If we’re to believe HBO’s zombie apocalypse series The Last of Us, the end of humankind comes via the tentacles of a creepy-looking, brain-infecting fungus called cordyceps.
As with so many terrifying scenarios, the germ-gone-wild depicted in the hit show has roots in the real world.
Cordyceps fungi are real organisms that are most at home in warm, humid climes. They take over the minds of ants as well as certain spiders, moths, locusts, and other arthropods, but thankfully, not humans.
“The fungus attacks insects that live in the ground or soil,” said Rebeca Rosengaus, an associate professor and behavioral ecologist at Northeastern University. “Ants are one but there are also grasshoppers, spiders, locusts.”
Cordyceps’ official name is Ophiocordyceps unilateralis, and yes, scientists call it the “zombie-ant fungus.” It doesn’t spell the end of humankind, but it certainly does spell a grisly end for the creatures it infects.
Here’s how it works: The ant (or other arthropod) ambles innocently out of its nest, looking for food and blissfully unaware that cordyceps spores are raining down from a nearby tree or stem or branch.
The spores latch onto the ant (or other creature), releasing digestive enzymes to break down the insect’s cuticle (hard outer shell). Threadlike growths, known as mycelia, start growing inward and eventually take over the insect’s brain, which start producing neurotransmitters that affect brain function. The transformation is complete: The ant begins to stumble and convulse, acting in a way that benefits cordyceps.
“The fungus basically hijacks the brain so the ants stop doing what ants do and start doing what the fungus wants it to do, which is climb up the tree trunk,” Rosengaus said. Once they’ve reached the treetops, the ants bite the stem or leaf in what’s known as a death grip.
“That’s the last thing they do before the fungus starts growing from the neck or the head of the ant up,” Rosengaus said.
The ants die within six hours of infection, and then two to three days later, a fungal stalk emerges from the neck. Then, the spores start raining down again and the cycle repeats.
That’s life, at least for arthropods.
“Like many organisms on the planet, it does what it needs to do to replicate and continue reproducing,” said Dr. Scott Roberts, associate medical director of infection prevention at the Yale School of Medicine.
Could this ever happen in humans?
The Last of Us is real life for ants but not for humans — at least not yet, Rosengaus said, although she wouldn’t rule it out way down the line. “The fact that we don’t have a pathogen that has been able to come up with this strategy to hijack our minds does not mean that it’s not a possibility at some point.”
For now, though, this isn’t likely to happen in humans. “One of the reasons for that is that humans are warm-blooded,” Roberts said. “Most fungi and molds do not grow well in high-temperature environments.” Humans, which have a body temperature of 98.6 degrees Fahrenheit, are most definitely inhospitable.
“The creators of the show have taken a very niche moment in nature and fictionalized it,” Roberts added. “It’s a popular, great TV show, but it’s not really a viable or realistic portrayal of what could happen.”
“I don’t think we ought to be worried,” William Schaffner, an infectious diseases expert at Vanderbilt University, said. “A fungus is a much higher order, a much more complicated germ than a virus, so it would be a much more complicated phenomenon for this fungus to jump species.”
Which is not to say that humans can’t be infected by organisms that typically infect other species.
“We do have zoonotic infections,” Roberts said. Mpox is a good example. So is COVID-19, which comes from the SARS-CoV-2 virus. “Often viruses and sometimes even fungi can be in another species and jump to other humans, but it usually needs progressive jumping back and forth [between humans and animals].”
Climate change is also introducing new dangers, including new fungi. One is a type of yeast called Candida auris.
The organism’s adaptation to warmer temperatures is thought to be the reason it now has a better chance of being able to survive in the human body. (This is also the reason The Last of Us writers use to explain why cordyceps can infect people.)
While Candida auris gravitates to your skin, it can cause bloodstream infections and is often spread in hospitals and other healthcare settings.
“If you’re healthy, it will stay on your skin and [even] go away, but if you have lines and catheters and have had surgeries, it can cause infections in wounds,” Roberts said. Those infections can spread not just to the bloodstream but also different organs, like the brain and heart.
“It’s a type of the candida species that has emerged with climate change,” Roberts said. “It is possible that other fungi and mold will evolve to survive and reproduce in warmer climates.”
Candida auris, which was first recognized only about 10 years ago, is already resistant to multiple drugs. It also spreads from person to person, unlike other types of molds or fungi that more often come from the environment, Roberts said.
As with most fungi, if you’re healthy, Candida auris isn’t likely to cause any harm. If you’re immunocompromised or otherwise in frail health, though, they can cause severe infections and that can even be potentially life-threatening.
Separating fact from fiction
There’s another entity hijacking our brains right now: science fiction–esque misinformation masquerading as fact.
As long as you realize The Last of Us and other shows are fiction, there’s no harm done.
“For decades, science fiction writers have taken basic ideas to an extreme. That’s part of the fun,” Schaffner said. “As wonderfully rich and extraordinary as real science is, there are real biological limitations, and this would be one of them. When it comes to real life, listen to public health. We’ll tie you to reality.”
It’s not like we need to look for things to worry about. “If you asked me whether this fungus or SARS-CoV-2 will be the end of us, one hundred times out of one hundred I’ll say SARS,” Roberts said.