No one likes getting sick. Debilitating illnesses drain your energy and cause all kinds of nasty fluids to come out of your body. If allowed to spread, these diseases can decimate an entire population. As bad as that sounds, fiction is arguably worse.
Writers have fashioned countless crazy plagues across the storytelling realm. Their insane symptoms are obviously great for shock value, but what’s scarier is how plausible these sicknesses sound. When explaining the viruses, creators often use real illnesses as foundations. That inspiration aids in authenticity, but it can also make you paranoid. After seeing such believable pandemics play out onscreen, you start to question whether they could actually happen. Soon, you’ll be afraid to catch a cold.
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10 Red Flu
The Last Ship (2014–2018) may seem like just a naval action show, but it really revolves around a worldwide pandemic. Dubbed the “Red Flu” by some parties, this disease stems from an ancient plant virus buried in the Arctic. Touch helps transmit it, but you can also get sick from breathing contaminated air. Once infected, you suffer from intense fevers and exhaustion. You then develop grotesque lesions all over your body before your system shuts down. The sickness works quickly and efficiently.
That efficacy lets the virus wipe out most of the globe. It easily erodes entire governments, leaving the world in chaos. As bad as that is, you might be more disgusted at what it does to the survivors. Several cultlike leaders use the crisis to frame themselves as saviors and seize power. As much as it bonds the navy sailors, strife of this scale also brings out the worst of humanity.[10]
9 Vampirism
It’s no secret that vampires can bite humans to turn them into other vampires. It only takes reading books like Bram Stoker’s Dracula or Anne Rice’s Interview with the Vampire or watching TV shows like True Blood or Buffy the Vampire Slayer to understand this. However, The Strain (2014–2017) boils that process down to medical science. Rather than fangs, a tendril shoots out of the monster’s mouth and latches onto its victim. It uses this tool to suck blood, but it serves another purpose as well.
Feeding on humans injects wormlike organisms into their systems. These little parasites gradually alter their organs, transforming their targets into hairless husks. Their only purpose is to serve their higher vampire masters. Starting in New York City, this biological warfare is enough to cripple the metropolis, along with the rest of the country. Suffice it to say, these vampires are a far cry from the sexy, sparkling kind.[2]
8 MEV-1
It doesn’t take a doctor to know that a film called Contagion (2011) concerns a plague. The title refers to a virus called MEV-1. This illness begins in fruit bats and pigs before jumping to humans. From there, infection from fellows is easy. The disease transfers through close contact. That doesn’t just refer to skin but also sweat, saliva, and breath. The ensuing pandemic is fraught with fever, fatigue, shortness of breath, seizures, and whatever other crippling symptoms you can imagine. After a few agonizing days, the afflicted die. Worse still, the virus maintains that speed on a global scale.
The sickness severely hinders the population. Legions of people are dead before they know it, and the remainder line crowded hospitals, pandemic shelters, and dirty streets. Although MEV-1 isn’t quite enough to topple governments or bring forth an apocalypse, it does breed desperation from both professionals and civilians. No one knows how to isolate the infection or synthesize a cure. Even when the doctors engineer a vaccine, they must figure out a means of distribution. Those hurdles ground the movie in uncomfortable realism, which only makes it more unnerving.[3]
7 Cordyceps
While The Strain grounds vampires in medical science, The Last of Us (2023– ) attempts the same for zombies. This post-apocalyptic franchise sees the Cordyceps plant fungus mutate beyond anything on record. It soon evolves enough to infect humans. Starting at their brains, it slowly morphs them into feral beasts—covered in fungal growths and focused only on killing. It goes without saying that bites can transmit the disease, but dead specimens release spores, which are arguably more effective if you breathe them. In short, the human race has no chance.
It’s not surprising that this new form of Cordyceps kills most of the planet’s population. Humanity has no idea how to combat it with science, so the only option is to fight it conventionally. This desperation turns friends and family against each other. Characters must execute their closest allies or risk getting infected themselves. Such ruthless tactics are undoubtedly isolating, but they’re the only way to survive.[4]
6 Catriona Plague
World-hopping sounds fun, but it presents a grave danger to everyone around. If travelers aren’t careful, they can introduce foreign objects into an environment, throwing off the whole ecosystem. That’s the mistake that Ciri makes in The Witcher series (2019 – ). As she jumps between worlds, she lands in a port afflicted by bubonic plague, specifically the Black Death. The residents suffer from fevers, aches, swelling, and lack of energy. A bug from this forsaken place hitches a ride on the heroine’s clothes as she teleports back, thereby heralding disaster for her own world.
The bug then jumps to a rat on a ship bound for Ciri’s homeland, and the rest is history. The sickness spreads across the Continent with little difficulty. The denizens of this medieval fantasy realm don’t have the knowledge or tools needed to combat it. Although the illness is technically nonfictional, who knows how it could mutate in the face of Elves, Dwarves, and magic? That unpredictable lethality soon fills hospitals to the brim with the dead and dying. In the end, the losses resulting from this “Catriona Plague” rival those of the war shortly before.[5]
5 Heart Virus
This sickness differs from other entries in that it only affects one person. That may sound like a walk in the park, but try telling that to the patient. Goku, the overarching hero of Dragon Ball, contracts this mysterious heart virus shortly after returning from his space travels. It gives him the usual fever and exhaustion, but it also puts him in agonizing pain. Not only is he unable to fight, but he can’t even get out of bed. That’s after taking the cure.
The virus on its own is enough to kill him entirely. Sure enough, that’s exactly what happens in an apocalyptic future. For perspective, Goku is among the mightiest warriors in the universe. He withstands the most terrible attacks you can imagine, yet this virus puts him down for the count. Normal folks wouldn’t stand a chance against such an illness.[6]
4 Simian Flu (ALZ-112)
The best intentions can easily go wrong. The Simian Flu originates as a cure. Namely, Dr. Rodman engineers it to combat Alzheimer’s, testing it on chimps to stimulate brain activity. When a test subject unexpectedly gives birth, her offspring shows immense intelligence. Unfortunately, this young chimp—dubbed “Caesar”—is soon on the receiving end of human cruelty. He retaliates by releasing an airborne version of the serum, granting similar sharpness to his fellow apes. What no one foresees is its effect on people.
The serum knocks the humans off the top of the food chain, paving the way for the modern Planet of the Apes series. The initial strain causes victims to cough up blood and eventually die. That alone eliminates most of Earth’s residents and power structures. The survivors appear to have natural immunity, but the serum is only gestating. The remaining humans eventually lose all higher brain functions, starting with their ability to speak. That downward spiral frees the apes to cage them like beasts. Oh, how the tables have turned.[7]
3 Greyscale
This dermatological disease is hard to contract and harder to get rid of. Introduced in A Song of Ice and Fire, Greyscale can only transfer through direct contact. That’s a simple prospect in itself. When a swarm of infected individuals attacks you, though, it becomes difficult to dodge. Thankfully, you can easily avoid these mobs by staying out of the areas that they frequent. Such caution is in your best interest.
Greyscale equates to slow and steady suffering. It’s generally nonfatal, but it causes children to become malformed as they grow. For adults, the sickly scales spread across the body, gradually driving the patient insane. Victims have one hope for salvation, but it only brings further pain. Treatment involves carving and peeling the scales off. This process is downright excruciating. It essentially amounts to skinning a person alive. Given that degree of torture, Greyscale is more hazardous than the titular Game of Thrones.[8]
2 Geostigma
As foreign organisms, aliens run a clear risk of infecting humans. Few invaders are more malevolent than Jenova. This extraterrestrial woman touches down prior to Final Fantasy VII. After being an unwilling test subject, her dissected corpse falls into the Lifestream: the mystical liquid infused into the planet and its people. That unholy mixture has gruesome consequences down the line.
Advent Children (2005), FFVII’s film sequel, introduces Geostigma. This sickness arises from the infected Lifestream, which spreads to the planet’s innumerable residents. Alien matter infiltrates their bodies, causing their systems to fight back with antibodies. The catch is that the bodies overcompensate and collapse. Victims then develop sores and excrete black goo before finally dying. Although anyone can contract Geostigma, it ravages the world’s children first due to their weaker constitutions. Of course, another illness inflicts much more damage in that respect.[9]
1 Infertility Epidemic
Sometimes, the simplest problems are the most difficult to solve. Children of Men (2006) provides ample evidence of that sentiment. The Infertility Epidemic does exactly what the name suggests. It renders humans unable to produce children. While the story never states the exact cause of this disease, it actively explores the ramifications. Needless to say, they are terrifying.
Society completely collapses thanks to this single issue. Extremists incite their followers to violent tactics, and governments enact totalitarian regimes to maintain control. Meanwhile, everyday people sink into hopelessness. Human beings, like any animal, have an instinct to procreate. Taking that away not only robs them of purpose, but it also prevents the species from continuing. The inevitable endpoint is extinction. That fact makes this sickness deadlier than any other.[10]