Not many people have heard of the strange and inexplicable illness, Sudor Anglicus and the Dancing Plague, but they really did exist in the middle ages. Over the course of the history of mankind, each era had its own set of health problems – often claiming many victims. These usually came about abruptly and were gone soon afterwards. Scientists have come up with several theories, but they have yet to find their actual cause.


Sudor Anglicus (sweating sickness)

First appearing in Wales, 1485, the mysterious infectious disease soon reached London. It spread through all of England like wild fire, and it reached the Scottish and Irish borders – but suddenly stopped there. Later, it got all over Northern-Europe, the Low Countries, Scandinavia and even Russia. The last and most severe epidemic in 1551 did considerable damage in the English population. With five epidemics, this disease claimed the lives of 3 million people.

The disease spread quickly, with a short latency period. Its symptoms came on abruptly and unbelievably strong. No surprise, then that it caused great panic in Henry VIII and the Tudors, as well as the frightened population. This situation benefited John Kays, an English physician, who used uncertain treatments without results purely for profit on his wealthier patients. He was the first person to describe the sweating sickness in detail as well. ‘… The exterior is calm in this fever, the interior excited… the heat in the pestilent fever many times does not appear excessive to the doctor, nor the heat of the sweat itself particularly high… But it is on account of the ill-natured, fetid, corrupt, putrid, and loathsome vapours close to the region of the heart and of the lungs whereby the panting of the breath magnifies and increases and restricts of itself…’

The name of the disease comes from the foul-smelling sweat of patients. They lost most of their liver and kidney function, perhaps responsible for the odour and breath. Kayes advised with his current understanding of medicine that patients should stay away from dense fogs and rotten fruit; regular exercise and herbal teas were also prescribed. Unsurprisingly, these didn’t help cure the disease.

What is surprising, however, is that it was quite selective when it came to age, gender and social status. The most common victims were healthy men and those either too rich or poor. There have been many theories about its actual pathogen. It’s been suggested that it might be a flu epidemic, or perhaps bird flu, as sometimes the poultry also passed away simultaneously. Lung anthrax and typhoid also came up, but these remained only theories until in 1993, an epidemic among Navaho people had very similar symptoms. It turned out to be a respiratory hanta virus. In 2001, scientists have excavated graves of those that died of sweating sickness to try and isolate the pathogen, but these attempts have so far been unsuccessful. There’s also no explanation as to what exactly stopped its spread, but one idea has been climate change, making circumstances unfavourable for the pathogen.

This disease appears in theatre as well, for example, in Shakespeare’s Henry IV, Sir John Falstaff passes away from it.


The dancing plague

The outbreak began in July 1518, when a woman, Frau Troffea, began to dance fervently in a street in Strasbourg. This lasted somewhere between four and six days. Within a week, 34 others had joined, and within a month, there were around 400 dancers, predominantly female. Some of these people died from heart attacks, strokes, or exhaustion. One report indicates that, for a period, the plague killed around fifteen people per day. However, the sources of the city of Strasbourg at the time of the events did not mention the number of deaths, or even if there were fatalities. 

Historical documents, including “physician notes, cathedral sermons, local and regional chronicles, and even notes issued by the Strasbourg city council” are clear that the victims danced. It is not known why these people danced, some even to their deaths.

As the dancing plague worsened, concerned nobles sought the advice of local physicians, who ruled out astrological and supernatural causes, instead, announcing that the plague was a “natural disease” caused by “hot blood”. However, instead of prescribing bleeding, authorities encouraged more dancing, in part by opening two guildhalls and a grain market, and even constructing a wooden stage. The authorities did this because they believed that the dancers would recover only if they danced continuously night and day. To increase the effectiveness of the cure, authorities even paid for musicians to keep the afflicted moving. The strategy was a disaster; after those policies were applied the illness underwent a dramatic growth. Performing dances in more public spaces facilitated the spread of the psychic “contagion”.

Similar cases have been reported from Erfurt in 1247, and Maastricht as well.

Its cause remains a mystery, but one theory is ergotism. This, much like LSD, causes severe hallucinations and seizures, as well as trouble with the arms’ and legs’ blood supply. The problem with this explanation is that ergotism comes with co-ordinational issues as well, making the patients incapable of dancing for days, let alone weeks. It’s also highly unlikely that a single psychotropic substance should provoke the same reaction from more people in the same group.

Another theory is mass hysteria. Because of famine, floods, wars, epidemics like the black plague had taken their toll on people’s psyche. Fear and desperation could have lead to mass hysteria, which could have been the basis for an equally drastic psychological reaction. Only religion was seen as the cure, so people suffering from the disease prayed for salvation to Saint Vitus. By the 17th century, Europe had had its last dancing plague.

From the dark middle ages, these two are among the most fascinating and mysterious diseases, with causes still to be discovered.