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The Fungus that Reduced Humanity to The Last of Us

The views expressed are those of the author and are not necessarily those of Scientific American.

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Screenshot from The Last of Us

Pop culture is again in the quickly decaying grasp of a shambling horde. For how many times zombies have appeared, they rarely have a real scientific reason to. Sometimes it’s a supernatural cause as in Dawn of the Dead. Other times it’s a generic “zombie virus” as in The Walking Dead. In all the attempts to make the dead live again, science usually takes a back seat to the gore—at least until the latest popular iteration of zombies. The Last of Us—a new videogame touted as a masterpiece—has the most scientific explanation for zombies yet, because it uses zombies that actually exist.

Mind Control and Fungus Art

In The Last of Us, 60 percent of humanity is wiped out by the genus of parasitic fungus Cordyceps. Out of the 400 species in the genus, all of these parasites make their homes inside the bodies of others—mostly in insects but some even in other fungi. Not all of these parasites are the evil zombie-makers you might think. A few species of Cordyceps have medicinal value. One of these fungi, Cordyceps subsessilis, has been used to derive immunosuppressive drugs used in organ transplants. But some species of Cordyceps are indeed body snatchers—they have been making real zombies for millions of years.

Ant infected with a cordyceps fungus.

The most cited infestor, Ophiocordyceps unilateralis (previsouly Cordyceps unilateralis), has captured public interest almost as much as zombies have. The fungus famously uses a specific species of ant to complete its life cycle. To live, it must zombify an ant. The consuming fungus forces an ant of the species Camponotus leonardi to get a “death grip” on the underside of a leaf—a position prime for the fungus’ transmission. The poor infected insect—once adorned with a harmless looking spore—then has its tissue slowly eaten and replaced. All that remains of the ant at this point is the exoskeleton, a husk. A deceased ant if there ever was one, save for the spiraling fruiting bodies of the fungus now protruding from the ant’s head and body. These bodies burst forth from the ant, eventually releasing spores ready to begin the cycle anew. (And if you write about Cordyceps, you simply have to include this BBC video showing a time-lapsed infection.)

Other species of Cordyceps are just as transforming, even if they don’t turn the host into a faithful undead servant. Cordyceps ignota infects tarantulas. Its spores burrow into the spider, extending a legion of wispy fingers—collectively known as mycelium—throughout the body. The fingers are how the fungus grows, and how the spider dies. Once the tarantula’s insides are replaced with the fungus, fruiting bodies again burst forth to create art that could only come from such a bizarre demise.

Tarantula infected with Cordyceps ignota.

Real Live Zombies

In The Last of Us, Cordyceps adds humans to the list of hosts. The apocalypse starts when the fungus makes a jump from their typical hosts to humans in presumably the same way some diseases like “swine flu” can jump between species. The new, unidentified species of Cordyceps turns humans first into violent “infected” and then into blind “clickers,” complete with fruiting bodies sprouting from their faces. Like traditional zombie canon, a zombie bite is death. However, the inhalation of Cordyceps spores is the un-death sentence.

The game draws even more inspiration from science than just the name of the fungus. Once a “clicker” completes its cycle, the fungus forces the human into a dark and secluded corner. It is where the human finally dies. Bleeding back into the environment, spores effuse from the corpse to infect again.

An Infected human goes the way of the Cordyceps ant in The Last of Us. By John Sweeney

Without an actual species to pin the apocalypse on, The Last of Us uses a clever combination of Cordyceps attributes. Like the ant-infector, the fungus that brings down humanity turns a host into a drone to eventually do its bidding. And like the species of Cordyceps that turns tarantulas into art, the fictional fungus creates elaborate sprouting bodies off the host. The mix of art design and plausibility gives the choice to model an apocalypse on Cordyceps both scientific rigor and beauty.

I doubt the zombie apocalypse will ever actually happen even it were scientifically plausible. Despite my skepticism, plausibility obviously has nothing to do with why zombies are so popular. They are a fascinating metaphor for our own fear of both death and predators (and who doesn’t like gore-porn?). Scientific plausibility is just icing on the cake. So besides being a brilliant game, The Last of Us is doing science communication. How many people are now searching for more information on parasitic fungi?

Science doesn’t always destroy the horde; it can be another way to burrow deeper under the skin of our favorite fiction. Bring on the zombies, bring on the science.

More Zombies!

Image Credits:

The Last of Us Screenshot (top) and artwork (bottom): The Last of Us™/©2013 Sony Computer Entertainment America LLC. Created and developed by Naughty Dog, Inc,  Artwork by John Sweeney

Ant infected with a cordyceps fungus by Stephen Goddard

Infected tarantula by Ian Suzuki, taken in the cloud forest of Ecuador at the Santa Lucia Cloud Forest Reserve.

Kyle Hill About the Author: Kyle Hill is a freelance science writer and communicator who specializes in finding the secret science in your favorite fandom. Follow on Twitter @Sci_Phile.

The views expressed are those of the author and are not necessarily those of Scientific American.

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Comments 18 Comments

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  1. 1. ckimbrell2 11:28 am 06/25/2013

    My only question is if the clickers eventually die and burst… what exactly are the bloaters?

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  2. 2. EyesWideOpen 4:19 pm 06/25/2013

    What are the bloaters, you ask? “Be careful what you ask for!”

    Bloaters are hosts that swell with the fungus that is keeping them alive because a living host has processes — in humans it’s the endocrine and other systems that secret hormones like serotonin — that cannot be extracted from, shall we say, anything less than living.

    You better hope you’re not a bloater if fungi spores cross species to humans and go airborne. (Evil laughter.)

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  3. 3. rommy 4:38 pm 06/25/2013

    The infection goes sporecloud->runner->clicker->bloater->sporecloud. The author of the article was just using Clicker as the generic term instead of Infected for some reason.

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  4. 4. Algernon Cumbersnatch 6:16 pm 06/25/2013

    I am surprised more of these articles don’t make reference to classic horror stories like “The Seed from the Sepulchre” (Clarke Ashton Smith – click here to read ) or “The Voice in the Night” ( to read).
    Both well worth a read, they only take 5 minutes, but will stick with you for years…

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  5. 5. Bo Knows 7:22 pm 06/25/2013

    “who doesn’t like gore porn” ya, not really!

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  6. 6. Dcode 8:58 pm 06/25/2013

    I see nothing clever or revolutionizing zombie wise, it was well know, and late to the story board for fungus to be the cause of zombie outbreaks. Oh yeah, wouldn’t technically Halo get credited for bringing it into video games? The flood are fungi host on living organisms.

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  7. 7. Kyle Hill in reply to Kyle Hill 10:26 pm 06/25/2013

    I think the clever part was using a fungus that actually existed and actually has mind-control properties. Games like Halo and shows like The Walking Dead always use something generic or unidentifiable. The Last of Us is pretty unique in that respect.

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  8. 8. mustlovescience 12:56 pm 06/26/2013

    As a dedicated fan/analyst of zombies, really enjoyed this fresh take. I’ll add that I think we’re all obsessed with the genre because plays into this very individualistic imagining where all of the random skills we possess that are potentially undervalued would make the difference in our survival.

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  9. 9. thissiteisstupid 4:14 am 06/27/2013

    THEY AREN’T ZOMBIES. Zombies are boring, stupid, overdone, not scary, and completely false beings. This game never ONCE said zombies. It is infected. An undead being would be moving extremely slowly and would NOT be any threat to anything. These are crazy enraged beings that are still alive but mutated. Cut the zombie crap. This game is amazing but it has nothing to do with this stupid zombie Hot Topic crappy phase everyone seems to have. Any movie that isn’t a comedy that is about zombies should not even exist, and neither should you zombie losers.

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  10. 10. thissiteisstupid 5:01 am 06/27/2013

    Zombies are lame and boring and stupid and this game is not a zombie game. It is an infection. I hate you zombie people. Get into real horror and not zombie BS.

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  11. 11. Kyle Hill in reply to Kyle Hill 10:28 am 06/27/2013

    I think it depends on how you define zombie canon. At its heart, or lack there of, zombies are humans who have had their “free will” taken away from them. They are no longer who they were and are motivated by other goals than what would be their own. We describe someone with SARS as “infected,” but we would never call them a zombie. No matter the vector (bite, fungus spore, undead spell), it is turning a human into something else that is true zombification. I think The Last of Us is a great example of that.

    Are you saying that we zombie lovers lack BRRRAAAAIIIINNNNS? (No seriously, be polite)

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  12. 12. Sushin 1:23 pm 06/28/2013

    Frankly the infection in The Last Of Us is bullocks. For one, cordyceps is parasitic and yet you can see it growing all over walls and ceilings in the game. How is that supposed to work?
    I also just don’t buy that the zombies transmit spores with their bites…that doesn’t make sense because it’s a fungus. It needs to create reproductive sprouts in order to spread spores. Is their saliva laces with spores? If a spore was on the zombie at all, simply breathing one in would turn you infected. It’s non-sense…
    And what do they eat? The zombies seem to live forever on nothing. There aren’t enough humans to go around and they aren’t very good hunters to live as long as they do. Considering a human can’t go on living for 3 weeks without food (even less with water) it would only make sense for Cordyceps to kill it’s host (like they do in real life) after driving it to a good location to spread spores.

    I love this game and story but don’t try and tell me the infection makes sense.

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  13. 13. sarah302 1:28 pm 06/28/2013

    To the completely rude and immature people hating on Zombie fans.. heres some news for you. This is the definition of a Zombie: 1. a person who is or appears to be lifeless, apathetic, or totally lacking in independent judgment; automaton.

    You see that last part there? “OR totally lacking independent judgement”. Zombie does not just mean undead coming back to life. 28 days later? I consider that a zombie movie. Those people are not dead, just infected, and cannot control their own actions and attacking their own kind. And stop hating on people for their interests. Really freaking rude and just shows how dumb you really are. Zombies being ‘lame boring and stupid’ is your own opinion. Sorry that you’re missing out on a classic piece of horror entertainment.

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  14. 14. missmuggle 4:39 pm 06/30/2013

    Ok, I just need to let it out somewhere, it probably has a bunch of flaws but it makes sense to me.
    Humans would actually be great hosts for fungi because of our body temperature, which would make the “zombies” in the last of us many times more deadly than zombies like in the walking dead(who get slower in cold times), because they’d have to eat even more to keep the host moving and keep the temperature so the fungus can keep on growing and you know, not die…
    Because mushrooms, and any kind of fungus I guess, like cold places, the warmer and the more wet it is the merrier!(There are some who actually dig cold places but for the sake of the gibberish I’m putting out there I’m going to assume that would not be the case!)

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  15. 15. RecoNFreaK2 10:39 am 02/6/2014

    Does nobody else remember the stalkers from the hotel basement level? Because i do. So this means it’s actually Runner->Stalker->Clicker->Bloater->Spore cloud.

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  16. 16. ERTERT 6:02 pm 08/27/2014








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  17. 17. ERTERT 6:11 pm 08/27/2014


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  18. 18. Andi123 10:31 am 11/18/2014

    The tarantula picture is incredible! Scaryfungus though!

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