How Did ‘The Last of Us’ Outbreak Start? The Fungus That Makes People Attack Each Other Exists in Real Life

Sophie Hanson
The Last of Us
Photo: Liane Hentscher/HBO

Warning: This article contains spoilers for The Last of Us. HBO’s thrilling new post-apocalyptic series is set 20 years after a global pandemic decimates much of the human population, but this isn’t like any disease we’ve ever seen before. So how did The Last of Us outbreak start?

In the first episode that aired on Sunday, January 15, 2023, the show delves deeper into the outbreak’s origins than the Naughty Dog-developed video game on which the series is based. The opening scene shows two epidemiologists speaking on a talk show in 1968, speculating about significant viral threats to human existence. One says viruses akin to the flu, which another, Dr. Newman, disagrees. “Mankind has been at war with the virus since the start sometimes millions of people die as in an actual war. But in the end, we always win,” he explains, adding that fungus will be humanity’s undoing “in the most dire terms” and alludes to how it might begin. This scene is pivotal to explaining how the outbreak in The Last of Us begins.

How did The Last of Us outbreak start?

How did The Last of Us outbreak start? The disease that wipes out most of humanity in The Last of Us is a fungus—a mutated microorganism known as cordyceps, which actually does exist in real life, but it can’t infect humans. Yet, at least.

The Last of Us

Liane Hentscher/HBO

In the opening sequence of episode one, Dr. Newman explains: “Fungi seem harmless enough, but many species know otherwise because there are some fungi that do not seek to kill but to control… Viruses can make us ill but fungi can alter our very minds,” citing the illicit drug LSD as an example, which is derived from psilocybin, a naturally occurring psychedelic prodrug compound produced by more than 200 species of fungi.

“There’s a fungus that infects insects, it gets inside an ant, travels through its circulatory system to the ant’s brain and then floods it with hallucinogens, thus bending the ant’s mind to its will. The fungus starts to direct the ant’s behavior, telling it where to go, what to do like a puppeteer with a marionette and it gets worse.”

He continues: “The fungus needs food to live. So, it begins to devour its host from within replacing, the ant’s flesh with its own, but it doesn’t let its victim die. It keeps its puppet alive by preventing decomposition. How? Where do we get penicillin from?” he asks, referencing the groundbreaking antibiotic that was first discovered in moldy bread.

The other epidemiologist interrupts, saying that this sort of fungal infection is real but not in humans. “True,” says Dr. Newman, “fungi cannot survive if its host’s internal temperature is over 94 degrees. And, currently, there are no reasons for fungi to evolve to be able to withstand higher temperatures. But what if that were to change? What if, for instance, the world was to get slightly warmer?” he challenges, which foreshadows the modern-day climate crisis.

The Last of Us

Liane Hentscher/HBO

“Now, there is reason to evolve,” he continues and rattles off a number of fungi that could mutate to become capable of “growing into our brains and taking control, not millions of us but billions. 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. And there are no treatments for this, no preventatives, no cures, they don’t exist.”

“So, if that happens—” the talk show host begins. “We lose,” replies Dr. Newman bluntly and an ominous soundtrack kicks in as viewers come to terms with a possible end-of-days. The show will predicably explore exactly how the outbreak starts but we don’t have information on that yet. The games, however, may provide clues.

In the prologue to The Last of Us: Part I, you can find a newspaper that outlines the cause of the outbreak. In the video games, it was primarily caused by crops contaminated with fungus. People ate food with enough traces of cordyceps to become infected and lost their minds to it. The infection spreads either by being bitten by someone already infected or by inhaling airborne spores from dead infected that would fill the air.

The show has deviated from the game in that regard. The airborne spores that required gas masks to navigate are gone and instead, we have tendrils (which, by the way, will make your skin crawl from a visual perspective), potentially given the real-life COVID pandemic wherein a mask helps slows transmission.

The Last of Us

Liane Hentscher/HBO

During an interview with Collider, the show’s creators Craig Mazin (Chernobyl) and Neil Druckmann (president of Naughty Dog) explained that they wanted to make the infection as based in science as possible. “Cordyceps is a fascinating concept, and it’s absolutely real,” Mazin explained. “We wanted to push that a little further. We wanted to give us much reality as we could because the realer that is, the more we connect to the characters that are in that space playing around.”

Druckmann added: “With the more recently infected, we had a lot of conversation about what that vector could look like because there are certain things from the game that we took away. The game had spores in the air and people had to wear gas masks, and we decided, early on, that we didn’t want to do that for the show,” he said. “Eventually, those conversations led us to these tendrils. And then, just thinking about how there’s a passage that happens from one infected to another, and like fungus does, it could become a network that is interconnected. It became very scary to think that they’re all working against us in this unified way, which was a concept that I really liked, that got developed in the show.”

Mazin continued that the audience is more knowledgeable about pandemics these days than they were when the game first came out in 2013. “It was also important for us to acknowledge that the audience is smarter about pandemics than they were five years ago. We don’t want to pretend that they don’t know things,” he said. “And in fact, a lot of the reason this show begins the way it does, with that scene in the ’60s, is to say, “Look, the context is, there are viral pandemics and they are quite dangerous, but there’s something out there that’s worse.” Yikes.

The Last of Us is available to stream on HBO Max. New episodes are released Sundays at 9 p.m. ET. Here’s how to watch it for free.

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