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A Fire Beneath the Skin


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Fantastical Biology – Part Eight: Fantasy Diseases

Bacteria by Unknown ArtistWhen creating a believable fantasy world, we often focus on things like politics, religion, culture; but there’s a tiny (microscopic, in fact) detail that can flesh out a story world and be used to create tension and conflict. Protagonists in fantasy novels often get cuts and bruises, or spend a few nights camping in the cold, drinking from ponds they hope are safe. Sometimes they worry about infections, but more often they just wrap a piece of their dirty, sweaty shirt around the cut and continue on their way. We usually don’t read about the part where they get a raging infection from the cut, and a case of the runs from the pond water, and what this does to their ability to fight. And so, this Fantastical Biology article will take a look at the tiny creatures that can do more damage to a stalwart knight than any dragon could.

Bacteria vs. Viruses

Virus by studio XVIVOMost diseases are caused by either bacteria or viruses. Bacteria are single-celled creatures that live in our bodies: some are good, others cause illness. Unlike bacteria, we’re not entirely sure that a virus is actually a living creature. It uses the cells of living organisms to make copies of itself, essentially using our own cellular machinery against us. A virus can infect pretty much anything, including bacteria.

Traditional fantasy is usually set in a time equivalent to our own middle ages in terms of technology, but there’s no rule saying a fantasy society can’t have more modern medical knowledge. And your story world’s diseases don’t have to be caused by microscopic organisms, either. Ancient Greeks believed that diseases were caused by imbalances in bodily fluids called humors. Traditional Chinese medicine also uses the idea that disease can be caused by imbalances in the body. Since this is fantasy, disease could be caused by magic as well, either by a spell designed to make someone sick or even from using magic at all.

Terrible Ways to Go

You Have Died of Dysentery from Oregon TrailDrawing from history isn’t a bad way to add some infectious agents to your fantasy setting. Here I’ll cover some of the most common (and devastating) diseases throughout human history, and ones most likely to be found in the traditional fantasy setting. First is cholera and dysentery. They have similar outcomes for the patient: deadly dehydration due to excessive diarrhea. They arise from unsanitary living conditions, so if a fantasy city is lacking a well-maintained sewer system, there’s a good chance the population might suffer from an outbreak of these infections.

Small pox has plagued humanity for millennia, though has thankfully been eliminated today. It is estimated that it killed 400,000 Europeans a year by the end of the 18th century. Those who survived often had scars on their face, and many suffered from blindness as well. This one sees some mention in fantasy novels, particularly those inspired by Medieval Europe.

If you’re looking for inspiration for a more adult-themed disease, syphilis is an STD with many cultural ramifications. Those who had it were often pariahs, both from the physical disfigurements (those who were infected for a long time often suffered from nasal collapse and had to get artificial noses) and society considering them sexual deviants. One thing to consider when creating a disease for a fantasy world is the effects on those who are infected. Does infection change the way the patient looks physically, or would the method of infection make them social outcasts?

Bubonic Plague in London Woodcut 1600s

The Black Plague might be the most well-known pandemic in history. It passed across Asia and into Europe during the 1300s. There are varying estimates as to how deadly the plague was, but some cities lost around 50% of their population in a matter of months. The Black Plague is what’s called a zoonotic disease, meaning it moves from animals to humans. There are many diseases transmitted this way, such as bird and swine flu. Fantasy creatures interacting with one another in a novel could pass diseases as well. If your human protagonist gets bit by a faerie, what sort of symptoms might they have? Is it as mild as a cold, or might there be Faerie Rabies that they need to get treatment for immediately?

Seeking Treatment

Healing by Wen-MIf an intrepid adventurer happens to catch Faerie Rabies while traipsing through their forest realm, how exactly are they going to get rid of it? That’s going to depend on how advanced the story world’s medical care is. The ill could seek help from the town witch, or a doctor who may or may not dabble in spells. There are already a couple of great articles on Fantasy-Faction about medicine in fantasy (here is part 1 and part 2), and I recommend taking a look at those for some good ideas.

Many fantasy novels mention the sorts of medical treatments that are familiar to westerners, but Middle Eastern and Asian civilizations made great advancements in medicine in ancient times, and any writer wanting to add some detail to their world’s medicine could also look there for inspiration.



  1. Avatar Joie says:

    I would love to read a fantasy book exploring the vast potential of diseases. Too bad it seems to be relegated to sci-fi.

  2. Avatar Jon_Anon says:

    Makes me think of Blight in Morrowind

  3. Avatar Erica says:

    Nice entry. I’m a biologist by training, so I love me a good disease and tend to have healers as characters in my stories. I usually stick with ones that are real-world ailments, or at least based on them, but sometimes it’s fun to invoke a malaise that’s a bit more magical in nature.

  4. […] My latest post on Fantasy Faction is about diseases in fantasy stories (or the lack thereof) and some ideas on how to incorporate them into setting and plot. […]

  5. Avatar Nicole says:

    “Faerie Rabies” is something you need to explore for the benefit of all humans who like to read.

    Interesting read and great related links. Thank you!

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