Is The Last Of Us' fungal infection based on reality?

Could Earth really be at risk from a deadly fungal infection?

  • The Last of Us brings the hit 2013 PlayStation game to life as a nine-episode series

  • The show explains the zombie apocalypse with an opening that doesn’t appear in the source material

  • Although fictional, the first episode warns that Cordyceps Brain Infection (CBI) could happen in real life

  • Showrunner Craig Mazin and Executive Producer Neil Druckmann have explained how the outbreak is based on real-life science

Pedro Pascal as Joel Miller in The Last Of Us. (Sky/HBO)
Pedro Pascal as Joel Miller in The Last Of Us. (Sky/HBO)

Adapting video games into live-action has never been easy, but as Craig Mazin’s The Last of Us soars to the top of the charts amid claims it’s the greatest adaptation of all time, it’s clear the Chernobyl director is doing something right.

Telling the story of Ellie (Bella Ramsey) and Joel (Pedro Pascal) in the year 2033, The Last of Us navigates a seemingly fictional apocalypse where humans are turned into zombified mushrooms by a strain of the Cordyceps fungus.

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The Cordyceps brain infection (CBI) might sound fanciful, but as the first episode warns, it’s entirely possible. So, what does The Last of Us get right about the zombie apocalypse and could it happen in real life?

A warning about Cordyceps

While Naughty Dog’s The Last of Us starts in the middle of the Cordyceps outbreak in 2013, the series opens with a flashback to 1968. There’s a surprise cameo from The Mummy’s John Hannah as epidemiologist Dr. Neuman, who discusses how the ongoing war between the human race and infections won’t end with a virus… but a fungus.

Neuman says that the fear of a viral pandemic doesn’t keep him up at night, but if a fungus were able to evolve, it could take hold of humans and use them as a host. Viruses can make us ill, but fungi can “alter our very minds.” He gives the example of a particular species of ant and a “zombie” fungus that puppeteers the host like a marionette. Ultimately, the fungus devious it from within. It’s pretty gruesome stuff that’s left some viewers thinking since its debut.

Cordyceps fungi on a wingless insect
Cordyceps fungi on a wingless insect (Getty)

Speaking to HBO’s official The Last of Us Podcast, Mazin explained how the original opening to the series would honour David Attenborough’s Planet Earth and a famous segment on how the real-life Cordyceps works. In the end, Neil Druckmann felt it was “boring” because it was too much like a school instructional video. Still, some form of explainer was needed for those who haven’t played the game before.

Instead, we get Neuman’s grim foreshadowing of a fungi-controlled race with one goal “to spread the infection to every last human alive.” It ends with the kicker that there are no treatments, no preventative measures, and no cure.

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Those who remember the game will know this could have huge ramifications for Ellie's role and how the series evolves.

The science behind The Last Of Us

Bella Ramsey as Ellie Williams & Pedro Pascal as Joel Miller in The Last Of Us. (Sky/HBO)
Bella Ramsey as Ellie Williams & Pedro Pascal as Joel Miller in The Last Of Us. (Sky/HBO)

Back in 2013, Druckmann told Mashable the science behind the original story and how he and Game Director Bruce Straley researched the likes of Cordyceps and the Costa Rican Hymenoepimecis argyraphaga wasp that uses a spider to host its eggs.

During his Mashable interview, Druckmann said he’d read a book called The Last Plague that charts the 1918 Spanish Flu. He talked about how towns were shut down to avoid infection, adding, “It makes you really wonder, 'What will I do to survive?'" In 2023, there’s an added sense of poignancy to his words following the coronavirus pandemic.

Returning to fungi, Druckmann said, "It was all based on the idea that the more numerous a species becomes, the more likely it is to be preyed on by this fungus.” Neuman’s opening speech relates to the real-life Ophiocordyceps unilateralis that’s better known as the “zombie-ant fungus.” The mortality takes up to 10 days and also includes a process where tendrils grow from the ant’s head to release spores and help the fungus spread.

This fungus can turn the ants into zombie
This fungus can turn the ants into zombie. (Getty)

The premiere later features tendrils sprouting from Nana Adler’s mouth on Outbreak Day. This in itself is a change from the games, with Mazin telling how the airborne spores have been swapped out for tendrils. As well as being closer to the actual science of Ophiocordyceps unilateralis, it gets around the problem of everyone having to wear gas masks for every scene in 2033.

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As for Neuman’s worries, he says that while fungus hasn’t evolved to survive beyond its host having an internal temperature of 34C (below the human average), an increase in the Earth’s temperature could trigger it. It’s a clever wink at climate change. Mazin fact-checked the first episode with The Hollywood Reporter and explained his own take on the real-life science.

LOS ANGELES, CALIFORNIA - JANUARY 09: (L-R) Craig Mazin, Bella Ramsey, Neil Druckmann, Pedro Pascal, Chairman/CEO of HBO & HBO Max Casey Bloys, and EVP, Head of Drama, HBO Programming Francesca Orsi attend HBO's
(L-R) Craig Mazin, Bella Ramsey, Neil Druckmann, Pedro Pascal, Max Casey Bloys, and Francesca Orsi attend HBO's The Last of Us LA Premiere. (Jeff Kravitz/FilmMagic for HBO)

Comparing The Last of Us opening to the Chernobyl Nuclear Plant blowing up, Mazin added, “Right now, there’s something that’s just waiting to blow up — you just don’t know about it.

"It was so upsetting to say to people, ‘We knew about this, it’s been there, now we’re gonna show you the night it finally happens.’ Not suddenly, but finally.”

Could The Last of Us really happen?

Bella Ramsey as Ellie & Pedro Pascal as Joel in The Last of Us. (Sky/HBO)
Bella Ramsey as Ellie & Pedro Pascal as Joel in The Last of Us. (Sky/HBO)

2013’s The Last of Us was terrifying because it wasn’t your standard zombie game where the human race was obliterated by a manmade outbreak from some villainous genetics company. Like Danny Boyle’s 28 Days Later reinvented the zombie movie genre with its fast zombies, The Last of Us brought something new with its mushroom-covered infected.

Similar to how 28 Days Later’s zombie outbreak was started by an infected monkey, the idea that we could be wiped out by evolving fungi is an interesting one. Would we really end up as mutated monsters clawing our way through the ruins of a city though? Thankfully, this dystopian future is one that Mazin doesn’t think would play out exactly like the series as he concludes, "Would they do exactly to us what they do to ants? I don’t think so. I doubt it."

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The Last of Us has several stages of infection, with us only really seeing the first stage, known as Runners. If you were looking (very) closely at the final shot of The Last of Us premiere, you’ll spot a Clicker-stage infected atop the ruins of Boston. The trailers have largely focused on the human side of the story, although the appearance of a Bloater infected emerging from a fire has become synonymous with the series.

A screenshot from The Last Of Us on PlayStation 3. (Naughty Dog/Sony PlayStation)
A screenshot from The Last Of Us on PlayStation 3. (Naughty Dog/Sony PlayStation)

While you can probably sleep a little easier that you won’t start sprouting mushrooms, Professor David Hughes — who actually consulted on 2013’s The Last of Us — has some wise words. A decade after the first game came out, Hughes told Esquire how we haven’t developed the right arsenal against fungi because it’s more closely related to humans than plants. Whatever kills the fungus would kill us. Ants can largely control the Cordyceps infection because they just wall off the infected, however, would humans be as willing to make that sacrifice?

As a glimmer of hope, Ophiocordyceps unilateralis only affects one ant species, so we can’t necessarily apply it to humans.

We’re going to find out Cordyceps takes hold in The Last of Us, but safe to say, Hughes’ musings that the Salem Witch Trials could be to do with hysteria involving infected grain might not be far off the mark.

We’re still a long way off from the human race being overtaken by rogue mushrooms, but as The Last of Us opening, Planet Earth, and various scientists have shown, it’s not entirely impossible.

We’ll never look at shiitake mushrooms the same again.

The Last Of Us is on Sky Atlantic and streaming service NOW with an Entertainment Membership for just £9.99.