In typical zombie apocalypse stories, like The Walking Dead, World War Z and Train to Busan, a virus quickly transforms people into bloodthirsty monsters. But The Last of Us, a new HBO show based on a video game of the same name, bucks convention in a couple of ways.
For one, the pathogen-carrying human hosts are not “undead”—they’re still alive. And it’s not a virus that’s infected them, but rather, a fungus.
What’s more, the fungus exists in real life. The game’s creators have said they were inspired by a segment from the BBC’s “Planet Earth” documentary series in which a fungus takes over the mind of an ant.
Some parts of the show are, of course, fantastical. The apocalyptic takeover of the human species by a mind-controlling fungal pathogen is implausible, David Hughes, an entomologist at Penn State University who advised on the video game, tells the Washington Post’s Kasha Patel.
But other parts are inspired by real science, as well as ideas about climate change and disease that scientists are grappling with today.
In the “Planet Earth” clip that inspired the game, an Ophiocordyceps fungus infects a bullet ant, writes Vox’s Benji Jones. The fungus grows inside the insect, turning about half its body into fungus. But it leaves the ant’s brain intact, allowing it to manipulate the insect’s behavior. Ophiocordyceps directs the ant to climb a branch, where it dies. Then, the fungus grows from the ant’s head, enabling it to effectively spread spores and infect more hosts.
Thirty-five known Ophiocordyceps species can influence the behavior of insects, and experts estimate that hundreds more have yet to be discovered, João Araújo, a mycologist at the New York Botanical Garden, tells CNN’s Kate Golembiewski.
But scientists aren’t concerned about these fungi infecting humans. “They’re super species-specific,” Charissa de Bekker, who studies “zombie ants” at Utrecht University in the Netherlands, tells CNN. And humans have very different bodies from these insects.
Still, a few themes the show hits on are relevant to scientists today. One is that fungal infections in humans are relatively understudied and difficult to treat. While we inhale fungal spores with every breath we take, most of them are harmless, de Bekker tells Vox. Of the 1.5 to 5 million fungus species, humans only become ill from a few hundred of them, which mostly threaten immunocompromised people, writes the Post.
But more than 300 million people around the world get a serious fungal infection annually, and about 1.5 million of them die, reported Wired’s Rose Eveleth in 2021. Part of what makes these infections deadly is that they can be difficult to treat.
“Fungi are more closely related to animals than they are plants,” Kasson tells the Ringer. “It’s hard to combat them without combating ourselves. So, they have to come up with specialized types of compounds that can kill the fungi without harming the host.”
“Humanity should be investing more in learning about what is the largest kingdom on the planet,” Arturo Casadevall, a microbiologist at Johns Hopkins, told Wired.
The Last of Us also suggests that part of what primed the planet for the fungal takeover is its warming temperatures. Most fungi prefer temperatures lower than those of the human body, de Bekker tells Vox. The show posits that as fungi adapt to a warmer planet, they could be better suited to infect humans. Scientists are already considering this theory.
“It’s not outlandish, the argument that global warming has increased the thermal tolerance of a fungi,” Ilan Schwartz, who studies invasive fungal infections at Duke University, tells Vulture’s Roxana Hadadi. “It hasn’t been proven. It’s a hypothesis, and it’s happening on a fairly slow scale. … But it is possible.”
For one, the fungus Candida auris, which is resistant to some antifungal drugs and threatens people with weakened immune systems, is theorized to have adapted to humans’ body temperature, per the publication.
But don’t panic: A widespread fungal pandemic is unlikely because of how the infections spread in humans, Dimitrios Kontoyiannis, a mycologist at the University of Texas, tells CNN.
“There’s lots of serious concerns in the world, but this isn’t one of them,” Schwartz says to Vulture, regarding the show’s premise.
But the current global pandemic could increase the risk that humans face from fungal foes.
“Maybe a larger portion of the population will be immunocompromised due to things like Covid-19 and other viruses that may predispose us to subsequent invasion by these generally pervasive fungi,” Kasson tells the Ringer.