This is one of the most mysterious cases of mass hysteria in the history of Europe. Actually, it remains unexplained even to this day.
In July of 1518, local woman, Frau Troffea began to violently dance in the streets of the city of Strasbourg, France. There was no music and her face showed no expression of joy. She appeared unable to stop herself from her frenzy.
If this was an isolated incident, the city elders may have attributed it to madness or demonic possession, but soon after Troffea began dancing, a neighbor joined in. And then another one. By the end of a week more than 30 people were dancing day and night on the streets. And it didn’t stop there. By the time a month had passed, at least 400 citizens of Strasbourg were swept up in the phenomenon.
Doctors were called when some of the dancers began dying from heart attacks, exhaustion, or strokes. For some inexplicable reason, the doctors believed that the cure for the dancing was even more dancing, so they erected a wooden stage for the dancers, and musicians were called in. Bit by bit the dancers stopped, and the dancing ended as mysteriously and unexpectedly as it began.
This may sound like some archaic bit of folklore, but the dancing plague of 1518 is mentioned in medical, civic, and religious notes of the time.
There are a lot of theories trying to explain the mysterious phenomenon. According to one of them, the dancers were victims of mass hysteria: instances when more than one person believes they are afflicted by an identical malady — often during times of extreme stress within the affected community. The Strasbourg incident occurred during a time of rampant famine and malnutrition and subsequent deaths. But could this happen to more than 400 people simultaneously?
A second theory is in the realm of agriculture. The condition called Ergotism occurs when grains of rye are attacked by a specific mold. Eating the infected rye can lead to seizures, although the movements of Strasbourg’s afflicted looked much more like traditional dancing than seizures of any sort.
Another theory suggests that the dancing plague was in result of some kind of religious ecstasy caused by veneration of Saint Vitus, the patron saint of epilepsy.
However, neither theory is proven and the dancing plague remains a complete mystery.