WORDS BY YESSENIA FUNES
HBO’s latest drama The Last of Us portrays a future plagued by fungi that turn humans into zombies. The Frontlineexplores the actual fungi that threaten public health.
Zombie enthusiasts have been glued to their televisions for the past two Sundays to watch HBO’s latest series The Last of Us. The show, an adaptation of the bestselling namesake video game, takes place in an apocalyptic world where climate change has fueled a global fungal infection that has turned most humans into flesh-eating zombies. The survivors are left navigating a highly militarized society where monsters and war run rampant.
Nowadays, we don’t have to look far to imagine a deadly infectious disease. Look at COVID-19, the virus that brought the world to a standstill in 2020 and continues to kill hundreds (if not thousands) a day. The total death toll looms over 6 million, yet here we are, carrying on with business as usual as if lives aren’t being ravaged every day by a virus our governments could’ve stabilized years ago.
Could climate change facilitate the creation of something worse: a parasitic fungal disease that turns us into zombies like The Last of Us? The seven scientists interviewed for this story all said no, that’s highly unlikely. The climate crisis is, however, already increasing the threat humans face from other sorts of fungal infections, the researchers clarified. What makes this threat all the more dangerous is that it isn’t operating alone.
What’s coming is a polycrisis—a monster worse than the fictitious zombies we obsess over because, this time, it’s real. The wave of crises won’t stop just because we’re already in one. In our world of fossil fuel pollution and corporate greed, crisis breeds more crises. With respect to public health, world leaders need to prepare for future outbreaks that will be embedded in this web of disasters, especially if they are going to protect society’s most vulnerable.
In The Last of Us, a strange fungus appears, driving humans to cannibalistic and violent behaviors. This is how it eventually spreads: the infected attacking the living.
In the video game, the fungus originates in South America where it infects crops before spreading elsewhere via spores, the microscopic particles fungus release to reproduce. The latest episode on Sunday seemed to confirm a popular theory on how the fungus first spreads in the game: that people are exposed through flour originating in Jakarta, Indonesia, before they infect one another.
Viewers get a glimpse of what the initial infection looks like in the show’s premiere where an old lady (the first zombie we see) has writhing branches protruding from her mouth, the mycelium threads from the fungus that has taken over her body. As the most recent episode depicted, these branches can grow larger and more elaborate in later zombie stages, eventually exploding from a person’s face. These zombies are called clickers, and the stages of infection only grow more gruesome from there.
Though the idea of human zombies is entirely science fiction, The Last of Us is inspired by a real-world phenomenon: zombie ants. In the game, the disease is called Cordyceps Brain Infection, or CBI. Ophiocordyceps (more popularly known as Cordyceps) is a genus of fungi that includes many species, many of which are parasitic. Biologists have described about 300 species in the genus, 35 of which can manipulate host behavior, said João Araujo, a curator in mycology at the New York Botanical Garden. They estimate that some 600 species may actually have the power to function as zombie fungi.
Ophiocordyceps unilateralis is a tropical species that targets ants. After an ant has contact with a spore, the fungus begins to move through its insides and eventually takes over its brain. At that point, the fungus is in control, so the zombified ant travels to higher treetops in the forest canopy before exploding with spores, sprinkling the fungus below.
“Eventually, a passing-by ant will get in contact with these spores and become infected, restarting the life cycle,” Araujo said in an email.
This can happen to other bugs, too—like fruit flies, an area studied by Dr. Carolyn Elya, a postdoctoral fellow at Harvard University. It dies similarly to the ants with the fungus, Entomophthora muscae, growing out of the fly’s exoskeleton, releasing spores into the environment.
The video game doesn’t mention climate change, but HBO’s adaptation of The Last of Usstarts with a televised interview in 1968 where a scientist declares, “There are some fungi who seek not to kill, but to control,” speaking of the zombie ant. When the scientist sitting next to him challenges whether this can happen to humans whose bodies are too warm for these species of fungi, he responds: “Currently, there are no reasons for fungi to evolve to be able to withstand higher temperatures, but what if that were to change? What if, for instance, the world were to get slightly warmer?”
Well, we live in a warmer world now. Does that mean humans are next?
“This is pure fantasy (but so cool, right?),” Araujo said. “The fungus would require millions of years of genetic changes and adaptations in order to infect such a completely different group of organisms from what they are currently adapted to infect.”
Still, scientists still have a lot to uncover about these specific sorts of fungi, Elya at Harvard said in an email: “There is a ton that we don’t know about how these fungi alter host behavior. What’s great about shows like The Last of Us is that, in addition to entertaining folks, it can drive more awareness about the real natural phenomenon that inspired this story.”
“Mycology is one of the most neglected disciplines in biology and harbors one of the largest reservoirs for new discoveries.”
JOÃO ARAUJO
NEW YORK BOTANICAL GARDEN
Climate Action Australia 