An Unstoppable Dance
In July 1518, a woman identified as Frau Troffea stepped into a narrow, cobbled street in Strasbourg and began to dance. There was no music. She simply twisted and shook, unable to stop. For nearly a week, she danced almost continuously, until she collapsed from exhaustion. After brief rests, she would rise and begin her frenzied movements again.
Within a week, more than 30 other people had joined her, seemingly against their will. By August, the number of dancers had swelled to around 400. Historical records from the city council, church sermons, and physicians' notes all document the bizarre event. The victims' movements were described as spasming convulsions. Their arms thrashed, their feet became swollen and bloody, and they cried out for help.
Perplexed, city officials consulted local physicians, who ruled out supernatural causes. Their diagnosis was "hot blood," a condition supposedly caused by an overheated brain. Their prescribed cure was not rest, but more dancing. Authorities cleared out guildhalls for the dancers, constructed a wooden stage, and even hired musicians to keep the afflicted moving. This strategy failed. At the plague's peak, as many as 15 people died each day from strokes, heart attacks, and sheer exhaustion. The mania finally subsided in September, after the remaining dancers were taken to a shrine dedicated to Saint Vitus to pray.
Searching for a Cause
Modern science has two primary explanations for the dancing plague, though neither is definitive. One theory suggests ergotism, or poisoning from a fungus called Claviceps purpurea. This mold grows on damp rye and produces alkaloids with effects similar to LSD, causing hallucinations and violent muscle spasms. This hypothesis has weaknesses. Ergot poisoning typically constricts blood flow, which would make coordinated, days-long dancing physically improbable. Also, it is unlikely that so many people would react to the toxin in the exact same way.
The more widely accepted explanation is mass psychogenic illness, formerly known as mass hysteria. The social environment of Strasbourg in 1518 was exceptionally stressful. A series of famines, floods, and diseases like smallpox and syphilis had devastated the population. This intense, prolonged psychological distress may have triggered a collective dissociative state. The belief in Saint Vitus, a saint who could inflict a dancing curse on sinners, was a specific cultural outlet for this widespread anxiety. For a population under extreme duress, this shared belief could have manifested as a physical, contagious compulsion.