IRA FLATOW: This is Science Friday. I’m Ira Flatow.

I don’t know about you, but it’s been a long time since a zombie apocalypse show has kept my interest for more than, let’s say, an episode or two. But The Last of Us, from HBO, has me hooked. It’s based on a video game in which a fungus, a fungus spreads throughout the food supply and infects most of the world’s population, turning ordinary people into murderous mind-controlled monsters.

[AUDIO PLAYBACK]

– Billions of puppets, with poisoned minds, permanently fixed on one unifying goal– to spread the infection to every last human alive by any means necessary.

[END PLAYBACK]

IRA FLATOW: And to no surprise, one of my favorite plot lines is about the fungus itself, where it came from, what it does, how it spreads. So today we’re going to separate fungus fact from fiction because many times fact is more fun than fiction. And I promise, no spoilers here.

Joining me now is Dr. Patty Kaishian, a mycologist and visiting professor of biology at Bard College in New York’s Hudson Valley. Welcome to Science Friday.

PATTY KAISHIAN: Hi. Thanks for having me. Happy to be here.

IRA FLATOW: Nice to have you. All right, what did you think of seeing a fungus in a show like this?

PATTY KAISHIAN: It’s been really exciting to see fungi in popular media because it’s really rare for that to happen actually.

IRA FLATOW: So in the show, we have a fungus called Cordyceps, correct? It takes over, turns people into zombies. Cordyceps is a real fungus, right?

PATTY KAISHIAN: Yes. So Cordyceps is a real group of fungi. The name Cordyceps is actually a genus of fungi. So you have a lot of different species within that group. But scientists, and mycologists specifically, talk about Cordyceps as a catchall for a lot of different groups of fungi that infect insects and kill their host.

The portrayal in the show is that the fungus enters the person’s body and grows throughout their skin and flesh and then takes over their minds. And this is something that happens with some species of these fungi on insects.

IRA FLATOW: Well, should we, people, be afraid, be very afraid, it could happen to us?

PATTY KAISHIAN: So I would say no. I personally do not live in fear of this happening to me, even though I study fungi and think about them all the time. And that’s because these relationships that exist now in nature with the fungi growing on particular insects are ones that have been developing for millions and millions of years. So they’re very host-specific, very particular to the chemistry and the physiology of the host body. And they’re not something that just can spread easily to other groups.

For a fungus to evolve that could infect humans in a similar way, it would take a really, really, really long amount of time, far beyond any of our lives or probably the lifespan of humans on this planet.

IRA FLATOW: Well, of course, that’s not to say that we don’t interact with fungus. There’s certainly fungus that can mess with our minds, right? I’m thinking of Psilocybin and rye ergot, which can cause hallucinations.

PATTY KAISHIAN: Sure, certainly. Yes, we’re interacting with fungi all the time in various ways. And of course, there’s a reputation that fungi are inherently dangerous and a risk to our health. And there are some species that can hurt us if we were to eat them– like you mentioned, the ergot, which is a rot that grows on different grains, especially rye. And if you eat that, it actually causes– sort of like a compound in there that’s similar to LSD, but one that’s really, really bad– and it can cause really disturbing hallucinations, but also physiological problems, like gangrene and things like that.

So we certainly need to be aware of the fungi that are around us. But there’s also lots of fungi around us all the time that are doing really helpful things in our environment. So most fungi are actually pretty beneficial for us.

IRA FLATOW: Give me an example.

PATTY KAISHIAN: Basically, most terrestrial plants have some sort of partnership with fungi. Meaning the fungus is providing nutrients, like nitrogen and phosphorus and water and other beneficial things to plants. And actually, 95% of plants on land have a partnership with a fungus in which they’re really depending on that fungus to survive.

So when you think about the forests that are around us and our agricultural systems, fungi are really intimate parts of those systems. And actually, we wouldn’t be able to recognize these systems if it weren’t for the important roles that fungi are playing in those environments.

IRA FLATOW: Right. So they do really useful things. But sometimes they can interact with us negatively. I’m thinking of people getting fungal infections, like athlete’s foot, stuff like that.

PATTY KAISHIAN: Yes, there are things that you don’t want. So athlete’s foot would be maybe a less severe type of fungal infection. And then, particularly people who are immunocompromised are extra vulnerable to various types of fungal infections that can become systemic. There are some species of yeast, called Candida, that can become dangerous to human health, particularly if your immune system is suppressed.

So certainly, we do want to know what’s going on with fungi. It’s really important that people are studying them and thinking about them in the context of human health. Because it’s true that some can pose a great risk to us.

IRA FLATOW: Yeah. But getting back to the show, there’s no fear of mind control, right? But the fungi can cause outbreaks like they did in the show?

PATTY KAISHIAN: Yeah. So I’m not afraid of like a zombie apocalypse caused by a fungus. But it is true that there could be outbreaks of other types of fungi that could be detrimental to our health. So Candida Auris is one species of fungus that is causing a bit of a stir. It used to be found mostly in desert climates in the US. But as the planet has warmed a bit, it’s starting to spread more and more north. And that can get into your lungs and cause some serious health problems for you. But nothing that’s going to fully take over your body and cause you to become a monster.

IRA FLATOW: Yeah. And there’s this really harrowing moment in the show when the mycologist says there’s no treatment, no hope for infected people. In real life, fungal infections, are they that hard to treat?

PATTY KAISHIAN: Yeah. So fungi are really hard to treat when they infect a human because fungi are actually more closely related to animals than they are to plants. So when you’re trying to kill fungal cells in your body, the medications that we have often are also harmful to our own cells. There’s often a large amount of side effects with fungal medications, and they can just be very persistent and difficult to fully eradicate.

The other problem, though, is that we know very little about fungi in general. It’s a really understudied discipline. So we just need more research to understand the life cycle of these organisms, their basic chemistry and biology, and even just to know what species are out there. So we just have a lot of work to do. So one thing that’s concerning about a potential fungal outbreak is that we would have very little starting information if it were to occur.

IRA FLATOW: And as a mycologist– I hope you don’t mind me referring to you as a fungi nerd–

PATTY KAISHIAN: That’s accurate.

[LAUGHTER]

IRA FLATOW: Well, then, you must be watching the show with a critical eye. And I’m asking that because I want to know if there’s anything else that the show gets wrong that really bugs you. Maybe “bug” is the wrong term here, but yes.

PATTY KAISHIAN: So I’ll start by saying that I really like the show and I’ve been really enjoying it. The storyline is well executed. I actually played the game when it came out, and I really enjoyed it at that time. And I think the show has been really gripping. And I love the costume design.

But of course, as a mycologist, I can’t fully take off my mycology lens. And I think one thing that kind of bugs me is during the credits, in the opening credits, they show a fungal-like organism spreading and traveling, and it ends up mapping out roughly the United States and continues moving. And actually, that’s not a fungus. What they’re showing is a slime mold, which is something that used to be in kingdom fungi, but it’s now recognized as being an amoeba. So that was a little bit irritating to me.

But otherwise, I think that the show is doing an interesting job in weaving elements of fungal biology accurately. But it’s also relying on different elements of fungi that don’t exist in one single species. So visually, a lot of the aesthetics of the fungi that are showing are other species, more like polypores, which are fungi that grow on wood and trees. And then they’re combining that with elements of the Cordyceps group. And then they’re blending in the slime mold. So there’s this panoply of fungal representation.

IRA FLATOW: Yeah, a lot of literary license going on here, isn’t it?

PATTY KAISHIAN: Yes, for sure.

IRA FLATOW: But one thing you did point out about that beginning of the show, where you see it sort of spreading, that’s really how– don’t fungi talk to each other through the ground? Because in the show, the infected humans communicate with each other through an underground fungal network.

PATTY KAISHIAN: Yes. So they’re relying on this idea of a mycelial web. So mycelia, or mycelium, is the network of fungal cells that extends through substrates. So through soil or wood or through animal tissue. And basically, we know that fungi can communicate over long distances through their mycelial networks. They can send information about their habitat. They can send resources to one another and to other organisms. So they are utilizing that reality to move the plot.

IRA FLATOW: Let’s take a listen.

[AUDIO PLAYBACK]

– They’re connected.

– More than you know. The fungus also grows underground, long fibers like wires, some of them stretching over a mile. If you step on a patch of Cordyceps in one place, and you can wake a dozen infected from somewhere else. Now they know where you are. Now they come.

[END PLAYBACK]

IRA FLATOW: Hmm. And the show talks about climate change, and that it could affect how fungi spread and behave. And that if the average temperature of the Earth goes up, that makes it more amenable to the growth of the fungi. Is that an actual concern?

PATTY KAISHIAN: So, yes. Climate change in all its forms is a concern for diversity. When we’re talking about a warming planet, there are some species that are going to go extinct when the temperature rises. Because all species have evolved to be successful in particular niches. And that’s often involving a pretty narrow temperature window. So if you go higher than that temperature window, a species can go extinct. And this is true for organisms, including fungi, but most organisms in general.

But that also then opens up windows for new species to thrive. So when you increase temperature, some will go extinct. And some can expand into that range and then be more successful. So we know that climate change is going to just really shift a lot of things. And overall, we expect there to be lots of biodiversity loss. And that’s mostly caused through habitat destruction.

But we know that changing rainfall patterns, certain areas becoming wetter, certain areas becoming drier, this is definitely going to lead to some species going extinct and other species thriving. So it’s hard to predict what that’s all going to look like. None of it’s particularly good, though.

IRA FLATOW: How did you like the way visually the fungi were drawn? There were actually very pretty, very gorgeous depictions of them.

PATTY KAISHIAN: Yes, I love the artistic rendering of fungi in this show. I think it’s done beautifully. Certainly, creepy. But as a mycologist, I’m used to dealing in what other people would consider creepy. So I think it’s done really beautifully.

Aside from it combining multiple aspects of different species into one, I think it definitely gives a very fungal feeling.

IRA FLATOW: This is Science Friday, from WNYC Studios. In case you’re joining us, we’re talking with mycologist Dr. Patty Kaishian about the fungi-inspired TV show, The Last of Us.

And how do you feel that fungus has become a topic of conversation now everybody’s seeing the show and talking about it?

PATTY KAISHIAN: It’s interesting. Mycologists are used to people ignoring fungi for the most part. In the last couple of years, there’s been a bit of a shift. Which is exciting. People are a little more open minded about learning about fungi and welcoming them into our lives.

So this is a more negative portrayal of fungi. But what’s really exciting is that it’s gotten a lot of people asking about fungi. So maybe if this show came out 10 years ago, I don’t know that I would be contacted for an interview about them. So this time around, I think because people were exposed to some positive press about fungi over the last few years, now people want to, as you said, sort fact from fiction. So I think it’s good overall.

IRA FLATOW: But you’ve been excited about fungi for years. I mean, what makes you so excited? Why do you love to study them?

PATTY KAISHIAN: So yes, I’ve been studying fungi for a little over a decade now. And I was really drawn to them because so few people understood them. They were this mysterious entity in the forests that really excited me. And I felt a natural alignment with them because of ways in which I guess, particularly as a younger, person moved through the world in a way that wasn’t necessarily particularly well understood.

So I just felt a kinship with them. I felt really excited by how dynamic they are in our ecosystems and how much potential information they hold that we know very little about.

IRA FLATOW: Tell me about that. So we less about fungi than we know about fungi, right? What else is there to learn?

PATTY KAISHIAN: There’s so much to learn. So I can start by saying we think that there’s over 3 million species of fungi that exist on Earth. And of that 3 million or so– possibly more– we’ve only described about 150,000 species. So really just a small sliver of the fungal diversity on this Earth has been described in a formal way. So we’re talking about millions of species that exist around us, some of them large, obvious, mushrooms, some of them micro fungi.

And we don’t know what they’re doing or how they’re doing it– so in terms of what ecological functions they’re playing in a forest or in a grassland or within a single leaf on a tree. We know that they’re involved in nutrient cycling and mutualisms between plants. They’re in our own bodies.

One really fun fact I have is that there are actually more fungal and bacterial cells in our own bodies than there are human cells. Which is a little bit crazy, but true.

IRA FLATOW: Our microbiome, we love to talk about it.

PATTY KAISHIAN: Yes.

IRA FLATOW: Why is it that we know so little?

PATTY KAISHIAN: That’s a complicated question. But I think that people have been disinterested in studying fungi because they didn’t seem important to us, particularly from the cultural framework of European-American Western science. And I think they were seen as things that were gross or creepy or slimy and deadly, and there was just a negative perception of them. And I think that that actually has materially impacted the formal study of them.

So it’s actually hard to find a place to learn about mycology in a formal way. There’s very few mycologists working at colleges and universities. Only a handful of institutions will grant degrees that are super focused on mycology. So we just have a long way to go in recognizing how important they are, and then actually allocating funding towards those research programs.

IRA FLATOW: That seems crazy.

PATTY KAISHIAN: It is a little crazy.

IRA FLATOW: If something is so essential to how nature works and we don’t understand it, that’s kind of nuts.

PATTY KAISHIAN: Yeah, I know. I think so too.

IRA FLATOW: Well, I’m glad that you’re working on it at least.

PATTY KAISHIAN: Yes. Yeah, it’s been fun. And as I mentioned, the tide is starting to shift a little bit. My college students have expressed a lot of interest in fungi. And I see that interest growing. So I’m hopeful that more mycology programs are going to start to pop up, and there will be more chances to study them and more funding available. So I think we’re heading in the right direction.

IRA FLATOW: That’s great. So you see, fungi is not so scary once you get to know them.

PATTY KAISHIAN: Yeah, once you get to know them, they’re pretty nice.

IRA FLATOW: Patty, thank you for taking time to be with us today.

PATTY KAISHIAN: Thanks for having me. This was great.

IRA FLATOW: Dr. Patty Kaishian is a mycologist and visiting professor of biology at Bard College in New York’s Hudson Valley.

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