Listener supported WNYC Studios. Wait, you're OK? You're listening to Radiolab Radio from WNYC. Hey, I'm Jad Abumrad. This is Radiolab, and today, a story from our very own Molly Webster.

So, yes, today we're talking about a medical mystery. Oh, good. Let me put my on my wall. Kept them. Because he really is he really is putting on a walkout. OK. OK. A medical mystery. Yeah. Starts with a woman, hello. Hi, I'm trying to reach D'Rivera, a player named Joe Veria Farooqi. This is of a how are you? She works at a hospital at a teaching hospital in Pakistan, in Karachi, the Alkon University.

And I'm a medical doctor specialized in medical microbiology.

Gervasio works in the hospital lab.

And so when someone has an infection, she gets sent, you know, some blood or urine or something, and she tries to figure out which bug is causing the problem.

So the very first bug that I was in the lab in the fall of 2014, the third week of October, I found three bugs in the blood of three different patients, which looked exactly the same and like nothing she'd ever seen before, creamy in texture.

It had a whitish dream and had another ring of light brown around it, white center and very, very white. It's sort of like when you put UV light on on white and it sort of shines with a bluish stand.

And what you saw wasn't a bacteria or a virus, it was actually a fungus, I guess. But beyond that, she sort of had no idea what it was.

I shared it with all my friends who were working in other labs, and I asked them if they had encountered something like this and they all said no, but the patients were all very, very sick.

Yeah, well, so what happened is that we started seeing patients with fever, high Whitesell gowns of the three patients those samples had come from.

We're all the same hospital under the care of this guy.

Dr. Fesperman, move them. An infectious disease specialist here at the Alfred University.

And all three of them were patients in the ICU, older patients, folks who have been in the hospital for a week or two weeks.

You know, with patients like that, they definitely deal with fungal infections from time to time. So the symptoms were really nothing, nothing spectacular, nothing weird.

But when he found out that they all came down with the same mysterious fungus all at the same time when it was identified, we like, OK, that's that's we are maybe some kind of coincidence.

But then while I was looking at those, I encountered yet another one. Another one popped up exactly the same yeast and another one popped up in the same hospital, but this time not from the ICU.

And I thought, oh my God, which was really strange because they have never seen this fungus before and suddenly it's popping up all over the hospital.

I would have been okay if it was just one case or two cases in a whole year. That's all right. However, to encounter them in a hole in a cluster is alarming. You know what to doing in a hospital behaving so angrily and killing people off. I mean, two of our patients had died by then.

You know, we just sort of kept seeing the doctor. I think within six months we had like nineteen cases and by then six months in, eight of the patients had died.

So this fungus is pretty nasty. Yeah. I mean, the people who get it seemed to have an other sicknesses as well. But but once you got it, the mortality rates like 20 to 60 percent. Oh, damn.

And that's about the same time. When Jivaro sent some strains to the US CDC, Gaviria basically sent them an email and just said, you know, hey, will you look at this thing?

And this is when the mystery of this fungus went way, way beyond one hospital in Pakistan.

We were informed by colleagues in Pakistan that they were having a large outbreak in.

One of the guys that got that email eventually was Tom Chiller, chief of the MicroTech Diseases Branch here at the Centers for Disease Control and Prevention in Atlanta, Georgia.

And he and his colleagues pretty quickly identified the fungus as Candida Auris, the city's scandal.

Iris and I'm like of what they were going to ask.

Now, Canada is kind of a big group of fungus. It lives on our skin and in our guts and can cause yeast infections and thrush and babies. But this particular Canada was totally new.

It was first isolated from an ear infection of a Japanese patient, and that was in 2009.

And it was really just causing some sort of goopy goop to leak out of this woman's ear on the skin where we know some candida species can be.

And we didn't think honestly much of it until six years later.

They hear from Joe Veria that this Canada Auris is getting into people's blood and causing serious infections, you know, horrible bloodstream infections and even death.

And so we thought, OK, this thing that we saw once that we did not think was a big deal is now killing people.

So what's going on?

And so he started poking around and he came across reports of Canada, Auris outbreaks in South Korea, in India and South Africa had described.

Clusters, and we figured we found that it's it's popping up all over the world and actually while looking into this, colleagues from London where we're we're we're talking to us about a very similar phenomenon with the same organism.

The hospital in London had an outbreak to the point where they had to close their intensive care unit for a period of months.

So what we saw were that that there were essentially four different clades, for lack of a better word, that were emerging in three different continents, all about at the same time, meaning it wasn't like it started in one place and then went to all these other places.

It couldn't be explained by travel. It couldn't be explained by, you know, by the fact that these were in some way related, except that they were the same species of organism. They truly were emerging at around the same time in four parts of the world.

So the big question that arises out of this moment is why now?

Yeah. We just so make sure I'm getting this, you have one fungus appearing in four totally different parts of the world simultaneously, simultaneously weird. It's definitely not normal. No, it's absolutely abnormal and, you know, people around the world are trying to figure out how this happened, why it happened, why is it and so this is Snigdha Valbuena and she was part of the team at the CDC that was tracking the fungus and trying to figure out what was going on.

So initially we thought, like, could is it possible as some contaminated medical product or something that got distributed, something that got distributed to these hospitals, but then they thought four different hospitals on three different continents? I mean, you don't expect it to be that worldwide. So it's like scratch that. Maybe it's the way, you know, different antifungal drugs have been used around the world, like we all use, you know, antifungals in our body.

But the more important thing is, is farms using antifungals where they spray their crops. So it's maybe the fungus or damaging to fungicides and it's just getting stronger.

So it would it be that the farmers are training the fungus and those fungus are then somehow getting away from the farm and into the hospitals or.

Yeah, OK. But that still doesn't explain why it would happen. And all these separate places and this one particular moment, why now? Right. You need something that was happening to all of these fungus in different places at the same time.

That's why people are looking for more of this not just environment, but sort of a bigger picture, ecological analysis.

Meaning what?

Well, I just at this point feel like I should just start talking about dinosaurs.

It it it is a little bit of a detour, but I promise it will pay off, you know, survivalist dinosaurs in general. I'm like, oh, God, here we go. There is a lot of history there. Ladies and gentlemen, please welcome to the stage, your host for this evening, Jad Abumrad and Robert Krulwich. But trust me, it'll be worth it. That's the. To loop everybody in about seven years ago, we did a live show called Apocalyptical that had life sized dinosaur puppets, traveled 21 cities, super fun, but it completely broke us and we all nearly died.

Yes, it's true. But part of that live show is a story that I reported for you guys about an asteroid that hit the earth and put an end to the dinosaurs.

So it turns out on that day, as the fire was raging above on the surface, somewhere in a little hole in the ground happened to be a furry little animal.

And about how after the cataclysm is mammals, small little mammal crawled out of its little muddy burrow into a dinosaur world and became the great, great, great, great, great, great, great, great, great, great, great, great, great, great, great, great.

Great, great, great, great. Cetera, grandma of everybody in this room, it is true there was a creature down there. There is a creature down there. I thought we should stop there because we were getting away with something and I didn't want to push it too far. All of a sudden, it was just, you know, oh, Miss Robert. I know.

Well, anyhow, continue story goes like this with dinosaurs out of the way, the idea is that mammals crawled out of the hole and they just inherited the earth. So big reptiles out, crafty little mammals in. Yep.

But there is a new idea about this fungal friend of ours, this one we've been talking about, that sort of messes this story up a little bit.

So here we are in the realm of hypothesis, speculation. We don't really know what happens 65 million years ago or 100 million years ago.

The idea comes from this doctor and microbiologist, Arturo Casadevall at Johns Hopkins University. And he says the first few bits of our story are all good. Right?

We know that there was a catastrophe. The asteroid hit the Yucatan and we know that the Earth had a really bad day. And the animals that then follow are is the age of mammals.

Yeah, because I feel like we, like, took down all those dinosaurs and there's a big hole and we're like, oh, and we crawled out of.

I think that people thought that, you know, because the dinosaurs were wiped out, that he created a space.

This is absolutely what I think. Right. So there is a little bit of a problem with what in my mind was and and I and I and I add that this is my problem. But I'll show you what the thinking is.

If you look at our world today, we still have reptiles, a crocodile infested river bank. We have alligators. This is our Dabu and VIPR from West Africa, have lizards.

Monitor Lizard is out hunting, looking for the entrance to the galleries in which the mammals take shelter during the daylight hours.

So clearly, some reptiles survived the catastrophe.

There were reptilian creatures that were living in that, you know, riverbank in the same way that the mammals were and got out of the fires in the ash and came out.

And it's always bothered me. How come we didn't have a second reptilian age?

So you actually have a moment when either of them could have taken the crown?

I thought the idea is it just we got we got lucky. I mean, we would have had to be really lucky because according to our turo, reptiles had two big advantages over us.

Straight out the gates, first one being reptiles, in contrast to mammals, don't need that much food, which, you know, is great, because at the time most of the plants had burned up, the planet was covered in ash.

There really wasn't that much food. And whereas mammals have to eat all the time, like reptiles can just chill for a while. So that's definitely a win for reptiles over mammals.

They also reproduce a lot faster.

The second one is that they just make more babies. If they can spread a lot faster, their chances of survival are greater.

So Arturo's like if the reptiles are able to do well with less food and they reproduce faster, why didn't they just take off and create a whole new world which is reptilian to now his idea for why this didn't happen, why there wasn't a second reptilian age, is that there is another player on the dyno free stage, a small, invisible, yet powerful player.

And to understand, you have to know that before the asteroid hit, it was it was a forested planet that there was, in fact, a lot warmer than it is today. There were forests in many parts of the world. The cataclysm is thought to have led to rapid temperatures that fell. And you also had no sun. So imagine a dark, cold world of decaying vegetation. This cataclysm was associated with a massive proliferation of fungi. Hmm. And actually, if you look at like the right above the KT boundary, that line that demarks, you know, no meteor, meteor, dinosaur, no dinosaur.

Yeah. If you look right above there, it's the soil is filled with spores. No. And so everyone knows it's really well documented that as a layer after the impact, yes, there is a layer one or two up which is filled with fungi spores.

Yes. And so we said it's very well known that there was fungus growing on things that got burnt, fungus probably just growing because it's wet and damp. And why not cause mold and mushrooms everywhere? Also dead bodies.

There's like things decomposing fungus like they love. I've heard parties.

Um, so it's like you have you have a couple of shrew like creatures walking around. You've got. You've got. Some alligators, but you've got a crap load of fish, you've got a crap load of fungus, fun, fun, fun, fun guy, fungi, fungi or fungi, whatever, you know, Ravelli, whatever you take seriously. Some people pronounce the fungi. Some people pronounce fungi, OK, or fun anyways, whatever you call it, if you are an animal or reptile or a mammal, fungi can be deadly.

That's right. And while reptiles could skip meals and make a bunch of babies, when it came to fending off fungi, we had an advantage. We have two pillars to protect us.

One of them is that we have advanced immunity. The immune system is obviously like the kung fu fighter. It really takes up like the weight of keeping something out.

But the other thing that we have, the frogs don't have and the trees don't have and that insects don't have is that we're really hot relative to the environment. We're warm, we're warm blooded.

Mammals actually use some of their energy to keep their bodies warm. So if you think about us, it could be really cold outside. It could be really hot outside. But we stay at a steady basically ninety eight point six. Now, if you're fungi, you actually like it kind of cold.

They do very well until about 30 degrees, like 86 degrees Fahrenheit. Right.

Any hotter than that, denature them irreversibly. The proteins start to fall apart. The cells start to melt. And so if a postapocalyptic fungi got into a postapocalyptic, very warm mammal, it would die.

These high temperature creates, you know, a heat barrier. And this heat barrier means that the majority of fungal species out there cannot grow or replicate inside your body because you're too warm.

Our heat keeps the fungus out. You got it. If you are a reptile, you're cold blooded. You don't have a way to keep yourself, like, steady and warm. You have to go look for ways to become warm, you know. Have you ever seen the lizards lie on rocks, you know, where they're just like out in the sun, soaking up the heat or so that will warm their bodies up? But also and I never knew this, it also will clear like fungus from their body.

Oh, so if they're sick because it warms them up so much that warmth attacks the fungus, do they not, to fevers? They don't they can't do fevers. So their way of getting as hot as possible is doing that sunshade thing.

I know.

So he was saying that if you're a reptile and you get a fungus, but there's no sun to warm yourself in because because the apocalypse has just happened.

It kicked up the dust, blocked out the sun, nuclear winter. So you die because you can't withhold the fungus. But if you're a mammal, a fungus comes, your body temperature naturally kills it.

And so suddenly his theory goes interest of mammals filling the hole and really flourishing in a way they never did before because fungus helped them do the mammalian explosion.

Right. Because where we went through this fungal filter and therefore we are no longer a fungal filter at the end of the Cretaceous. Wow.

Now it gets even weirder because then Arturo decided he wanted to find out if you are warm blooded, what was the optimal temperature by which you get the most protection against the fungi, and yet you don't have to eat all the time.

And what is the optimal temperature to keep us from eating all the time, but still give us defence? The reason we eat three meals a day is to stay warm and functioning. We were less warm. We could eat less.

So it's like how little can we eat and still be protected against fungus and yes, stuff.

That's correct.

And what we've did and so what Arturo did was he got together with this mathematical biologist of Burkeman and first they just gathered some numbers.

What is the temperature susceptibility of fungi like?

Most fungi don't like it above. Eighty six degrees Fahrenheit. And then he looked at the well known formulas for calorie use. And then he asked the question, if you put these two formulas together, what is the best temperature that keeps out most fungi but doesn't require you to have to eat all the time?

They basically crunched a number that had to do with like how many calories you need a day. And like like just like the energy that would take of eating and then keeping out pathogens.

And what he found was that our temperature ninety eight point six is that temperature that best balances protection against fungi. Very. Assess the need to to to eat food, whoa, bing, bing, bing, we we were amazed and tickled by it.

And he's saying the reason our bodies are precisely ninety eight point six degrees is because a fungus like they shaped us to be that.

My heart wants to say yes. But to caveat, he did say it could be totally correlational. Right. Obviously, he's not been able to take the temperature of any of our ancient ancestors. But, you know, it is a very interesting.

Idea that part of being a mammal is about being good at fending off fungi, unless part of that equation changes, which you will after the break.

This is Miranda Ballard calling from Nampa, Idaho. Radiolab is supported in part by the Alfred P. Fund Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at W w w dot Sloan Drug Science reporting on Radiolab is supported in part by Science.

Sandbox is Science Foundation initiative dedicated to engaging everyone with the process of science.

This is Radiolab, I'm Jad Abumrad. I'm Molly Webster. OK, where we left off, you told us the startling fact that our bodies may have chosen ninety eight point six degrees to fend off fungus. But then you said somewhat ominously, that is unless the equation changes, which it will. Yeah.

So this brings us some might say, finally back to our medical mystery, which is that our wonders what if in light of this dinosaur mammal fungus detente, this thing that seems new, Candida Orris has actually been here the whole time.

So say these fungi typically live outdoors in soil and on rocks, and they live in a place that's like, you know, normally 75 degrees. It's a way you want. Okay, let's say Hawaii, because they're into mushrooms.

They're their ideal temperature is seventy seven degrees. And if they go above that, they start to feel a little queasy, really start to fade. And it's a struggle. All right.

OK, so one day it's 81 degrees. And like the fungus like this is hot.

All foreign giants have the capacity to tolerate short bursts of heat. But you.

But what if the 81 degrees lasts for many days, not just one heat challenge. In that case, most of the fungus would die.

But the more 81 degree days there are, the greater the chances that in the Russian roulette of evolution, one day you would get a fungus.

So you know what? I think I feel pretty OK. And the reason that fungus probably feels that way is because it has like a mutation of some sort that give it the capacity to survive the heat. Maybe it can even fight a little harder.

Turning on some of the defense mechanisms like heat, shock proteins, however it does it, this one fungus lives and then it creates a copy of itself. And then that fungus has fungus babies, what you called a bug, and then that blood has buds.

So the original cell may make 50 copies of itself before you basically run out of fumes to make any more blood. And so suddenly you have a whole batch of fungus that survive at 81 degrees. Yeah, OK. And then after that, you take the survivors and you expose them to ninety degrees, let them sweat it out and then boom, you got a whole batch at 90 degrees. You got it. And you can just keep pumping this up degree by degree.

Exactly. A string of ninety one degree days and ninety two degree days. Ninety three degree days. Ninety four degree days. Ninety five degrees. Ninety six degrees. Ninety seven degrees. Ninety eight degrees. And ultimately ninety eight point six degrees.

Now you have the capacity to survive inside the body of a human.

It reminds me of water, like if you're water and you go from 34 to 33, you're still water. Thirty three to thirty two, you're still water. But there's the seemingly insignificant threshold between thirty two to thirty one that when you cross it, you become ice.

And it is this almost my new transition that our two things happened with Candida Auris, that it was out there living in the environment and it gradually adapted to be able to grow a higher temperature and it and when it did that, it acquired the capacity then to cause issues in people. Essentially it is adaptation. They feed it are heat defences. Wow. Yeah. Yeah.

So fungus are being trained by the rising temperatures and they're adapting along with those rising temperatures.

You got it. And then and then suddenly it's not that far from like, you know, that fungus in a soil getting caught on somebody's shoe who walks it into a town that then goes into a hospital, into an IV line.

It can get into a wound and then it can colonise patients.

Huh. That would explain why Candida happened in all those places simultaneously. It was always in those places being tracked in on Boutte's into hospitals, but only now it gets tracked in with this new ability to live in us. Yes. Wow.

Japan is suffering its hottest day on record. And this is an interesting thing.

Like like all of a sudden it made me think about all the headlines you see around the world and in India, it's rarely been this hot about like the country has been experiencing a deadly heat wave with dry air far hotter than the human body. It's the it's the tenth straight day above one hundred and five degrees.

And in Delhi, all across the west, you know, or it's like it was another day of oppressive heat. Idaho's having the hottest August on record. Funerals were underway way in Karachi on Friday for some of the victims of the scorching heat wave.

You know, many people say when you tell them about this, but how can that be? You know, they say that the average warmth, it may be one degree centigrade.

This is a so-called cooling station in Las Vegas. I say that's not the right way to think about it. The right way to think about it is to imagine triple digit temperatures, the number of really hot days, because each hot day is a hoop you've got to jump through.

And then just one last dash of interesting in looking at all this like fungus temperature stuff, just as the fungus are learning to jump through our hoops, it turns out we are actually making it easier for them.

What do you mean?

So there was actually in looking at all this like fungus temperature stuff, there is this paper recently that was talking about how the human body temperature has been declining. It's been steadily declining for decades at a rate of like point, oh, five degrees Fahrenheit per decade. Really?

Yeah. So we're not ninety eight point sixty more. What are we?

They think it's actually more around like 97 five. But in fact you're what they're. Do you get that a lot when you measure your kids.

Yeah. I'm always like, oh you're, you're not, you're not. You're colder.

The one thing that the researchers were talking about, though in the declining is that they looked at Western records.

But, you know, they say, well, they did a small study on people in Pakistan and they were more around ninety eight point six.

And the researchers were talking about how essentially how hard your body has to work to stay healthy. And consequently, the health care system that you're in is what is like affecting the temperature decline. So I don't think they think it's like world wide. I think it's a it's like a developed country, western kind of thing.

I see. So in countries where there's more advanced health care, you're going to see internal body temps start to lower, basically.

Yeah, well, so essentially in some of the areas, you know, this head to head between fungus and us and it is a very fine line going from being insignificant to, you know, king or queen of the castle.

Many organisms that you recover from the environment can only grow at environmental temperatures, but some of them have a whole range of temperature susceptibilities or temperature.

Resistance was a better way to put it, and some of them happened to their Maximon happens to be just below your temperatures. And these are the ones that we worry about because many of them may have the capacity to cause disease, but they. Cannot do it because they cannot survive. What are the other ones that are just below my ninety eight point six? Well, there are probably yeah, I don't want to be alarmist, but there are probably in the in the in the hundreds of thousands or even millions.

I mean, I don't want to be alarmist either, but now I want to know what's like what's like marching at my heels. Yeah. Right. Wow. That's just so weird. Like out of all the things that climate change can do to me, I was not thinking about like it's warming up microbes on the sidewalk and they're like, oh, finally I can crawl into this is the moment we've been waiting for over millions of years.

It's so much easier. Yeah. Wow. Molly, thank you, I guess, for just giving me one more thing to have nightmares about. Sure. I am always happy to see your fears.

This story was, of course, reported by Molly Webster, produced by Molly with Bethel Hobday. Production help from Tom Davis. Special thanks to Lewis Ostrosky until next time. I'm Jad Abumrad. Thanks for listening. Hi, this is Katie from Boulder, Colorado. Radiolab, created by Jad Abumrad with Robert Krulwich and produced by Storm Wheeler. Gilinsky is our director. Why you left? Hamburg is our executive producer. Our staff include Simon Adler, Jeremy Bloom, Erica Bressler, Rachel Kucik.

David that perhaps Tracy I'm not guilty. So low. Annie McEuen, Lackies Maslach, Derek Carr, Arianne Black Hat Walters' and Molly Webster with help from FEMA only Alice Harrison and Russell Gragg. Our fact checker is Michelle.