Vampires
One dark and stormy evening, Spanish neurologist Juan Gomez-Alonso was watching a vampire movie when he realized something strange; he noticed that vampires behave an awful lot like people with rabies. The virus attacks the central nervous system, altering the moods and behaviors of those infected. Sufferers become agitated and demented, and, much like vampires, their moods can turn violent.
Rabies has several more vampire-like symptoms. It can cause insomnia, which explains the nocturnal portion of the legend. People with rabies also suffer from muscular spasms, which can lead them to spit up blood. What's stunning is the fact that these spasms are triggered by bright lights, water, mirrors, and strong smells, such as the scent of garlic. (Sound familiar?) After watching the Dracula movies a few more times, Dr. Gomez-Alonso felt compelled to continue studying vampire folklore and the medical history of rabies. Eventually, he discovered an even more profound connection between the two phenomena: Vampire stories became prominent in Europe at exactly the same time certain areas were experiencing rabies outbreaks. This was particularly true in Hungary between 1721 and 1728, when an epidemic plagued dogs, wolves, and humans and left the country in ruins. Gomez-Alonso theorized that rabies actually inspired the vampire legend, and his research was published by the distinguished medical journal Neurology in 1998.
The Madness of King George
Dr. Gomez-Alonso wasn't the first scientist who tried to pin vampirism to a real illness. In 1985, Canadian biochemist David Dolphin proposed a link between vampires and porphyria — a rare, chronic blood disorder characterized by the irregular production of heme, an iron-rich pigment found in blood. The disorder can cause seizures, trances, and hallucinations that last for days or weeks.
As a result, people with porphyria often go insane. (Britain's King George III, the one who inspired our founding fathers to start their own country, is thought to have suffered from it.) Porphyria sufferers also experience extreme sensitivity to light, suffering blisters and burns when their skin is exposed to the sun. Another symptom of porphyria is an intolerance to sulfur in foods. Which food contains a lot of sulfur? That's right, garlic.
Werewolves
In addition to explaining away vampires, medicine also has some answers for werewolves. In The Werewolf Delusion (1979), Ian Woodward explains that rabies may have also inspired the werewolf myth.
Rabies is transmitted through biting, and the dementia and aggression of late-stage rabies can make people behave like wild animals. Now, imagine that you are living in a village in medieval Europe and you see your friend get bitten by a wolf. A few weeks later, he starts foaming at the mouth, howling at the moon, and biting other villagers. Suddenly, that story your grandmother told you about the Wolfman sounds like a decent explanation for what's going on.
Zombies
Zombies may also be creatures of science, at least according to Costas J. Efthimiou, a physicist at the University of Central Florida. In 2006, he attempted to explain the mysterious case of Wilfred Doricent, a teenager who died and was buried in Haiti, only to reappear in his village more than a year later, looking and behaving like a zombie. Efthimiou concluded that Wilfred was not the victim of a curse, but of poisoning. In the waters of Haiti, there is a species of puffer fish whose liver can be made into a powder, which has the ability to make a person appear dead without actually killing him. Wilfred may have been poisoned with the powder and then buried alive.
According to one of Dr. Efthimiou's theories, once underground, Wilfred suffered from oxygen deprivation that damaged his brain. When the poison wore off and Wilfred woke up, he clawed his way out of the grave. (Graves tend to be shallow in Haiti.) Brain-damaged, he wandered the countryside for months until he ended up back in his village.
After Dr. Efthimiou published his explanation of the case, Dr. Roger Mallory, a neurologist at the Haitian Medical Society did an MRI scan of Wilfred's brain. Although the results were nonconclusive, he found that Wilfred's brain was damaged in a way that was consistent with oxygen deprivation. It would seem that zombification is nothing more than skillful poisoning.
This article originally appeared in mental_floss magazine.