Masked killers wielding deadly weapons and gruesome beasts with humungous fangs are scary to be sure, but what about the terror that you can’t see? Whether its fantastical, horrific, supernatural, or realistic, viruses are some of the most evil villains in the history of film.

No matter what kind of movie you like to watch, we have a list full of virus movies that are intensely scary, sharply intelligent, purely moody, and maybe even downright hilarious.

Here is Screen Rant's list of the 12 Deadliest Viruses in Movies.

28 Days Later (2002)

For all of the Romero-loving zombie purists, Danny Boyle’s reinvention of the classic movie monster in 28 Days Later was irksome, to say the least. Whether you count the assailants as zombies or not, anyone who has seen the film knows it is as objectively well-made and creative as it is subjectively jumpy and frightening. Shot with a digital camera that imbues the film with a gritty sensibility from the very first frame, 28 Days Later is not only one of the most eloquent and stylish horror movies made in the last few decades but its virus is one of the most menacing in cinema.

Four weeks after a group of animal rights activists set free an experimental virus while attempting to free chimpanzees from a laboratory testing facility, bike messenger Jim awakes from a coma to find his home of London, England apparently deserted. All too soon is he shocked to discover that, while there are people still alive around the city, most of them are heavily infected with a disease that turns them into violent, gruesome creatures. In the search for a possible cure with a group of survivors, Jim begins to realize that these infected people are not the only threat that he and his friends are up against.

The Bay (2012)

As the world has become more and more environmentally conscious, Hollywood has found a big market for ecologically centered films, which also means plenty of eco-horror movies to go with it. In The Bay, a town is slowly devoured by a breed of parasites that have mutated to a deadly degree after being inundated with chemical pollutants during July 4th celebrations in the town of Claridge, MD.

Portrayed as confiscated government footage collected and leaked to the public, the entire movie feels like a more evolved and sophisticated take on increasingly monotonous found footage horror subgenre. But at the end of the day, Oscar-winning Rain Man director Barry Levinson seems more interested in driving home the message that people who don’t live “green” are leaving themselves wide open to an excruciating death. Still, it's nice to see a more old-school approach to horror by using it as a metaphor for the worst of humanity and its deaths as the appropriate comeuppance for various social ills. As lofty as The Bay’s intentions are, it’s still creepy good fun.

Carriers (2009)

While viruses are incredibly scary things that, as made obvious by this list, make the perfect and terrifying villain for various horror movies, they are also very effective at adding dimension to otherwise snooze-worthy thrillers. Starring a pre-Star-Trek Chris Pine, Carriers fairly realistic in how it shows a contagious virus spreading across humanity… but that doesn’t mean it misses opportunities to let its deadly pandemic be scary as hell.

After a rapidly progressing fatal virus ravages the world, people are left to their own devices to survive. Brothers Brian, with his girlfriend Bobby, and Danny, with his best friend Kate, are attempting to make it across the country to an isolated spot they are all but sure is free of infection; they have a strict set of rules they are convinced will keep them all alive and healthy. But as they travel, they encounter a number of obstacles that push them beyond what they are prepared for, mentally and emotionally.

The Maze Runner: The Scorch Trials (2015)

YA-novel movie adaptations with mind-numbing and overly complex mythologies have been dominating movie theaters since the turn of the 21st century, and with the rise of the Maze Runner saga it feels as though this money-making engine will keep on chugging for a little while longer. In the franchise’s second installment, hero Thomas and the surviving members of the Glade work to free themselves from the evil adults who are harvesting teenagers' brains for the cure to the horrid "Flare," a virus that turns people into black-veined blood-thirsty freaks.

While the big-screen incarnation of the James Dashner novel is filled with cool ideas, the screenplay’s episodic structure becomes repetitive, which is only complicated by the multitude of dense ideas that make the story hard to follow. One of the true highlights of the movie though happens to be the "Flare" and its victims, known as "Cranks." The two best and most exciting scenes in the whole movie involve the courageous kid protagonists being chased by the hideous creatures through dilapidated urban cityscapes.

Cabin Fever (2002)

Since he became famous with the ultimate torture porn film Hostel, Eli Roth has really made a name for himself in the realm of cinema horror with his devil-may-care attitude towards gore and violence, which is made evermore apparent with his recent overwhelmingly brutal gross-out flick The Green Inferno. Unfortunately, people are quick to forget the auspicious beginning that got him noticed by people like Quentin Tarantino and Peter Jackson. While there is a human antagonist element to the film, Cabin Fever is one of the movies in its subgenre that really puts the viral element in the horror villain driver’s seat.

Inspired by his own (presumably less gruesome) experience contracting flesh-eating disease, Roth’s writing and directing debut follows a group college friends on a celebratory graduation trip out in the woods. In the midst of letting loose, one of the girls becomes infected with a horrible flesh-eating virus that slowly begins to spread through the rest of the group. The whole movie is fantastically nasty, but a certain leg-shaving scene followed by a dog attack is the real epitome of Cabin Fever’s gruesomeness.

Pontypool (2008)

A virus strikes a small town and turns the majority of the citizens into mindless, ravenous, violent zombies, leaving the uninfected to try and survive while their world falls to bloody pieces – sounds like your average zombie movie, right? On the surface, Pontypool might be your average day-in-the-life zombie fright fest, but in reality it is one of the most original and tense films in the realm of horror cinema.

Shock jock radio DJ Grant Mazzy and his production team are having an average day at work in their small Canadian town when reports start coming into the studio of crazed individuals going on a rampage, but what they don’t know is that town as been infected by a virus that is passed from person to person… through words. Sure, a virus transmitted by language sounds as strange when you say it out loud as it looks weird when you see it on paper, but don’t judge this movie until you had a chance to watch it. If you’re familiar with this diamond in the rough, then you already know that this masterfully tense movie is as smart and sharp as it is bone chilling.

The Stuff (1985)

There are lots of zombie-esque viruses on this list, but none of them are as blatantly weird and outside of the box as B-movie writer/director Larry Cohen’s plainly-titled The Stuff. A kooky combination of science fiction and horror, the film is one of the most original takes on zombies, using them as a metaphor for blind consumerism.

Combining the evils of classic films Invasion of the Body Snatchers and The Blob, The Stuff begins with a couple of guys finding a white, gooey, delicious substance bubbling out of the ground. Soon, the subtance is mined and is sold to the general public as an ice cream alternative called “The Stuff.” The new dessert becomes immensely popular, but there are a few who come to discover that the sweet is actually a sentient parasite that turns its consumers into mindless creatures before devouring them from the inside out. The idea is wonderfully stupid and the villain is admittedly silly, but Cohen has enough fun with the strangeness of The Stuff for it to be equally scary and funny.

[REC] (2007)

Hispanic horror filmmakers have been cornering the market on religious-based supernatural horror movies for years with champions like Guillermo del Toro and Juan Carlos Fresnadillo, but the niche is small enough that most Americans are prone to missing some of the smaller cinematic gems in this category. After the mediocre English-language remake Quarantine, most moviegoers didn’t seem to keen on trying out the Spanish original [REC], which is a huge crying shame. [REC] is a great example of a low-budget movie that retains all of the things that make found footage horror so exciting, while disposing of most of its worst clichés.

The film follows a reporter and her cameraman who following firemen for a story. After responding to a call about an old woman trapped in her apartment, the reporter, her cameraman, the firemen, and everyone else in the building also get trapped inside. Things get terrifying when they begin to be attacked by tenants who have turned vicious and start to bite anyone they see. While scrambling for their lives, the last of the living discover that they are trapped with victims of a virus believed to cause demonic possession.

Contagion (2011)

Have you ever wondered what might happen if you neglected your personal hygiene, even something as basic as washing your hands? In a star-spangled thriller directed by Oscar-winner Steven Soderbergh, Contagion takes the angle of a real-world scenario following the bird-flu-like MEV-1 virus from patient zero to global pandemic. We get to see the illnesses effects people from various points of view in all walks of life, from CDC epidemiologists and working dads to janitors and paranoid journalists.

Made at the perfect time, as more and more people are adopting huge fears of illnesses, Contagion is a stark and moody hypothetical portrait of the kind of effect such and outbreak would have on the world. While the images of societal breakdown are scary in their own right, the most grating depictions of MEV-1’s effects come from watching the physical decay of the infected. Watching Gwyneth Paltrow be overtaken by feverish hysteria and then being witness to her jarringly morose autopsy will inspire you to always keep some Purell in your back pocket.

Resident Evil (2002)

A woman wakes up after having passed out and finds her home invaded by soldiers. What she doesn’t realize is that her home isn’t a home at all, but a covert entrance for a secret subterranean biochemical weapons facility, which has seen the escape of the T-virus, a pathogen that reanimates dead bodies and turns the walking corpses into flesh-eating freaks.

When it was first released as a video game, Resident Evil was at the forefront of horror gameplay. While movies adapted from video games are notorious for being trite and overdone, this reinvention and the numerous sequels it spawned are the pinnacle of over-the-top cheesefest action movies. The bloodthirsty, goo-spewing zombies are never boring no matter how relentless or ever-present they are or what species they overtake – Milla Jovovich’s Alice fighting off zombie Dobermans is as ridiculous as it is awesome.

Splinter (2008)

Seth and Polly are heading on a camping trip when they are carjacked and kidnapped by escaped convict Dennis and his girlfriend Lacey. After getting a flat tire, the group stops at a gas station where Lacey is attacked and killed by a horrible creature covered in black spikes. Seth, Polly, and Dennis take refuge inside the gas station, but soon realize the true nature of what attacked them when they see it is a parasite that mutates its victims into dangerous, bloodthirsty hosts.

With its shoestring budget, Splinter is the perfect example of how some ingenuity and a good bit of resourcefulness can accomplish wonderfully horrible things. With a small cast, minimal locations, and cleverly designed make-up and effects, the film is very successful, especially when it comes to the gore and the scares. It is incredibly helpful to the overall effect that the monsters are very original, borrowing only the best elements from other simple, albeit richly interesting horror movies, like 2001’s Jeepers Creepers.

Black Sheep (2006)

Since his childhood, Henry has always been afraid of sheep. Trying to distance himself as much as he can from the fluffy quadrupeds, Henry comes home to New Zealand to sell his portion of the family sheep farm the first chance he gets. Unbeknownst to him, Henry finds out that his brother Angus has begun experimentation to breed the perfect sheep to dangerous consequences – the poor animals have been turned into flesh-hungry zombie sheep. Now Henry has to figure out how to conquer his fear and stop the spread of a virus in a country where sheep outnumber people seven to one.

Black Sheep is a great horror movie with an incredibly inventive zombie virus at its center, one that is as bloody as it is hysterical. Evil sheep are funny in their own right, but when those sheep bite people and turn them into humanoid-sheep hybrid zombies you reach a whole new level of humor. Not to spoil the ending, but there is no horror movie finale that is as brilliantly goofy.

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If we forgot any awesomely horrible movie viruses, let us know with a post in the comments section!