The Last Of Us: Inspiration Behind the Infected

The Last Of Us, released in 2013 by Naughty Dog, was met with critical and fan acclaim, and many believe that it is on its way to become a classic. The game is applauded for its simple yet effective narrative direction, as well as gameplay mechanics. The game follows a tried and true formula: surviving an undead apocalypse. Zombies have dominated the video game industry for years, from Resident Evil to Dead Island,and these creatures have been imagined in a variety of forms and with different names. However, a common consensus is that they represent our inner animalistic nature that has come to life.The usual trope is a virus outbreak that leads to the undead. The Last Of Us breaks the zombie infection mold by presenting a different take on zombies: a fungal infection. The Infected in The Last Of Us behave like the zombies we have come to know, but their appearance and infection inspiration are unique. The infection that devastates the world in The Last Of Us is the Cordyceps Brain Infection, and it is modelled after the real life Cordyceps fungus. The inspiration behind the Infected came to the directors, Bruce Straley and Neil Druckman, after watching a BBC Planet Earth clip.

“Nature is way scarier than anything we could ever imagine.”

The clip from BBC’s Planet Earth showcases the Cordyceps fungus and its infection of an ant. The ant then proceeds to latch onto a tree stem and the fruiting body of the Cordyceps begins to grow out of the ant’s head. The complete growth may take up to three weeks, but once complete the spores will be released, and any ants in the vicinity are likely to become infected and follow the same fate. If an infected ant is discovered, the other ants will dump the infected away from the colony in order to protect the rest of the colony. In an interview with Game Informer ¹, the lightbulb of inspiration didn’t turn on right away for Straley and Druckman, but it came at the end when the the narrator, Sir David Attenborough, stated that the more numerous the species, the more likely it was to become infected. “What if this thing jumped to humans?” is the question that Druckman and Straley attempted to answer when they created the Infected.

CORDYCEPS

There are thousands of different species of Cordyceps. Cordyceps are a genus of ascomycete fungi, commonly known as the ‘sac fungi’, and are mostly parasitic on insects and arthropods. They reproduce by releasing ascospores (spores that are not capable of movement on their own), usually held in an ascocarp (the fruiting body that grew out of the ant’s head). Cordyceps are mostly used as medicinal mushrooms. The species most often used for pharmaceutical purposes are Cordyceps militaris and Cordyceps sinensis, which is considered a caterpillar fungi. Medicinal uses of Cordyceps can be dated back hundreds of years according to Chinese and Tibetan medical books. They predominately grow in humid climates. The Cordyceps species shown in the Planet Earth documentary, Ophiocordyceps unilateralis, is a unique species because it can alter the mind of the infected insect. Most Cordyceps do not have that ability and function like regular fungi. The Infected in The Last Of Us, although no specific species was mentioned in the game, appears to be inspired by Ophiocordyceps unilateralis, as well as Cordyceps ignota. ^{2 3}

Ophiocordyceps unilateralis

This species of Cordyceps is the major inspiration behind the Infected from The Last Of Us. It is also referred to as the ‘zombie fungus’. The target of O. unilateralis are the carpenter ants that commonly reside in forests. Once the fungus infects the insect it will release chemicals that attack the nervous system of the ant. Once the nervous system is attacked the ant will become a puppet to the fungus. The ant will then be forced to attach itself, via the ‘death grip’, onto a branch of vegetation. This is where the ant will stay until it dies. At this point the ascocarp will grow out of the ant’s head and release spores with the intent to infect other ants. The fungus relies on reproduction through the ants in order to survive. Studies by Charissa de Bekker ⁴, a molecular biologist at Pennsylvania State University, indicate that the fungus creates different chemicals for different ant species. This suggests that the O. unilaterallis may ‘know’ the brain of its target and can adapt accordingly. Further research is going to look into how this phenomena works, as well as which chemicals are secreted. De Bekker’s studies suggest that guanidinobutyric acid (GBA) and sphingosine are involved in the brain hijacking process. Interestingly enough, these chemicals also appear to play a role in human neurological disorders.

Cordyceps ignota

The main target for this species of Cordyceps are tarantulas. The Cordyceps ignota species has elaborate ascocarp growth that produces multiple fruiting bodies. Like Ophiocordyceps unilateralis, Cordyceps ignota will slowly kill its prey and then release spores in order to complete the life cycle. Cordyceps ignota does not zombify the tarantula, it merely kills it. Tarantulas who are infected by Cordyceps ignota create a strikingly beautiful, yet terrifying image.

The Infected

In The Last Of Us the Cordyceps Brain Infection was caused by infected crops from South America. This can be found at the beginning of the game by reading a newspaper in Joel’s house. All the information gathered in game about the infected comes from files found throughout the game. According to a pamphlet found in game, the only way to become infected is by bodily contact with an Infected or by inhaling the spores released by Infected corpses. The same pamphlet also mentions that there is no known cure for the Cordyceps Brain Infection. It also appears that the Center for Disease Control has stopped looking for a cure. However, a militia group, The Fireflies, are still searching for a treatment. Finding a cure has proven difficult because the fungus grows while the host is still alive, effectively slowly ceasing their higher brain function, and within two days the host will enter stage one of the infection.

Stage one of the infection is the weakest stage. The Infected are referred to as Runners. They have poor eyesight; the cordyceps attack the eye area first. However, Runners still have a physical human resemblance and their moans are still human. Their body language is slow, perhaps an indication that they are trying to resist the infection still, but they will attack readily when provoked. Runners, although still human-like, have heightened senses and can more easily detect the player than human AI’s. The Runners are more stylized as a modern interpretation of a zombie as opposed to the Infected caused by the Cordyceps.

Stage two begins shortly after a week from infection and can last up to a year. The Infected in this stage are referred to as Stalkers. During this stage the Infected have the vision and speed of the Runners, but they attack with the fierceness attributed to the stage three infected. Stalkers begin to show proficient fungal growth on the body, most notable around the head. Sometimes this fungal growth appears to be glowing. This glow actually comes from the fungus. Cordyceps are capable of bioluminescence. The fungal growth at this stage will have taken over most of the Infected’s face, leaving only one eye visible. Stalkers are easily recognized by their croaking sounds caused by the fungus advancing in the throat. Stage two is also the stage when the beginnings of echolocation start to take place. Echolocation begins because the Infected are becoming less reliant on the sense of sight since their eyes are practically destroyed entirely by the fungus. Stalkers like to hide and then ambush their victims, exemplifying that the Infected have become more animalistic in nature.

The third stage of the infection takes place about a year after initial infection and the Infected are named Clickers; named aptly for the ‘clicking’ sound it makes when using echolocation. At this stage the Infected has had prolonged exposure to the Cordyceps fungus and have virtually no human resemblance except for their body shape. The Clickers, like the Stalkers, can be seen glowing due to bioluminescence.The fungus has completely taken over the head and the Clicker relies solely on echolocation to find its prey. The echolocation is not as sophisticated as the echolocation used by bats, but aligns more with human echolocation used by those who are blind. Bruce Straley mentioned a blind boy who could ride is bike using only echolocation as inspiration. When a Clicker locates the player it will go berserk and attack until you, or it, is dead.

The fourth and final stage of the infection is the Bloater stage. Not much is known about the Bloater stage because it is rare to encounter a Bloater. It is unknown how long it takes to reach the final stage, but it estimated that it takes at least ten years after the initial infection. A Bloater has a fungal armour surrounding its body, therefore making it hard to pierce and kill. Like Clickers, the Bloaters use echolocation to find its prey, however since the Bloater has a completely deformed face the echolocation is less refined than a Clickers. Bloaters throw Mycotoxin, a common toxin released by various fungi, at the player.

Once an Infected has been killed the fungus will continue to grow, just like real life Cordyceps. It will grow to cover the entire body of the Infected and the fungus will attach the body to any nearby surface. The fungus will then emit spores that will infect anybody in the vicinity. This is why Joel, and other human characters, can be seen wearing face masks throughout the game.

The life cycle of the Infected is quite similar to the life cycle of many Cordyceps fungi. This is especially true regarding the death phase of the fungus. The overall behaviour of the in-game Cordyceps fungus is similar to O. unilaterallis, but the appearance of the Infected more closely resembles Cordyceps ignota.

Could We Become The Infected?

As of right now there is no evidence to suggest there will be a Cordyceps infection that wipes out up to sixty percent of mankind like in The Last Of Us. There is no species of Cordyceps that targets humans, and the fact that many species of Cordyceps are orally taken for medicinal purposes further enhances the fact that Cordyceps are not a real imminent danger for humans. However, that does not mean it couldn’t happen. With any living species there is evolution. In hundreds or thousands of years the Cordyceps fungus could, theoretically, adapt to infect humans. It would take an extensive amount of time since there is no known Cordyceps that infects mammals presently. While it is possible that a Cordyceps infection could, eventually, target humans naturally, it is not thought of as a threat.
The idea of a man made Cordyceps infection is also intriguing. Cordyceps have been studied for medicinal purposes for centuries, but new discoveries involving species like O. unilaterallis have led to more research on the fungi’s freaky infection. It could be possible that future experimentation with the Cordyceps fungus could lead to a man-made bioweapon in the future. Although, this can be said for any fictional infection presented in media. The notion that the Cordyceps fungus could infect humans is one that is distant and, at the moment, is known to be practically non-existent. It is interesting to theorize about though.

Joel and Ellie are the stars of The Last Of Us, but the Infected encountered are stars in their own way. The research behind the Infected is based on something concrete and real, and it leads to a refreshing take on the zombie apocalypse trope. Using a real fungus leads to interest in real science and nature, and that is an accomplishment in its own right.

What do you think? Leave a comment.