St. Vitus's dance

Pick up a textbook on abnormal psychology and in the first chapter you are likely to find a discussion of the dance manias. Also known as St. Vitus's dance, between the eleventh and seventeenth centuries, manias swept across Europe as tens of thousands of people participated in frenzied public orgies and wild dances lasting for days and sometimes weeks. It is little wonder why psychiatrists and medical historians classify such episodes as group mental disorder affecting those overwhelmed by the stresses of the period. During outbreaks many immodestly tore off their clothing and pranced naked through the streets. Some screamed and beckoned to be tossed into the air; others danced furiously in what observers described as strange, colorful attire. A few reportedly laughed or weeped to the point of death. Women howled and made obscene gestures while others squealed like animals. Some rolled themselves in the dirt or relished being struck on the soles of their feet.

http://www.csicop.org/si/2000-07/dancing-mania.html