HBO’s series adaptation of the video game The Last of Us has spread like a virus. Every week, we watch as Joel and Ellie journey through a post-apocalyptic wasteland, one that is infested with terrifying zombie-like humans.
Those who’ve played the game know that the brain-dead creatures from The Last of Us are technically not zombies. Zombies belong to the world of the undead. They’re corpses that are brought back to life but lack the ability to speak or even walk properly. Meaning, mythologically speaking, you’d have to die first to be a zombie. But in The Last of Us, you’d have to be alive to be infected and become host to the fungus that wreaked havoc in the game’s immersive world.
We’re still reeling from the effects of the COVID-19 pandemic—which is far from over, by the way—so a lot of us are wondering the same thing: Should we be worried about a fungal pandemic, too? How sound is the science in The Last of Us? Let’s see what the experts say.
How Fungal Pandemics Happen, in The Last of Us and IRL
So far, The Last of Us series has stayed close to its source material, save for a few deviations that showrunners Craig Mazin and Neil Druckmann made. One of those changes is pretty major—how the fungus that causes an apocalypse begins to spread.
(Spoilers to follow!)
In the first episode’s cold open, we travel back in time to a talk show in 1968. The guests are epidemiologists warning the public of global pandemics. But one of them reveals that he fears it will neither be viruses nor bacteria that will cause sickness all over the world, but fungi. Yes, the kingdom of eukaryotic organisms to which mushrooms belong.
“Fungi seem harmless enough. Many species know otherwise because there are some fungi that seek not to kill but to control,” the scientist explains. “Viruses can make us ill but fungi can alter our very minds.” He mentions LSD whose hallucinogenic effects come from the fungus ergot. And very ominously, he warned the public of fungus known to infect insects, control their brain, and eat the hosts from within until it can find another host.
The first episode of The Last of Us sets up the origin of the fungal disease that has plagued its fictional world since 2003. And two decades later, the people who managed to survive think that the pandemic started from mutated cordyceps, one of the many genera of fungi known to man. It’s also the parasitic fungi described by the epidemiologist.
Thankfully, The Last of Us is not real life…yet. And the creators of the game and the show got a couple of details inaccurately. For one, cordyceps are not the pathogenic fungi that scientists once believed. More recent research has made a distinction between cordyceps and ophiocordyceps, a different genus of fungi. The parasitic mushrooms described in the show are closer to the ophiocordyceps genus, specifically the specie ophiocordyceps unilateralis. They’re more commonly known as zombie-ant fungus because they infect insects like ants and control their behavior very much like the way the epidemiologist described.
Like the infected in The Last of Us, this fungi specie spreads spores to increase infection after it has devoured its current host. Even if he got the classification wrong, it’s a pretty neat concept that Neil Druckmann developed in the game he co-created. He revealed that the idea was inspired by a clip on Planet Earth that featured the zombie-ant fungus. He wanted to explore what might happen if genes of this fungi mutated and allowed spores to infect bigger hosts, like humans.
Joel explains to Ellie, a pandemic baby, that spores of the deadly fungus spread onto basic food like flour. Almost every country consumes flour which explains how the disease spread quickly and successfully in The Last of Us. But this is another creative liberty that the game and the show have taken. In real life, fungi like the zombie-ant parasite aren’t able to take on such big hosts as humans.
An assistant professor of biology from the Utrecth University, Charissa de Bekker, further describes ophiocordyceps as “super species-speficic”. She adds, “They have very refined machinery to interact with their hosts and do these really interesting things like changing behavior, but they can’t jump from one species to the next.”
Humans are pretty far from insects as far as the animal kingdom goes, and the biggest advantage we have is our body heat. We’re simply too warm for parasitic fungi to thrive in let alone control completely. Fungi do infect humans but not in the way The Last of Us presented.
Should We Be Afraid of Fungi Taking Over Our Minds and Our World?
The short answer is no. Unless you’re a small insect you probably have nothing to worry about in this lifetime. But scientists aren’t ruling a fungal pandemic out as an impossible event.
The thing about living things is that they evolve. Organisms want to live longer so they can produce more offspring and survive as a species and as ecosystems. Even fungi adapt to their ever-changing environment, which scientists are already observing in nature. “Fungi will adapt to warmer climates by developing greater heat tolerance,” says microbiologist Arturo Casadevall. “Some will then be able to grow at human temperatures and cause new fungal diseases that we have not seen before.”
It might take some time—millions of years, in fact—but there is a future where a fungal pandemic can happen. Maybe not in the turn-humans-into-brain-dead-clickers type of way like in The Last of Us but more similar to the viral pandemic we’re still living in now. Serious fungal diseases can also attack our immune systems and make us susceptible to other illnesses, like fever and pneumonia, very similar to how the coronavirus manifested in the early days of the pandemic.
And with global warming continuing at an escalated pace, we might be creating an environment in which fungi like ophiocordyceps unilateralis can adapt to hotter temperatures. When that happens, though it probably won’t in our lifetime, The Last of Us is going to look like a doomsday prepper’s instructional video than a compelling yet far out piece of television.