Zombies and vampires make for pretty good horror stories: both monsters feed on flesh or blood, and their bites turn victims into zombies and vampires themselves. But the scariest thing of all? Both myths have a few things in common with a real-world nightmare: rabies.

Rabies is an infectious disease that’s primarily spread through the bite of an infected animal, like dogs or raccoons. The virus spreads from the bite to the brain, where it’s devastating: victims can experience anxiety, hallucinations, muscle spasms, increase in saliva, seizure, and comas. People can also become aggressive. Within a few days of these symptoms, almost 100 percent of rabies victims die, likely from respiratory failure.

Almost 100 percent of rabies victims die

Today, we have vaccines that can prevent people who are bitten from dying. (The shots are usually given after exposure, though some people who routinely work with animals can get preventative shots as well.) But these vaccines — for people and animals — aren’t available all over the world. Rabies still kills tens of thousands of people every year, mainly in Asia and Africa, where it’s mostly transmitted by rabid dogs.

Rabies has been around for thousands of years: there are references to it in Sumerian writing, as well as in ancient Greek medical texts. And it’s often been used metaphorically to describe an animal rage that can sometimes infect humans, says Bill Wasik, author of the book Rabid, which charts the history of the disease. In Homer’s Iliad, the Trojan warrior Hector experiences this murderous rage the Greeks called “lyssa” — the same word used to describe rabies in medical texts. Culturally, the disease fed into these fears of animalistic possession, which are often motivating forces in storytelling, Wasik says. Those same fears and anxieties are reflected in the myths about vampires, zombies, and even werewolves.

“What you find with all those myths,” says Wasik, “is that they’re channeling these deep anxieties about what separates humans from animals, the circumstances where we feel like we’re not in control, circumstances where blood lust or literal lust or so on overwhelms our seeming rationality.”

Some studies have pointed out striking similarities between the symptoms of rabies and historical descriptions of vampires and zombies. For example, vampires were thought to wander at night and attack women, while rabies can make its victims sleepless and aggressive, according to a 1998 study published in Neurology. And vampires were believed to turn into dogs or bats, the two animals that most commonly carry the disease. Another study published in 2013 spells out the parallels between zombies and rabies: zombies are imagined to be as aggressive as rabid animals, with similar drool problems; and they sometimes hobble, mimicking the convulsions of rabies victims.

“culturally suggestive links”

It’s a bit of a stretch to say that myths about vampires and zombies literally derived from rabies patients, Wasik says. Both legends have changed greatly through time: for instance, vampires weren’t contagious way back when, according to Wasik. But there are definitely “culturally suggestive links” between rabies and all these myths. In the past, when we didn’t know how the disease spread or how to protect ourselves, cases of rabies might have inspired the legends, as a way to make sense of what was happening. In the 1720s, for instance, there was a major epidemic of rabies in dogs, wolves, and other wild animals in Eastern Europe, where vampire legends flourished, according to the Neurology paper.

Whether or not rabies really gave rise to vampires and zombies in the past, we definitely know the disease is a source of inspiration today: director Danny Boyle said that the virus that turns people into zombies in his 2002 horror movie 28 Days Later was modeled in part on rabies.

Did you just get some inspiration for your Halloween costume?