In July 1518, Frau Troffea stepped into a Strasbourg street and began to dance. She could not stop.

She danced until she dropped, rested, then started again. Her husband begged her to quit. The next day she was back on swollen, bloody feet.

Within a week, more than 30 people had joined her.

How do you treat a dance that will not stop?

Local doctors blamed "hot blood." The authorities decided the sick should keep dancing until the illness burned itself out.

They turned that advice into a public cure. They opened halls, hired musicians, and sent professional dancers to keep the afflicted moving.

Instead of rest, the exhausted were given more dancing.

The plan made the outbreak worse. By some accounts, as many as 400 people were caught up in it by August. The true number is still disputed.

Finally the dancers were taken to a mountaintop shrine to pray for forgiveness. In early September the fits began to fade.

The city wanted to end the suffering.
The treatment it chose only fed the fire.