Eeek! The actual diseases that inspired vampires, werewolves, and zombies

With Halloween's arrival, scary monsters and frightening displays are up in houses and stores everywhere.  But where did these monsters come from? Were they simply from a vivid imagination, or could they be real?  In fact, the mythologies of these monsters may be partly explained from the history of medicine. Let's consider three common monsters that may have real origins.

From the prototypical Dracula to modern depictions in Twilight, vampires have always captivated our imagination. We know them as pale humanoids that thirst for blood and avoid the sun. They are deterred by garlic, and transmit their vampire disease to other humans through bites, generally to the neck.

Let's break that down medically. What real medical disease could vampires represent?

First, there's sensitivity to light, otherwise known as photosensitivity, which can be seen in many medical conditions, including autoimmune diseases like lupus. Other skin conditions, such as drug reactions, can be triggered by the sun, or appear only in areas of the body exposed to sunlight.

The one disease most often suggested by scholars to explain vampires is porphyria. Porphyrias are a group of mostly inherited diseases caused by defects in making heme, a key component of the hemoglobin in our red blood cells. In different types of porphyria, an affected person may be photosensitive due to accumulated porphyrin molecules in the skin.  These molecules cause extreme sensitivity to light, which may lead to pain, blistering, and scarring, so affected patients are advised to avoid the sun. In one form called erythropoietic porphyria, these molecules can also accumulate in bones and teeth, causing red-stained teeth that could make someone look like he'd been drinking blood.

Since these patients have poor stores of normal heme, you might even think that drinking the blood of another person could be a real way to replenish their own blood's heme supply. In reality, though, drinking blood would not help, and ironically, the treatment for some types of porphyria, such as porphyria cutanea tarda, is actually phlebotomy or bloodletting, which removes the toxic molecules from the body. Lastly, people suffering from porphyria are advised to avoid garlic, as its sulfites can actually worsen symptoms.

As for vampire bites transmitting the disease, that mythology cannot come from porphyria, which is not contagious, but could be explained by an infection, such as rabies.  Rabies is a viral infection, mostly seen in raccoons, bats, skunks, and foxes, which causes aggressive behavior and can be transmitted by bites.

Like all myths, werewolf origin stories vary in their explanations. As depicted in the classic The Wolf Man, werewolves are created when an existing werewolf bites a human, ostensibly transferring werewolfism as an infectious disease. On the other hand, some depictions (see: Teen Wolf) make the disease an inherited one, perhaps with delayed onset in puberty. Regardless, werewolves can change back and forth from monster to human form, undergoing metamorphosis into hairy, aggressive, ruthless beasts only when exposed to moonlight or under a full moon.

As with vampires, werewolves are likely inspired by some combination of rabies and the porphyrias. As previously mentioned, rabies is transferred by the bite of wild animals, which certainly sounds just like the story of how werewolves are made. Since rabies directly affects the central nervous system, it can cause brain disease with confusion, hallucinations, hypersalivation, and hydrophobia (fear of water). Porphyrias, which limit people from the sun, can cause some excess hair growth as well as disfigured skin and teeth.

Other real diseases may cause excess hair growth, though no disease is known to cause sudden rapid hair change in seconds or minutes. Hypertrichosis lanuginosa is a disease of hair covering the entire body (think: Cousin Itt from The Addams Family).  Inherited forms of hypertrichosis (excess hair) have been described historically as dog-men and wolf-men, and their families documented with such findings over generations. Though also rare, an acquired form of hypertrichosis lanuginosa can occur in reaction to an underlying cancer in the body.  This is known as a paraneoplastic syndrome (manifestation of an underlying cancer), most commonly reported with colorectal cancers.

Should you fire a silver bullet to kill a werewolf?  It's hard to find any association of silver with any of the diseases mentioned. However, historically, silver (like silver sulfadiazene) has been used to treat wounds, and before the advent of antibiotics, colloidal silver (silver particles suspended in liquid) was used as a disinfectant.  More recently, silver has been used as a homeopathic treatment for a number of infectious diseases, but don't try it. These claims are not evidence-based, and silver accumulated in the body can cause real problems, like argyria).

Zombies, also known as the undead, were originally explained simply as reanimated human corpses. In the late 20th century, newer depictions of zombies (from George Romero's classic Night of the Living Dead to modern films and television such as 28 Days Later and The Walking Dead) feature humans transformed into the monsters from an infectious disease. The latest versions of zombies also emphasize zombies as monsters that thirst to eat brains. In all forms of zombies, the monsters are mindless beasts that impulsively try to attack other humans.

From a medical point of view, the mindlessness of these creatures suggests a psychiatric or brain disease, since motor control is intact, but cognition is completely gone. Several infectious diseases can target the brain, from Zika virus (which may target fetal brain tissue) to prions (the insidious cause of mad cow disease). Prion diseases develop slowly over decades, so to cause a sudden zombie outbreak with rapid contagiousness, zombie-ism would almost certainly need to be caused by a virus or perhaps bacteria.

Fortunately, no disease reported in medical literature is known to cause people to want to eat other people's brains. However, the prion-caused brain disease kuru did spread among one tribe in Papua New Guinea because of the tribe's cannibalistic tradition to eat dead members' brains as part of funeral rituals.

Regardless of whether you believe a zombie attack could be near, the U.S. Centers for Disease Control and Prevention (CDC) took the possibility of an infectious outbreak sort-of-seriously, publishing a 2011 guide, "Preparedness 101: Zombie Apocalypse."

Jules Lipoff, M.D.,  is an assistant professor of clinical dermatology in the Perelman School of Medicine at the University of Pennsylvania.