The “Dancing Plague” of 1518 was a mania that lasted a month and killed dozens of people in Strasbourg, Alsace (then part of the Holy Roman Empire) in July 1518 through exhaustion or heart attack. People just danced uncontrollably until they collapsed!
The outbreak began in July 1518, when a woman, Mrs Troffea, began to dance fervently in a street in Strasbourg. This lasted somewhere between four to six days. Within a week, 34 others had joined, and within a month, there were around 400 dancers, predominantly female. Some of these people eventually died from heart attacks, strokes, or exhaustion.
Historical documents, including “physician notes, cathedral sermons, local and regional chronicles, and even notes issued by the Strasbourg city council” are clear that the victims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.
One other famous case involved people dancing on a bridge. Eventually so many people danced that they broke the bridge and fell into the river.