The Dancing Plague (or Dance Epidemic) of 1518 was a case of dancing mania that occurred in Strasbourg, France (then part of the Holy Roman Empire) in July 1518. Numerous people took to dancing for days without rest, and, over the period of about one month, some of the people died from heart attack, stroke, or exhaustion.

In July of 1518, a woman referred to as Frau Troffea stepped into a narrow street in Strasbourg, France and began a fervent dancing vigil that lasted between four and six days. By the end of the week, 34 others had joined her and, within a month, the crowd of dancing, hopping and leaping individuals had swelled to 400.

Authorities prescribed "more dancing" to cure the tormented movers but, by summer's end, dozens in the Alsatian city had died of heart attacks, strokes and sheer exhaustion due to nonstop dancing.

For centuries this bizarre event, known variously as the dancing plague or epidemic of 1518, has stumped scientists attempting to find a cause for the mindless, intense and ultimately deadly dance. Historian John Waller, author of the forthcoming book, "A Time to Dance, A Time to Die: The Extraordinary Story of the Dancing Plague of 1518," studied the illness at length and has solved the mystery.

"That the event took place is undisputed," said Waller, a Michigan State University professor who has also authored a paper on the topic, which has been accepted for publication in the journal Endeavour.

Waller explained that historical records documenting the dancing deaths, such as physician notes, cathedral sermons, local and regional chronicles, and even notes issued by the Strasbourg city council during the height of the boogying rage, all "are unambiguous on the fact that (victims) danced."

"These people were not just trembling, shaking or convulsing; although they were entranced, their arms and legs were moving as if they were purposefully dancing," he said.

Dancing Plague of 1518