Dancing Plague, also known as Dancing Mania, was a phenomenon involving people, sometimes hundreds or thousands of people, dancing uncontrollably. There were many occurrences of the Dancing Plague that took place in Europe between the 14th and 17th centuries. They danced for hours, days, sometimes even weeks and months.
Dancing Plague most often broke out during times of hardship. The people afflicted would dance erratically and enter a state of trance or unconsciousness, unable to control their movements. Many people suffered from broken ribs, hallucinations, and epileptic fits. A well documented outbreak was in the city of Strasbourg in July of 1518. A woman began dancing in the street and continued for days. In a week she had been joined by 100 people who could not stop dancing. There were 400 people afflicted by the epidemic by the time it receded in September 1518, many of whom had heart attacks and died because of the plague.
Contemporary historians and scientists have many theories as to what caused it. A prominent theory is that those afflicted had ergot poisoning, but that would not account for all the symptoms. Another theory is that the events were staged by religious cults. While it is unclear if this was a real illness or a human phenomenon, many agree that the Dancing Plagues were the first large occurrences of mass hysteria.