Could a parasitic fungus evolve to control humans?
Story by Sarah Gibbens • Yesterday
An ant, no longer in control of its body, crawls away from its colony, hangs perilously on a leaf, and waits to die as a fungus consumes its body, emerges from its head, and releases spores into the air.
Fruiting bodies erupt from a dead moth killed by the cordyceps fungus. The genetically related ophiocordyceps fungus similarly kills insects, but first makes its host body do its bidding.
© Photograph by Alex Hyde, Nature Picture Library
“They’re like these grim little Christmas ornaments out in the forest,” says Ian Will, a fungal geneticist at the University of Central Florida, where these zombified ants can be found.
What if this parasitic fungus could do the same thing to us?
That’s the premise of the new television show based on the video game The Last of Us in which, as a result of warming temperatures caused by climate change, a fungus takes over the world and turns humans into parasite-controlled zombies.
“In a fantastical way, the logical links are there, but it’s not likely to happen in real life,” says Will. But while scientists aren’t worried about fungi evolving to turn people into zombies, rising temperatures do pose a real risk of making fungal infections worse.
How does the parasite infect ants?
Creator of The Last of Us Neil Druckmann was reportedly inspired by a nature video showing the fungus, Ophiocordyceps unilateralis, infecting a bullet ant. Cordyceps are a broad category of insect parasites, and a popular health supplement. But only ophiocordyceps control their host’s body.
About 35 of these ophiocordyceps fungi are known to turn insects into zombies, but as many as 600 may exist, says João Araújo, an expert on parasitic fungi at the New York Botanical Garden.
The first signs of infection are erratic and abnormal behavior. Scientists think the parasite takes physical control of its host by growing fungal cells around the brain that hijack an insect’s nervous system to control its muscles. It’s unclear exactly how it does this, whether by releasing a chemical or altering a bug’s DNA, says Will.
It’s a process the fungus has been refining within its specific host since before human history.
“Our hypothesis is that they have been coevolving for about 45 million years,” says Araújo.
“They’re like these grim little Christmas ornaments out in the forest,” says Ian Will, a fungal geneticist at the University of Central Florida, where these zombified ants can be found.
What if this parasitic fungus could do the same thing to us?
That’s the premise of the new television show based on the video game The Last of Us in which, as a result of warming temperatures caused by climate change, a fungus takes over the world and turns humans into parasite-controlled zombies.
“In a fantastical way, the logical links are there, but it’s not likely to happen in real life,” says Will. But while scientists aren’t worried about fungi evolving to turn people into zombies, rising temperatures do pose a real risk of making fungal infections worse.
How does the parasite infect ants?
Creator of The Last of Us Neil Druckmann was reportedly inspired by a nature video showing the fungus, Ophiocordyceps unilateralis, infecting a bullet ant. Cordyceps are a broad category of insect parasites, and a popular health supplement. But only ophiocordyceps control their host’s body.
About 35 of these ophiocordyceps fungi are known to turn insects into zombies, but as many as 600 may exist, says João Araújo, an expert on parasitic fungi at the New York Botanical Garden.
The first signs of infection are erratic and abnormal behavior. Scientists think the parasite takes physical control of its host by growing fungal cells around the brain that hijack an insect’s nervous system to control its muscles. It’s unclear exactly how it does this, whether by releasing a chemical or altering a bug’s DNA, says Will.
It’s a process the fungus has been refining within its specific host since before human history.
“Our hypothesis is that they have been coevolving for about 45 million years,” says Araújo.
Related video: ‘The Last Of Us’ Zombie Virus Is Very Real (unbranded - Newsworthy) Duration 1:09 View on Watch
Are we sure it can’t infect humans?
For the fungus to move to any warm-blooded animal would require some serious evolutionary work.
“If the fungus really wanted to infect mammals it would require millions of years of genetic changes,” Araújo.
Each zombie-creating fungus species evolved to match a specific insect, so unique strains have little effect on an organism except for the one they evolved to infect. For example, a cordyceps that evolved to infect an ant in Thailand can’t infect a different ant species in Florida.
“If a jump from an ant species is hard, to jump to humans—that’s definitely sci-fi,” says Will. “But this idea that temperature plays a role in fungal infections is certainly reasonable.”
A threat from rising temperatures?
Even without a looming threat from parasitic fungi, there are plenty of other fungi to fear.
There are millions of fungal species estimated to exist in the world, and a few hundred are known to be dangerous to humans. One thing that’s protected us from serious fungal infections are our own warm bodies. At around 98°F, human bodies are too hot for most fungal species to spread an infection—they prefer a range of 77°F to 86°F.
“One of the reasons why we have skin fungi is they can get between folds of skin. Those are sort of wet, dark places fungi can proliferate that are cooler than body temperature,” says Shmuel Shoham, an infectious diseases expert at Johns Hopkins University School of Medicine.
“As the Earth warms up, there is concern that the change between environment temperature and body temperature won't be as dramatic,” he says. Hypothetically, that would make it easier for fungi that have evolved to withstand hotter outdoor temperatures to also be able to survive inside the human body.
There is one fungal species capable of infecting people that scientists think may have resulted from warming temperatures, called Candida auris.
It wasn’t even known to science until 2007, but in 2011 and 2012, it was suddenly found on three different continents.
“It came out of nowhere,” says Arturo Casadevall, an infectious disease expert at Johns Hopkins Bloomberg School of Public Health. “The idea is that this fungus was out there, and over the years it adapted to higher temperatures until it could break through.”
When they enter the bloodstream, fungi present symptoms similar to a bacterial infection, Shoham notes. For people with healthy immune systems, fighting them off is typically not an issue. But many are not so lucky: The Centers for Disease Control estimates that 30 to 60 percent of patients infected with the fungus have died, although the possibility they had underlying health conditions makes it difficult to determine how pivotal a role Candida auris played.
But when asked if a fungal outbreak akin to COVID-19 was possible, Casadevall says it’s not out of the question.
Considering that possibility, he posits, “Am I worried about an unknown disease emerging and infecting the immunocompetent? Sure.”
Even without a looming threat from parasitic fungi, there are plenty of other fungi to fear.
There are millions of fungal species estimated to exist in the world, and a few hundred are known to be dangerous to humans. One thing that’s protected us from serious fungal infections are our own warm bodies. At around 98°F, human bodies are too hot for most fungal species to spread an infection—they prefer a range of 77°F to 86°F.
“One of the reasons why we have skin fungi is they can get between folds of skin. Those are sort of wet, dark places fungi can proliferate that are cooler than body temperature,” says Shmuel Shoham, an infectious diseases expert at Johns Hopkins University School of Medicine.
“As the Earth warms up, there is concern that the change between environment temperature and body temperature won't be as dramatic,” he says. Hypothetically, that would make it easier for fungi that have evolved to withstand hotter outdoor temperatures to also be able to survive inside the human body.
There is one fungal species capable of infecting people that scientists think may have resulted from warming temperatures, called Candida auris.
It wasn’t even known to science until 2007, but in 2011 and 2012, it was suddenly found on three different continents.
“It came out of nowhere,” says Arturo Casadevall, an infectious disease expert at Johns Hopkins Bloomberg School of Public Health. “The idea is that this fungus was out there, and over the years it adapted to higher temperatures until it could break through.”
When they enter the bloodstream, fungi present symptoms similar to a bacterial infection, Shoham notes. For people with healthy immune systems, fighting them off is typically not an issue. But many are not so lucky: The Centers for Disease Control estimates that 30 to 60 percent of patients infected with the fungus have died, although the possibility they had underlying health conditions makes it difficult to determine how pivotal a role Candida auris played.
But when asked if a fungal outbreak akin to COVID-19 was possible, Casadevall says it’s not out of the question.
Considering that possibility, he posits, “Am I worried about an unknown disease emerging and infecting the immunocompetent? Sure.”
What scientists say about the real-life zombie fungi that inspired 'The Last of Us'
Story by Kate Golembiewski • CNN
The zombies are identifiable by the fungi bursting from their bodies: a thicket of spiky tendrils, a miniature garden of mushroom-like fruiting bodies. These fungal parasites act as puppeteers, commanding and positioning the zombies to infect entire communities.
It’s the premise of “The Last of Us,” a video game series and now a show on HBO, which shares parent company Warner Bros. Discovery with CNN, but it’s also a scene that plays out in real life every day around the world.
Are zombie fungi real?
The creators of “The Last of Us” have said they were inspired by a sequence in BBC’s “Planet Earth” documentary series depicting an ant infected with a fungus that hijacks its brain, forcing it to climb a tree and dangle above the forest floor. There, the fungus digests the ant’s body from the inside out and unleashes a shower of spores to create more zombies.
When “Planet Earth” came out in 2006, the zombie ant fungus was believed to be part of the group Cordyceps, but genetic studies have since placed it in another insect-parasitizing fungus group, Ophiocordyceps.
What scientists say about the real-life zombie fungi that inspired 'The Last of Us'© Provided by CNNFungi of the group Ophiocordyceps, including Ophiocordyceps odonatae, the one that infected the dragonfly pictured here, each generally prey upon a particular insect. - Biosphoto/Alamy Stock Photo
There are well over 100 known Ophiocordyceps species that infect a wide variety of insects, including butterflies, moths and beetles, and at least 35 that perform “mind control” on their hosts.
“We only know 35, but our estimates range to more than 600 species, waiting to be described,” said João Araújo, an assistant curator of mycology at the Institute of Systematic Botany of the New York Botanical Garden.
Can fungi infect and control humans?
While zombie fungi are real and numerous, Araújo and others aren’t worried about Ophiocordyceps infecting people.
“They’re super species-specific,” said Charissa de Bekker, an assistant professor in the biology department at Utrecht University in the Netherlands.
Each of the known Ophiocordyceps species preys upon a particular insect, and that specificity is a double-edged sword. “They have very refined machinery to interact with their hosts and do these really interesting things like changing behavior, but they can’t even jump from one species to the next,” let alone to an organism as distantly related as a human, de Bekker explained.
Humans’ immunity to Ophiocordyceps is evident in how many interactions with the fungi have so far proved harmless. People in parts of Asia use one type (Ophiocordyceps sinensis) in traditional medicines, and scientists who study the fungi haven’t been infected.
“I inhale Ophiocordyceps spores all the time because I work with them closely,” said Araújo, who remains un-zombified.
While we may be safe from Ophiocordyceps, David Hughes, one of the scientists who consulted on the video game, said there is a lesson to be learned from the “The Last of Us,” which is essentially a story about existential threats to humanity.
“The biggest threat globally is climate change,” said Hughes, who has shifted his research focus away from zombie ants and is now Dorothy Foehr Huck and J. Lloyd Huck Chair in Global Food Security at Pennsylvania State University.
Fungal disease and climate change
“The Last of Us” raises the point that climate change could spur on fungal adaptations to hotter habitats. That’s true of the infectious fungus Candida auris, which was discovered in 2009 and has since been found in more than 30 countries.
“In a warming world, fungi also have to adapt to a warmer climate,” de Bekker said. “And you can imagine then, if their optimal growth temperatures therefore become higher and closer to our body temperatures, it might be more likely that in the future, we have more fungal infections in humans than we see right now.”
A widespread fungal pandemic is unlikely, based on how fungal infections tend to spread in humans, according to Dimitrios Kontoyiannis, deputy head in the division of internal medicine at the University of Texas MD Anderson Cancer Center and the leader of its Medical Mycology Research Center.
Meet the real-life zombie fungi that inspired 'The Last of Us'© Provided by CNNThe creators of "The Last of Us" have said they were originally inspired by a BBC documentary depicting a fungus that hijacks the brains of ants. - Oliver Thompson-Holmes/Alamy Stock Photo
However, Kontoyiannis noted that fungal diseases are harder to treat than bacterial infections because fungi, like humans, are made of eukaryotic cells and share the same basic cell structures. This makes it very difficult to find a treatment “that targets the fungus and not the humans,” he said.
A warmer future with more fungal infections would especially endanger people with weakened immune systems, Kontoyiannis added.
Hughes said he hopes people who engage with “The Last of Us” see the parallels to the real-life challenges facing our world, including climate change and new health threats that will accompany it. “The whole thing is a real-time study in what we pay attention to and what we act on,” he said.
Story by Kate Golembiewski • CNN
The zombies are identifiable by the fungi bursting from their bodies: a thicket of spiky tendrils, a miniature garden of mushroom-like fruiting bodies. These fungal parasites act as puppeteers, commanding and positioning the zombies to infect entire communities.
It’s the premise of “The Last of Us,” a video game series and now a show on HBO, which shares parent company Warner Bros. Discovery with CNN, but it’s also a scene that plays out in real life every day around the world.
Are zombie fungi real?
The creators of “The Last of Us” have said they were inspired by a sequence in BBC’s “Planet Earth” documentary series depicting an ant infected with a fungus that hijacks its brain, forcing it to climb a tree and dangle above the forest floor. There, the fungus digests the ant’s body from the inside out and unleashes a shower of spores to create more zombies.
When “Planet Earth” came out in 2006, the zombie ant fungus was believed to be part of the group Cordyceps, but genetic studies have since placed it in another insect-parasitizing fungus group, Ophiocordyceps.
What scientists say about the real-life zombie fungi that inspired 'The Last of Us'© Provided by CNNFungi of the group Ophiocordyceps, including Ophiocordyceps odonatae, the one that infected the dragonfly pictured here, each generally prey upon a particular insect. - Biosphoto/Alamy Stock Photo
There are well over 100 known Ophiocordyceps species that infect a wide variety of insects, including butterflies, moths and beetles, and at least 35 that perform “mind control” on their hosts.
“We only know 35, but our estimates range to more than 600 species, waiting to be described,” said João Araújo, an assistant curator of mycology at the Institute of Systematic Botany of the New York Botanical Garden.
Can fungi infect and control humans?
While zombie fungi are real and numerous, Araújo and others aren’t worried about Ophiocordyceps infecting people.
“They’re super species-specific,” said Charissa de Bekker, an assistant professor in the biology department at Utrecht University in the Netherlands.
Each of the known Ophiocordyceps species preys upon a particular insect, and that specificity is a double-edged sword. “They have very refined machinery to interact with their hosts and do these really interesting things like changing behavior, but they can’t even jump from one species to the next,” let alone to an organism as distantly related as a human, de Bekker explained.
Humans’ immunity to Ophiocordyceps is evident in how many interactions with the fungi have so far proved harmless. People in parts of Asia use one type (Ophiocordyceps sinensis) in traditional medicines, and scientists who study the fungi haven’t been infected.
“I inhale Ophiocordyceps spores all the time because I work with them closely,” said Araújo, who remains un-zombified.
While we may be safe from Ophiocordyceps, David Hughes, one of the scientists who consulted on the video game, said there is a lesson to be learned from the “The Last of Us,” which is essentially a story about existential threats to humanity.
“The biggest threat globally is climate change,” said Hughes, who has shifted his research focus away from zombie ants and is now Dorothy Foehr Huck and J. Lloyd Huck Chair in Global Food Security at Pennsylvania State University.
Fungal disease and climate change
“The Last of Us” raises the point that climate change could spur on fungal adaptations to hotter habitats. That’s true of the infectious fungus Candida auris, which was discovered in 2009 and has since been found in more than 30 countries.
“In a warming world, fungi also have to adapt to a warmer climate,” de Bekker said. “And you can imagine then, if their optimal growth temperatures therefore become higher and closer to our body temperatures, it might be more likely that in the future, we have more fungal infections in humans than we see right now.”
A widespread fungal pandemic is unlikely, based on how fungal infections tend to spread in humans, according to Dimitrios Kontoyiannis, deputy head in the division of internal medicine at the University of Texas MD Anderson Cancer Center and the leader of its Medical Mycology Research Center.
Meet the real-life zombie fungi that inspired 'The Last of Us'© Provided by CNNThe creators of "The Last of Us" have said they were originally inspired by a BBC documentary depicting a fungus that hijacks the brains of ants. - Oliver Thompson-Holmes/Alamy Stock Photo
However, Kontoyiannis noted that fungal diseases are harder to treat than bacterial infections because fungi, like humans, are made of eukaryotic cells and share the same basic cell structures. This makes it very difficult to find a treatment “that targets the fungus and not the humans,” he said.
A warmer future with more fungal infections would especially endanger people with weakened immune systems, Kontoyiannis added.
Hughes said he hopes people who engage with “The Last of Us” see the parallels to the real-life challenges facing our world, including climate change and new health threats that will accompany it. “The whole thing is a real-time study in what we pay attention to and what we act on,” he said.
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