In July 1518, residents of the city of Strasbourg (then part of the Holy Roman Empire) were struck by a sudden and seemingly uncontrollable urge to dance. The hysteria kicked off when a woman known as Frau Troffea stepped into the street and began to silently twist, twirl and shake. She kept on dancing for nearly a week when several men were compelled to join in. Within days, a large number of people joined her, dancing for hours, days, or even weeks. Local doctors proclaimed the source of the condition as ‘hot blood’, but gave no explanation as to what that means. The town council responded by building a stage, bringing in more dancers and supplying a band. This, of course, inspired more participation. Soon the activity began taking a toll physically on the dancers.
Some official reports described exhaustion, strokes and heart attacks being experienced by the crowd. The event lasted into September. The council later sent the affected dancers to a shrine for St. Vitus, believing the dancing was a religious issue. The dancers were required to pray for absolution. According to historian John Waller, the explanation most likely concerns St. Vitus, a Catholic saint who pious 16th-century Europeans believed had the power to curse people with a dancing plague.
The exact number of fatalities remains uncertain due to the inaccuracy of historical records. It is believed the death toll was in the neighborhood of 400 people. One theory for the event is that the dancing plague was a form of mass hysteria, where the behavior of one person could trigger others to act in the same manner. Another theory suggests that the outbreaks might have been caused by ergot poisoning, which can lead to convulsions and hallucinations. Some historians have suggested the dancers were members of a religious cult performing a demonic ritual.
Dancing plagues were not isolated to Strasbourg. Similar outbreaks occurred in other parts of Europe during the 14th and 16th centuries. One of the earliest known outbreaks took place in Aachen in 1374. Contemporary historians suggest that the outbreaks were likely caused by a combination of factors, including stress, superstition, and potentially mass psychogenic illness. 

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