Sometime in mid-July 1518, in the city of Strasbourg, a woman stepped into the street and started to dance.
She was still dancing several days later. Within a week about 100 people had been consumed by the same irresistible urge to dance. The authorities were convinced that the afflicted would only recover if they danced day and night.
So guildhalls were set aside for them to dance in, musicians were hired to play pipes and drums to keep them moving, and professional dancers were paid to keep them on their feet. Within days those with weak hearts started to die.
By the end of August 1518 about 400 people had experienced the madness. Finally they were loaded aboard wagons and taken to a healing shrine. Not until early September did the epidemic recede.
This was not the first outbreak of compulsive dancing in Europe. In fact, there had been as many as ten dancing epidemics before 1518, one in 1374 engulfing many of the towns of modern day Belgium, north-eastern France and Luxembourg.
The 1518 case is simply the best documented and by a richer variety of sources than its predecessors. It was not the first, though it was almost certainly the last to occur in Europe.
How do we explain this bizarre phenomenon? A popular idea has been that the dancers had ingested ergot, a psychotropic mould that grows on stalks of rye. But this is highly unlikely. Ergotism can trigger delusions and spasms, but it also typically cuts off blood supply to the extremities making coordinated movement very difficult.
It's also been suggested that the dancers were members of a heretical cult. This is also improbable because contemporaries were certain that the afflicted did not want to dance and the dancers themselves, when they could, expressed their misery and need for help. What's more, there was no suggestion of treating these people as heretics.
The other main contender is that this was an outbreak of mass hysteria. This is far more plausible, especially because in 1518 the poor of Strasbourg were experiencing famine, disease and spiritual despair on a scale unknown for generations.
But in itself this theory doesn't explain why the people danced in their misery.
3. set aside駁回