What happened
In the middle of July 1518, in the free imperial city of Strasbourg on the Rhine, a woman whom the chronicles call Frau Troffea stepped into the street and began to dance. There was no music and no celebration. She kept going, with short pauses to sleep, for something between four and six days, ignoring her husband’s pleas. Within a week more than thirty people had joined her, and by the end of August one family chronicle put the number at about 400.
The accounts describe people dancing until their feet bled, collapsing from exhaustion and getting up to continue, and some of them dying. The later claim that as many as fifteen dancers a day were dying at the peak is repeated in many retellings, but it does not come from the city’s own records, which say nothing about deaths. What is certain is that the city government treated the outbreak as an emergency and that it lasted, in some form, into early September.
The investigation
Strasbourg’s governing council consulted its physicians. Working within the medical thinking of the day, they ruled out astrological and supernatural causes and diagnosed a natural disease arising from overheated blood. Instead of bleeding the patients, they recommended that the dancers be allowed to dance the fever out. The council accordingly cleared two guild halls and the grain market, had a wooden stage built at the horse market, and paid musicians and strong men to keep the afflicted moving and upright.
The policy failed. Public performance seems to have drawn more people in, and many onlookers read the spectacle as the work of Saint Vitus, whose curse was widely believed to be an uncontrollable dance. The council reversed itself, dismantled the stages, and banned public music and dancing until September, exempting only stringed instruments at private weddings. The worst cases were carted to the saint’s shrine at Saverne, west of the city, where priests put red shoes marked with crosses on their feet, sprinkled them with holy water and recited prayers over them. Shortly afterward the dancing stopped. The sources for all this are the council’s own orders, the city chronicles and the writings of the physician Paracelsus, who visited eight years later and dismissed much of it as deliberate pretending.
The explanations
Two modern explanations compete. The older one blames ergot, a fungus that grows on damp rye and produces compounds related to LSD; outbreaks of ergotism were a real feature of medieval Europe and can cause convulsions and hallucinations. The historian John Waller, whose 2008 book and his 2009 article in The Lancet are the standard modern treatments, rejects this. Ergot poisoning constricts the blood vessels of the limbs and leaves its victims unable to coordinate movement, let alone dance for days, and the dancing plagues cluster along the Rhine and Moselle in a way that does not follow the rye harvest.
Waller’s alternative is a stress-induced mass psychogenic illness. The years before 1518 had brought famine, bitter cold, failed harvests, smallpox and syphilis to Alsace, and bread prices in Strasbourg stood at a generation’s high. In a population that already believed Saint Vitus could inflict compulsive dancing, he argues, extreme distress tipped susceptible people into a dissociative trance in which the expected symptom appeared, and the sight of dancers in public spaces spread it by suggestion. He points to a chain of earlier outbreaks, including one that followed a Rhine flood in 1374, and to modern episodes of psychogenic illness in schools and factories. Other historians, including H. C. Erik Midelfort, caution that sixteenth-century categories of madness do not map neatly onto modern diagnoses, and that the chroniclers’ numbers should be read with care.
Where it stands
That hundreds of people in Strasbourg danced compulsively for weeks in the summer of 1518 is well documented. How many died is not known, and the figure of dozens of deaths rests on later chroniclers rather than the city’s records. The psychogenic explanation is the one most historians now accept, but it remains an inference from circumstances rather than something that can be proved five centuries later, and the episode is still listed among the unsolved puzzles of public health.