Video game-turned-HBO series “The Last of Us,” of course, is science fiction. Yet the idea is loosely based on a real fungus, cordyceps, that infects and manipulates the behavior of a wide range of insects, including ants. These cordyceps infect an ant, grow inside its body and then force the ant to climb to a high point on a plant or tree, where it can release fungal spores to infect and take over the greatest number of ants possible.
This behavior manipulation is what has earned the real-life fungi the nickname “zombie-ant fungi,” as the ant behaves as if it is controlled by a “zombie” force. It’s a fascinating example of how fungi can manipulate other organisms for their own benefit.
A relative of the zombie-ant fungus, Cordyceps sinensis, known as Dongchongxiacao (winter-worm summer-grass) in Chinese, is one of the most popular traditional Chinese medicines, recommended for everything from anti-aging to cancer suppression. Cordyceps, like so many other fungi, have properties both beneficial and dangerous—if you are an ant, that is.
The setup for “The Last of Us” series is a one-minute scene, purportedly a 1968 talk show interview with experts on fungi. It felt all too real to me.
“A fungus cannot survive if its host’s internal temperature is over 94 degrees [Fahrenheit],” one actor playing a scientist tells the others. “And currently there are no reasons for fungi to evolve to be able to withstand higher temperatures.”
Then he proposes what might have seemed a highly unlikely scenario in the 1960s: “But what if that were to change? What if, for instance, the world were to get slightly warmer?”
He goes on to say, “Well, now, if there is reason to evolve, one gene mutates and then . . . any one of them could become capable of burrowing into our brains and taking control not of millions of us but billions of us. 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. It’s not even possible to make them.”
“So, if that happens?” asks the wide-eyed host. “We lose,” comes the somber reply.
People keep asking me if a fungal crisis like the one in “The Last of Us” could really happen. I’ve told them, in science, you never say no. Sure, it’s far-fetched that a fungus will turn people into zombies, even though it actually does that to ants.
But what are scientists who are studying cordyceps learning about how the fungus is able to replace the nervous system of ants? Maybe, someday, this basic science could help us understand how a fungus can cause paralysis, and maybe that understanding could lead to technology that could help someone walk again. That is also not out of the realm of scientific possibility.
While the plot of the television show firmly resides in the world of make-believe, there’s no question in my mind that we’re likely to see dangerous new fungal pathogens emerge. We already have. With climate change continuing its march, we will undoubtedly see more.
I often think about how when I went to medical school in the late 1970s and early 1980s, we learned that retroviruses (such as HIV, which we hadn’t yet identified), known to cause disease in other animals, were harmless to humans. Scientists had studied these retroviruses, which caused experimental tumors in mice in the lab, mainly because they were trying to determine whether they could learn something useful in the war on cancer. Well, in my second year of medical school a retrovirus was associated with a rare human disease known as tropical spastic paraparesis, and a few years later we learned that HIV was the cause of AIDS.
In those days, we were also taught that coronaviruses would do nothing more than give people the sniffles. Only when SARS came along in 2003, an epidemic that sickened more than 8,000 people and killed 774, mostly in China and Hong Kong, did we understand that coronaviruses could be pandemic threats. COVID-19 confirmed it on a massive worldwide scale.
Just as retroviruses and coronaviruses once were, the fungal kingdom remains an afterthought. Like the generals who prepare for the last war, we focus on known threats. That’s why we’re so often surprised and unprepared when something new does emerge. A fungal pandemic remains unlikely today because fungi, generally speaking, don’t spread efficiently from human to human. But it may not always stay this way. Quietly, fungi are being revealed more as a potential enemy building strength. We don’t necessarily know which fungi will strike, or where, or in what numbers.
What we do know is that we need to stop ignoring fungi and the threats they pose, treating them as less dangerous than bacteria or viruses. They should no longer be second-class citizens in the world of pathogens. We need new and better ways to protect ourselves and the crops on which we rely.
At the same time, let’s continue to focus on the incredible natural abilities of fungi to potentially protect us from radiation, from depression, from single-use plastics, from so many other big problems that need solving. Science can win if we put our resources — financial, human, and more — behind it.
This piece was excerpted from “What if Fungi Win?” by Dr. Arturo Casadevall; Copyright 2024 Johns Hopkins University Press
