaptum. These are pretty common mushrooms. You’ve probably seen them if you like to go on hikes or walks in the woods. They look like plates or flat shells. And they love to decompose dead wood, so you often find them on trees.

So from 180 specimens of Trichaptum mushrooms, they sequenced their genomes. And they found that there could be 17,550 different sexes possible for these mushrooms.

UMAIR IRFAN: So what can we read into that, or what are the implications of that?

KATHLEEN DAVIS: I mean, it just shows that reproduction is really complex for mushrooms. It’s not like people. They have their own thing going on. Having so many different possible variants of sexes means that it’s more likely that if you are a mushroom, a neighboring mushroom will be reproductively compatible. There are still a lot of unanswered questions about this, but this might be a clue into why some fungi are just so resilient.

UMAIR IRFAN: Mushroom Tinder must be wild.

KATHLEEN DAVIS: Yes, I’m sure it is just a wild place.

UMAIR IRFAN: That’s all the time we have right now. I’d like to thank my guest Kathleen Davis, producer for Science Friday. Thanks for being here.

KATHLEEN DAVIS: Thanks for having me.

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