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STEM Journeys

Could We Become The Last of Us?

Country of Origin: United States of America

A pandemic caused by fungal spores is the exact premise of a popular gaming franchise called “The Last of Us”. Is there any justification for humans to fear a fungal-based diseased world?

We can start by defining the characteristics that plummet the fictional world into crisis. Without too many spoilers, the game uses Cordyceps fungus which has mutated. The resulting spores are able to infect humans by targeting their neural pathways, and also continue infecting new humans by transfer of body fluids. The driving goal of the world is to find a cure. Obviously, there are some shared characteristics to the world that we have lived through, which aids the game in creating an immersive scenario. Quick outbreaks lead to overwhelmed healthcare systems, which causes panic and worse, and the resulting disruption to daily life is felt on a global scale. The main difference is the level of violence a fungally-infected person is compelled to inflict on others.

So, can any fungus on earth create aggression? There’s no scientific evidence of such a fungus in the real world. Aside from being poisonous when ingested, there are some species of fungi that can “infect” a human which causes headaches and fever and fatigue. There’s even a species of Cordyceps fungi that is capable of infecting insects to alter their behavior to prioritize growth of the Cordyceps instead of the insect. But these insects and arthropods are small compared to humans. It’s virtually impossible that Cordyceps would be able to grow to an overwhelming concentration in humans. This is why the game stresses that the Cordyceps are a mutated species.

(Photo by Ali Bakhtiari on Unsplash)

As a scientist, I wonder if we have already identified any genes within Cordyceps that would increase the strength or hasten the growth. So I looked and the answer was “no”. While Cordyceps is a well studied species, we have not discovered any specific gene that makes it a stronger parasite. So far, it seems like the reason Cordyceps is even able to manipulate behavior in its host is because of the fungal metabolites produced.

The problem is that ‘metabolites’ is a rather large umbrella term that can include complex neurotransmitters or simple sugars. This means it is possible that small molecules and neurotransmitters target the host’s nervous system, or that the immune system of the host is challenged leading to a significant change in behavior.

Again, the size of an ant compared to a human means that a few Cordyceps cells are able to manifest as a significant disease. As humans, our immune system would likely recognize the invasive Cordyceps spores before they could replicate through the many many cycles needed to generate a substantial infection.

It seems rude to critique the practicality of infection without offering my own. I would have proposed using Chronic Wasting Disease (CWD) which is a serious transmissible spongiform encephalopathy that is killing deer, elk, and moose in the North American continent. I hope that you never witness such an infection, as it would mean a growing harm to nearby cervid populations, but deer and their genetic relatives experience weight loss, lethargy, and other symptoms that eventually lead to death. The slow development of symptoms is part of the reason for the widespread infections, as deer appearing healthy are able to engage in behaviors that lead to transmission before the other members of the herd realize they are at risk. Little by little, their bodies become infected with high amounts of misfolded proteins, more specifically known as prions, and these levels of prions are able to interfere with normal behaviors controlled by the nervous system. The deer pace, and droop their heads, and their brain becomes increasingly more inflamed. Along with the deer, wildlife management agencies are heartbroken to manage infections in these populations. There is not yet a cure, so the best course of action is to isolate suspected infected deer from the main herd and take action as necessary to spare the deer continued pain. 

Currently, there is no reported threat to humans for CWD. Similarly, a zombie apocalypse as depicted in popular culture is not a scientifically feasible possibility in the real world. The idea of a zombie outbreak, characterized by the reanimation of the dead and their subsequent attack on the living, is purely fictional and has no basis in science.

However, there are some real-world scenarios that have been used as inspiration for the zombie genre. For example, some diseases like rabies can cause aggressive and erratic behavior in infected individuals, which could resemble the portrayal of zombies in movies and TV shows. Additionally, pandemics and other widespread outbreaks of infectious diseases could cause widespread panic and social disruption, which could mimic some elements of a zombie apocalypse.

It’s important to note that these real-world scenarios are still far from the classic depiction of a zombie apocalypse and should not be taken as evidence that such an event is likely to occur. They are simply points of inspiration for creative works, and should not be a source of fear or concern for the general public.

While the topics of dystopian-era diseases are not kind to the heart, we are not powerless. The genre of survival games are parallel to the world in which we all live. Similarly to how Sci-Fi is a feedback loop for innovation that can inspire accessibility, I believe that survival games breed empathy and awareness to horrifying diseases in our world. With every mind that begins to love the universes in fictional games, there becomes a new innovator in the world of medical interventions. Now it is your turn, to share what diseases you have heard of that relate in some small way. One thing that fictional or non-fictional worlds need to survive is global collaboration to keep the balance of life safe.    

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