The Dancing Plague of 1518

"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, most of the people died from heart attack, stroke, or exhaustion."

Wikipedia's best guess is Mass Psychogenic Illness, or mass hysteria brought on by extreme psychological distress. Historian John Waller is the main proponent of this theory, and has written a book on what he thinks was the cause.. Bottom line: Stress collectively freaked people out, and they danced themselves to death. But I'm sure there were those who tried to blame this epidemic on the music and "loose morals" of the time..