HBO’s adaptation of The Last of Us premiered last week, and for the wellness hags among us who never played the astronomically best-selling video game, it brought an unsettling surprise. The season opener leads with a mid-century scientist explaining why it isn’t viral or bacterial pandemics mankind should fear (covid, a mere glint in his eye), but fungal. Fungi, he says, don’t parasitize humans because our body temperatures aren’t favorable to them—yet. Should the planet warm a few degrees, he foreshadows gloomily, that could all change.
He name drops one fungus in particular, and if you’ve ever sipped on a functional seltzer or stirred some Moon Juice powder into your smoothie, you might recognize it. The cordyceps mushroom is the villain of HBO’s show, and it’s not spreading via the Whole Foods supplements aisle. In The Last of Us, ghastly tendrils of the stuff grow out of the mouths of infected zombie-like people, who violently flail about in search of hosts to bite, or kiss to death, thus spreading the fungi. Is it fictional? Sure. Does it make me think twice about pounding adaptogenic lattes that, ironically, claim to decrease my mortality? Absolutely.
Mushrooms are having a banner decade. Everyone and their great aunt is microdosing psilocybin. Bjork and Margo Price both have mushroom albums. You can’t swing a reusable tote in the health food store without knocking over a grow-your-own porcini kit. And, in certain circles, words like chaga, lion’s mane, and reishi are becoming as familiar as Oatly.
But The Last of Us buzz has people spooked, asking different versions of “Will my creminis make me eat my friends?” I woke up the morning after watching the first episode and Googled “Should we stop eating cordyceps?” I got no results, and had a lot more questions. How could something that supposedly helps us live longer also turn us into the undead? Is the wellness industry giving pathogenic fungi a leg up by cultivating them en masse? And where is Big Mushroom in all this? (You know the Got Milk people wouldn’t stand for an HBO show about a dairy-fueled apocalypse.) Neither the mushroom lobby nor Moon Juice responded to my requests for comment, which left me no choice but to dig into the science.
If the idea of a zombifying fungus sounds vaguely familiar, then you might have been getting stoned and watching Planet Earth back in 2012, when David Attenborough first terrified the world with the revelation of mind-control mushrooms. Over a droning string waltz, Attenborough explained how cordyceps infects ants and manipulates them into climbing to a high branch, sprouting a mushroom out their backs, and making it rain infectious spores on all the unsuspecting ants below. The fungus does this by bypassing ants’ brains entirely, controlling their muscles in a coup reminiscent of Robocop’s fourth prime directive—and The Last of Us is effectively saying we’re next. But are we?
“Cordyceps are mostly all insect pathogens, and although insects are animals, they’re pretty far away from us,” Matt Kasson, a mycologist from West Virginia University who studies, get this, zombie cicadas, told me. “The likelihood of something jumping from an insect to a human is pretty low,” he added. (The show suggests that the fungus leapt to humans from flour in an Indonesian grain mill.)
Jason Stajich, a professor of plant pathology at University of California, Riverside, agreed with Kasson: “If you’re gonna get inside the [human] body and do stuff, you’ve got to be able to survive at 37 degrees celsius and, of course, evade the immune system.” (Show me that video game.) What our immune systems and body temps don’t kill, our stomach acid will—and if you’re wondering how something that can’t even live in our bodies could possibly be good for them, ditto, but the scientists assured me even dead mushrooms have health benefits.
“If you want to play the sci-fi card a little bit, though,” Stajich continued, “there are compounds that fungi make that cause behavior changes in human hosts.” Like ‘shrooms??? I asked, ever the unfortunate younger sibling. “Yes,” he agreed, graciously, “and also ergot, the fungus tied to the Salem Witch Trials.”
But ergot targets the liver with poisonous toxins, something cordyceps aren’t capable of. And psilocybin works its magic by helping the brain switch between activity states—a fun high, to be sure, but not one that’s going to make you eat people.
It turns out the adaptogens we stir into hot chocolate and golden milk have very little in common with the cordyceps that, in The Last of Us, make us eat people. Despite climate change, they haven’t evolved to thrive at higher temperatures yet—but even if they did (which certain fungi have been known to do, as anyone who suffers from mid-summer thrush knows), they’re still not likely to spread via zombie apocalypse. Why? Because, if a person were to become infected and turn into an undead carrier, humans (unlike bugs) wouldn’t just leave them lying on the forest floor.
“Even if there was a fungus that could erupt out of your face,” Kasson said, “it’s not like there’s a bunch of human cadavers lying around that we’re gonna watch to see the progression of microbes on their skin.” Some fungi may produce fruiting bodies on deceased humans, he conceded, but we don’t keep them uncovered long enough to see that.
And the transmission method wouldn’t be nearly as voracious as it is in The Last of Us. The infected, as they’re called on the show, exhibit signs of something Stajich calls “active host transmission,” where the host becomes aggressive. The cordyceps-fueled ants in the Planet Earth clip, on the other hand, are textbook passive hosts. They don’t sneak up behind other ants or spew mycelia at them; they just climb a branch and die alone.
Unfortunately, being safe from a cordyceps apocalypse does not mean we’re in the clear from other fungal pathogens in a warming world.
“There’s certainly a number of fungi that can grow above 37C…that will ravage a human,” Kasson said. Ravage. Cool. While these have mostly only shown up in immunocompromised people in the past, that’s beginning to change. One, called candida auris, is now emerging in hospitals globally; one scientist told me that it “came out of nowhere.” While it used to only infect sick people, it’s now possible for healthy people to catch it, and it needs only an open wound to infect the bloodstream and affect vital organs.
Another, called coccidioides and pronounced god-knows-how, thrives in the soils of the southwestern United States and causes a pneumonia-like infection called valley fever, the incidence of which is on the rise as the region gets dryer. Still another showed up in Joplin, Missouri, in 2011, when a tornado kicked up a fungus called necrotizing mucormycosis, the spores of which got in people’s cuts as they dug through the storm’s wreckage. Treatments were ineffective and five died.
“Finding ways to treat fungi that don’t harm humans is challenging,” Kasson said, “because a lot of the things we use to kill off fungi could harm us.” That’s why treatment resistance is a key predictor of fungi’s ability to spread, as is their ability to affect immunocompetent people and pass from person to person. In a flashback to the early days of the outbreak in The Last of Us’s second episode, we see a mycologist in Jakarta tell the military: “There is no medicine. There is no vaccine. Bomb this city and everyone in it.” Again, cool.
The mycologists I spoke to were quick to point out that fungi have caused extinctions in several dozen frog species, and are currently threatening extinction events in salamanders and bats. (And they’re certainly not doing the ants any favors.) It’s also now widely accepted in the scientific community that mankind exists because of a fungal bloom after the Cretaceous period that favored mammals over reptiles.
Here in the Anthropocene, six states have now legalized human composting—which involves being buried in a fungal suit that digests your body after you die. The tl;dr? Drink your hippie latte. One way or another, the mushrooms get us in the end.
Linni Kral is a writer, editor, and educator based in Brooklyn, NY, whose work has been published in The Atlantic, Slate, The Village Voice, Atlas Obscura, Marie Claire, and Condé Nast Traveler, among others. For more of her thoughts on food, science, or the end of the world, visit linnikral.com or follow @linnikral.