The Science of Zombies: “The Last of Us” and Beyond

By Elizabeth Fusco, edited by Michael Liesen

Infection and pandemics have never been more relevant globally, and zombies have long been used to express this fascination in pop culture. Given the interest in zombies in American popular culture, Elizabeth Fusco connects zombies to a scientific context with this piece. -ML

From horror movies to children’s toys, zombies are a staple in American pop culture. The word zombie arises from sugar cane plantations in Haiti, where the word zonbi describes one’s soul. The slaves on these plantations believed a sorcerer could cast a spell to turn a person into a zombie.  One of the substances used in these spells is tetrodotoxin, a deadly neurotoxin most famously found in pufferfish. Tetrodotoxin induces zombie-like symptoms, such as difficulty walking and mental impairment. Clarivius Narcisse is a famous case of zombie-fication by tetrodotoxin poisoning. He was admitted to the hospital and pronounced dead, only for his sister to identify him at a village market 18 years later! Once reunited with his family, he recounted what it was like to enter a zombie-like state.

From Haiti to Hollywood

Tales of zombies made their ways from Haiti to Hollywood, and zombie films began to arise in the mid-1900s, with the most notable early zombie film being Night of the Living Dead. In this movie, radiation from a space explosion emanated toward Earth, reanimating the dead and giving them an appetite for human brains. In addition, zombie viruses are also a commonly used mode of infection, and these viruses cause zombie outbreaks in many popular shows and movies, such as The Walking Dead and World War Z. More recently, the video game and television show The Last of Us shines a new light on the zombie trope, exploring a zombie pandemic induced by an infectious fungus.

After the onset of the COVID-19 pandemic, many wonder what the next global health emergency will be. While The Last of Us video game was developed before the pandemic, the television show was written during it, and the writers did an amazing job using elements of the COVID-19 pandemic to make The Last of Us universe feel realistic and applicable. For example, one of the opening scenes of The Last of Us focuses on two scientists on a talk show in the 1960s. They are discussing pandemics and what would most likely cause the next pandemic.

The first scientist gives an expected answer, to fear viruses. The second offers a more unconventional idea and states we should be fearful of a fungi-induced pandemic. While the audience laughs, he warns that we have no effective fungicides and that fungus is more likely to mutate as the Earth warms, allowing it to infect warm-blooded humans, leaving us as “billions of puppets with poisoned minds.” In The Last of Us universe, his fears come true, and 40 years later, fungi mutate to infect humans. The inspiration for this pandemic comes from a real-life fungal species: cordyceps.

Cordyceps in Context

Image credit

Cordyceps infected ant on a stick. by Bernard DUPONT from FRANCE, CC BY 2.0

Overall, the show makes the cordyceps infection in humans seem realistic, and you can tell that they consulted with scientists who study fungi when creating it. Cordyceps are also known as the ‘zombie ant fungus’ due to their ability to infect ants and control their minds. After infection, the fungus grows within the ant and eventually controls the ant’s brain. The control method of the cordyceps in The Last of Us mimics how cordyceps control ants, where once infected, the cordyceps command the victim to infect as many other people as possible to spread the fungus. In The Last of Us, the cordyceps also take root and spread throughout the infected being’s body. The show even highlights this in a scene where Ellie cuts the flesh of a dead infected, and cordyceps tendrils come spilling out.

In The Last of Us universe, cordyceps infection begins when an infected individual bites a victim. Then, depending on how far the bite is from the brain, it takes variable amounts of time for the fungus to take control. While bites do not cause fungal infections, this route of infection is how the disease rabies is spread, which may be the inspiration for this aspect of infection in The Last of Us. In our universe, cordyceps spread through airborne spores rather than a bite. In the video game form of The Last of Us, the characters wear gas masks to protect themselves from infectious, airborne spores. Still, this concept was scrapped in the television show so that audiences could better see the actors’ faces.

How Real is The Last of Us Really?

Nevertheless, a few aspects of The Last of Us do not mirror reality. First, there is still no known case of cordyceps infecting humans. Surprisingly, many people actually take cordyceps as a supplement, and research has shown that cordyceps can strengthen the immune system and may even have some cancer-fighting properties. In the show, Tess states, “You step on a patch of cordyceps in one place, you can wake a dozen infected somewhere else,” indicating that the infected are all connected through a root-like system. However, this is not observed in cordyceps-infected ants. However, trees in a forest can communicate with one another through underground fungal networks connected to their root systems, which could be the inspiration behind the connection of the infected in The Last of Us.

The Last of Us gives us a unique take on the zombie apocalypse. Although the show is fictional, many aspects are based on scientific truth, and it has exposed its viewers to the beautiful world of fungi. Hopefully, this show has also piqued the public’s interest in learning more about the world and the amazing microbes that inhabit it.