The People Who Study Fungus Know Why It’s Suddenly Taking Over Horror

HBO’s smash-hit adaptation The Last of Us is the latest in a string of horror stories featuring fungi as the source of fear. The zombie-like outbreak that takes place in the show, which is based on the dystopian video game series of the same name, stems from a mutated version of a parasitic mushroom which fictionally evolves to attack humans instead of insects.

But this unique take on zombies isn’t alone in creating a frightening representation of fungal attacks. Two recent novels both take inspiration from more virulent forms of mushrooms. In Mexican Gothic, by Silvia Moreno-Garcia, the narrator knows something isn’t right with a family and their mansion, and soon discovers an intergenerational secret intertwined with a mycelium network. In last year’s What Moves the Dead, by T. Kingfisher, it’s a mycologist who discovers the root of the town’s sudden mysterious illnesses.

Should we be worried? Says mycologist Dr. Andrew Miller: "Not yet."

Science-fiction’s fungal fascination goes back much farther. In William Hope Hodgson’s 1907 short story “The Voice in the Night,” which has inspired multiple screen adaptations (including one by Godzilla’s Ishirō Honda), a shipwrecked couple is slowly consumed by a fungal growth. The carnivorous ooze in the 1958 cult horror The Blob was inspired by a slime mold, originally classified as a fungus. There are even two separate episodes of The X-Files, which is sci-fi horror’s version of “The Simpsons did it”: a 1994 “Monster-of-the-Week” plot centered around a lab-developed, silicon-based organism that behaved like a Cordyceps, and a 1999 episode in which a giant mushroom attacks via hallucinogenic spores.

It’s not just horror plots that fungus is working its way into. With the increased focus on decriminalizing psilocybin as treatment for addiction, PTSD, and other mental health disorders, mushrooms have slowly begun to worm their way into popular media and news stories. They’ve been explored as building materials and an alternative to pesticides and even meat.

But of all the roles mushrooms have been cast in, the one that seems to captivate our collective attention the most is the villain. Which brings us to the question: With all the portrayals of how fungi and their fruiting bodies might attack or kill us, do humans have cause for concern? Not really, according to Dr. Andrew Miller, senior principal mycologist of the Illinois Natural History Survey and director of the herbarium/fungarium at the University of Illinois. “At least, not yet.”

In most of these portrayals, it’s not just death that’s at stake, it’s transformation. The moment of real terror in any classic zombie flick is realizing that the person you love is certainly doomed, and that you must turn on them before they turn on you. The Cordyceps in The Last of Us has a similar mirroring ability to turn us evil, but it’s not only the infected who fall prey, as seen in the series’ most recent episode. When driving through what’s left of Kansas City, Missouri, it’s fellow humans, not the infected, who become the biggest threat to Joel and Ellie’s safety. Melanie Lynskey’s cold-blooded resistance leader shows us that there is more than one way to “turn” in a dystopian future.

Humans are well-protected from most noxious fungi species, including Cordyceps, by our high internal body temperature. Very few species can tolerate 98.6 degrees Fahrenheit. So why do so many stories find something to fear in our fungal friends? In part, it’s the need for a fresh take on the viral and bacterial infection stories we’ve already seen countless versions of, an example of sci-fi writers on the hunt for something new. But there’s something else about fungus that makes it tempting for fiction—our own limited understanding.

Though often confused with plants, fungi are a separate kingdom from flora or fauna. “Fungi are more closely related to animals than they are actually to plants. We just have historically always taught them alongside botany,” says Miller. “That’s why it’s actually difficult to fight fungal disease in humans.”

Because of our shared traits, creating a medicine that attacks just a fungus without also attacking our own systems is challenging. But even with our similarities, we don’t have a great understanding of fungi overall. Mushrooms alone are the second most common eukaryotic organism in the world—only topped by insects—with numbers estimated to be anywhere in the range of 700,000 to 10 million species, according to Miller.

Beyond mushrooms (which are only the fruiting body of the mycelium stretching through the surface beneath them), DNA sequencing has led to the discovery of things called “dark taxa.” These bits of mycelium are lurking underfoot in our soil and sometimes on plants. For unknown reasons, they don’t try to reproduce or fruit. But underneath our feet, hundreds of thousands, if not millions, of species of mycelium are existing quietly and contentedly, according to Miller. We don’t know why they’re content to not fruit, or what makes them suddenly want to.

One of the more accurate notions in The Last of Us is the idea of fungi evolving to adapt to climate change. Last week, the Wall Street Journal reported that more than 7,000 people in the U.S. died of fungal infections in 2021, up from hundreds a year around 1970. It takes time for evolution to produce observable results and then more time to prove it in academic papers, but anecdotal evidence of changing habits and habitats are popping up in studies. Mycologists have been able to map one species, Amanita thiersii, as it has migrated from its origin in Texas in the 1960s and slowly spread northward over time. It can now be found as far as northern Illinois.

Parasitic fungi are changing, too, and while humans might not have cause to worry—yet—other species can’t say the same. White-nose syndrome is a life-threatening fungal infection in bats. First discovered in New York in 2006, it has rapidly made its way across much of North America, causing concern among scientists about vulnerable bat populations. Bats, like humans, are mammals with a typically high body temperature. But during hibernation, their temperature lowers to conserve energy. This change combined with the cooler environment of caves makes them vulnerable to the parasite. Other animal attacks have cropped up, too. A fatal fungal pathogen that infects snakes has been spreading across North America since its discovery in 2008. Miller and his colleagues are also now studying a shell-eating fungus which attacks turtles in the Pacific Northwest.

While it’s possible that Cordyceps or other parasitic mushrooms could one day evolve to survive higher temperatures, it’s not likely to happen any time soon. But many of us have encountered invasive, infection-causing fungal spores. These fungi are not likely to cause a world-ending event, but they can be dangerous and even deadly. Three types of infections caused by fungus—histoplasmosis, blastomycosis and coccidioidomycosis—are common throughout most of the United States. Many, if not most, of us have already breathed such spores into our lungs, where they become calcified and remain indefinitely. But for some groups, these infections can be severe, even leading to death in some cases.

“Most people don’t know that if you’ve visited Arizona, you have coccidioidomycosis in your lungs,” says Miller. “They don’t tell you that at the Welcome Center.” If you’ve ever been in a cave, histoplasmosis is probably present as well.

In The Last of Us games, it’s spores that spread the Cordyceps infection with terrifying reach. The toxicity is so dense that merely being outside requires the characters to wear a gas mask. (The showrunners made the adaptation decisively less accurate for the purpose of seeing characters’ faces. On behalf of fellow Pedro Pascal fans everywhere, I thank them.) The ability of spores to spread across enormous distances is a large reason mushrooms have become so prolific. It also adds to their unsettling nature. “We’ve found spores up in the atmosphere. They can travel from the U.S. to China and back if they get swept up in large wind patterns,” says Miller. But even in their far travels, it’s not likely they would actually survive the journey. Most spores stay localized or rely on animals to assist in their spread.

Mycelium is another of mycology’s creepier features: large underground mycorrhizal networks that are able to stretch miles. The real-life underground networks inspired part of the plotline in The Last of Us. The moment in Episode 2 when a hypha twitches and Joel knows that more infected will be on their way—that’s the mycelium network at work. But a “hive mind” communication like the show presents isn’t firmly based in science. Some ecologists have hypothesized that trees may use the network to communicate with each other and live in cooperative communities, but many scientists believe the idea to be misleading.

That’s not to say there isn’t some form of network present. The mycelium can pass food along, even from trees to plants, such as in the elusive and often misattributed plant species Ghost Pipe. For a mysterious plant without chlorophyll to photosynthesize its own food, the mycelium is a literal lifeline. Comparatively, the moment we see the hypha enter Tess’s mouth, a more sinister feeding—or perhaps initiation—takes place. But even though we don’t know the full capabilities of mycelium, large-scale communication is still likely a stretch. Considering the number of “dark taxa” Miller describes, that should be a sigh of relief for humans.

Some mycologists have taken to social media to protest the negative portrayal of our neighbors in the natural world, pointing not only to the misrepresentations but also to the fact that fungi are hardly the most threatening adversary in light of climate change, war, and other illnesses.

Despite how far-fetched it is, Miller says he doesn’t really mind the connotation behind the show: “We’ve had such limited media experience with fungi. We’ll take anything.” His personal favorite mushroom-inspired plot is The Beguiled, in which Southern women entice and attempt to poison Clint Eastwood’s Union soldier character with a mushroom.

But he does wish people would remember all the ways in which fungus can enrich our lives. Baking and brewing depend on yeast. Not to mention the lives saved by penicillin.

“All the bread we eat and beer we drink is thanks to a fungus,” says Miller. So enjoy some sourdough and a nice IPA while you cozy up for the next episode of The Last of Us. Just don’t worry … too much.