The "zombie fungus" in "The Last of Us" really exists! What would happen if humans were infected?

Unknown pathogens suddenly appear, and once infected, humans lose their minds and become "zombies" that bite their own kind crazily - we have seen this horror setting too many times in movies and TV shows. Zombies provide plenty of sensory stimulation, but their settings always seem too far-fetched, making it difficult for people to feel real.

However, the recently popular American TV series "The Last of Us" is completely different.

This series and the original game tell a post-apocalyptic story about a fungal infection that turns humans into "zombies" . The heroine Ellie is the only survivor who does not develop symptoms after being infected, and the hero Joel's mission is to escort her across the United States, through numerous dangers, to deliver hope for the development of vaccines and drugs to medical laboratories.

Many zombie stories are purely fictional, but the inspiration for this story comes from reality and can even be said to be quite scientific. The "zombie" story of fungi controlling the host actually happens every day in nature .

"The Last of Us" tells a story about a "zombie fungus" destroying human civilization | HBO

A true zombie story, with ants as the protagonist

The prototype of the deadly fungus in "The Last of Us" is called Ophiocordyceps unilateralis sensu lato. It is not a single species, but a complex group composed of a series of similar species.

In reality, we can breathe a sigh of relief, because it is not humans who are turned into "zombies" by the fungus, but ants - the fungus controls ants with an accuracy of centimeters. If one ant is infected, it is possible that all the ants within 20 to 30 meters around it will suffer .

Ophiocordyceps infects ants. The long, thin structures emerging from the ant's body are the fruiting bodies of the fungus, which are responsible for spreading spores. | Hughes Lab, Penn State

The process of ants being transformed into "zombies" by fungi mainly occurs in tropical forests. The first infected ants will leave their nests, wander around, and eventually climb onto plants and land on the back of a leaf about 25 cm above the ground - studies have found that this is the most suitable location for fungal growth and spread.

The ant uses its last bit of strength to bite the leaf veins tightly, hanging itself upside down and fixing it in place. Then, the fungus will completely kill it and pass through its body, spreading spores to infect more ants . This spread will cause a chain reaction, forming this ant cemetery.

Although ants infected with the fungus do not attack their own kind like fictional zombies, nor do they suddenly become freaks with explosive power, they are the same as the infected in "The Last of Us": their behavior is completely controlled by the fungus, and they have completely become tools for the spread of the fungus .

Although the setting is based on the Cordyceps sinensis fungus, in order to increase the visual impact, the fungi in "The Last of Us" also mix the appearance of mushrooms and slime molds. | Liane Hentscher/HBO

It’s not uncommon for parasites to influence the behavior of their hosts, but the control that Ophiocordyceps sinensis has achieved over ants is so complex and precise that it’s one of the most amazing horror stories in nature.

How do fungi “brain control” their hosts?

Climb to the right position, then bite the leaf veins - this series of complex actions, how can the fungus control the ants to complete it? There is no clear answer to this question yet, and related research is still ongoing.

The most straightforward hypothesis is that the fungus invades and damages the host brain - but a study published in 2017 suggests that things may not be that simple.

Infected ants often hang themselves upside down from the underside of leaves | David P. Hughes, Maj-Britt Pontoppidan

The researchers cut slices of infected ants and scanned them under an electron microscope, then used a computer to reconstruct the distribution of the fungus in the ants’ bodies. The results showed that fungal cells occupied the entire body of the ants, but there was no sign of fungal invasion in the brain [1].

If fungi don't actually enter the brain, how can they control host behavior?

One possibility is that the fungi secrete special chemicals to remotely "control the brain" - but another, more terrifying possibility is that they may not be controlling the brain at all.

The fungus forms an intricate network in the ant's muscle tissue, and it may be able to bypass the brain and directly issue forced movement commands to the host's muscles . According to this scenario, the infected victim may even be fully conscious, but unable to control his own body, and can only watch himself die and spread death to more of his kind.

If The Last of Us adopted this assumption, it would probably make the story more cruel.

Will the infected know that they have become a "zombie"? | HBO

Will humans be controlled?

In reality, Ophiocordyceps sinensis does not infect humans at all. Even if they do mutate and adapt to new environments in the future, the possibility of these fungi turning people into "zombies" is almost zero .

At the beginning of the first episode of The Last of Us, the scientists in the show mentioned a theory: humans are difficult to be infected by fungi because of their high body temperature, and as the climate warms, fungi will adapt to higher temperatures and thus become able to infect humans. This statement makes sense, but it is not so simple to let the "zombie fungus" change its host.

Mammals are less at risk from fungal infections than insects, and scientists believe this is indeed related to differences in body temperature | strangeplants.org

Compared with insects and amphibians, fungi pose less of a threat to mammals, and this is indeed related to temperature. A study tested the heat resistance of 4,802 different fungal strains and found that most of them could not survive at the body temperature of mammals [2]. In theory, climate warming may screen out more fungi that are adapted to high temperatures, reducing the obstacles to their infection of humans. This is indeed an issue that deserves attention in the future.

However, even if the temperature barrier is removed, it does not mean that Ophiocordyceps can easily control humans. These fungi are very specialized, and each fungus can only control a specific species of ants . It is difficult for them to cross species between ants, let alone humans, whose physiological characteristics are very different from those of insects.

In other words, when it comes to the issue of Cordyceps fungus, we can just sit back and appreciate the fictional story and the cruelty of nature from a bystander's perspective.

At least that's certainly the case now.

References

[1]https://www.pnas.org/doi/10.1073/pnas.1711673114

[2]https://pubmed.ncbi.nlm.nih.gov/19827944/

[3]https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis

[4]https://thelastofus.fandom.com/wiki/The_Last_of_Us_Wiki

[5]https://www.theatlantic.com/science/archive/2017/11/how-the-zombie-fungus-takes-over-ants-bodies-to-control-their-minds/545864/

[6]https://www.vox.com/culture/2023/1/21/23561106/last-of-us-fungus-cordyceps-zombie-infect-humans

Author: Window Knocking Rain

Edit: Small towel

Cover image source: HBO

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