Although it never became as famous as the other great plagues of Europe, sweating sickness was one of – or perhaps several of – the deadliest diseases of the medieval era.

Although it never became as famous as the other great plagues of Europe, sweating sickness was one of – or perhaps several of – the deadliest diseases of the medieval era.

The sweating sickness, often known as English sweating sickness, describes a series of similar and highly deadly epidemics which began in the 1400’s, declined in lethality over a century or so, and final disappeared around the mid 1500’s. Unlike the Black Death, which we think we’ve probably identified, 500 years of stud hasn’t been enough for us to figure out what actually caused sweating sickness. Many hypotheses have been put forth, including anthrax and tick bites, but the current leading theory is that it was a manifestation of hantavirus. It’s entirely possible that different outbreaks had different causes, in spite of their similarity, and it’s very possible that the reason we can’t identify the disease is that it was caused by a bacteria or virus that no longer exists and has therefore never been observed.

Sweating sickness would appear suddenly and without any apparent cause. Some historical evidence suggests that the disease had an incubation period of about 30-40 days, meaning that a month would pass between a person becoming infected and first developing symptoms. Within hours of symptoms starting, afflicted individuals developed chills, tremor, and a high fever. This rapidly progressed to a generalized weakness. The victim would sweat profusely, to the point that dehydration could set in. Nearly half of all infected people allegedly died, with estimates from different epidemics and locations ranging from 5% to 90%. It isn’t clear what the exact cause of death was; high body temperature is itself very rarely dangerous, but diseases that raise the temperature so precipitously may be associated with muscle breakdown leading to kidney failure, or autonomic instability leading to cardiovascular collapse. Then again, this was an illness we can’t identify and the actual cause of death could have been something else entirely. If the sufferer lived, symptoms often abated and vanished within a day, resulting in a full recovery. Unlike many infections, surviving a single episode seems not to have conferred immunity, and many people died from their second or third bout with “the sweat.”

Sweating sickness seems to have been transmissible between humans, which is interesting in so far as most of the modern diseases that it resembles don’t spread between humans easily. It’s equally possible that the disease spread by some other vector; humans traveled along with countless rats and fleas, and European cities were filth-ridden plague-pits at the best of times in that era.

The disease had a number of peculiar features. Most famously, although there were outbreaks outside of England, several writers independently documented that, in England, only English people seemed to fall ill, and never foreigners. Any reader of fantasy and science fiction will immediately see the storytelling potential of something like that. Also interestingly, sweating sickness was one of those curious diseases which seems to have preferentially hit, not the weak and infirm, but the healthy and middle-aged. It cut a swathe through the professionals and artisans, which could leave a city destabilized and disrupted. It may have affected the middle and upper classes more than the poor, as well.

We don’t have records of many of the treatments used during the epidemics, but at least a few authors records that physicians would recommend putting the ill individual to bed, closing the windows, and keeping them as warm as possible. Given that this presumably only further raised their body temperatures, I would love to know what the rationale for this was, but the reasoning is, alas, lost to history.

Sweating sickness is of obvious use in a game setting in part because we know little about it, but have rich and detailed descriptions of how horrific it was. The disease leaves a lot of room for the storyteller’s imagination. In particular, the storyteller has a lot of room to play with the disease’s cause; it behaved so atypically compared to many other real illnesses that it’s easy to see how people could have observed an intelligent hand at work. I sort of like the idea that the sweating sickness was being actively propagated by an evil spellcaster for a hundred years, or was the result of some vile tome of black magic being found by hapless adventurers every few years who would unintentionally trigger a new outbreak. 

More than four years ago, Dr. Eris Lis, M.D., began writing a series of brilliant and informative posts on RPGs through the eyes of a medical professional, and this is the one that appeared here on November 21, 2015. Lis is a physician, gamer, and author of the Skirmisher Publishing LLC OGL sourcebook Insults & Injuries, which is also available for the Pathfinder RPG system.