Dancing mania. In July 1518, Frau Troffea began dancing in chaotic fervour on the streets of Strasbourg. She danced for a week straight, and soon others joined her. Within a month, the Dancing Plague of 1518 claimed between 50 and 400 victims. Historical sources make it clear the victims danced, but why they did so remains unexplained. Mysterious outbreaks had occurred before: in 1020s Bernburg, Germany, a Christmas Eve service was disturbed when revellers inexplicably danced around the church. In Aachen, 1374, a large-scale outbreak was recorded that spread to Cologne, Flanders, Hainaut, Strasbourg, Utrecht and other towns. In 1428 in Schaffhausen, a monk even danced himself to death.