In July 1518, a woman named Frau Troffea walked into a street in Strasbourg and started dancing. No music, no apparent reason, and, according to the records of the time, no stopping. She danced for days. Today, historians believe it was an extreme case of mass hysteria. Then others joined her. Within weeks, dozens of residents were dancing non-stop through the city’s streets, and some people actually died of exhaustion, heart attacks or strokes. This isn’t some medieval legend that got exaggerated over the centuries. It’s one of the best-documented episodes in European history, backed by city council records, doctors’ prescriptions and chronicles written at the time.
A city that couldn’t stop dancing
Strasbourg, then part of the Holy Roman Empire, had just come out of a brutal stretch: famine, smallpox, syphilis, and glaring inequality between ordinary people and the clergy or nobility. Into that pressure cooker walked Frau Troffea’s “dance,” which spread through the population like a social contagion. The authorities, far from banning it, did something that looks like a textbook mistake today. They built a wooden stage and hired musicians, convinced that if people danced “enough” they would recover faster. It backfired spectacularly. The music pulled in even more dancers, and the whole thing got worse. At its peak, chronicles describe roughly 400 people dancing at once, many of them collapsing from sheer exhaustion.
Mass hysteria: what was really happening to these people?
For centuries the blame fell on Saint Vitus, a saint believed to curse sinners with uncontrollable dancing. That belief is why many of the afflicted ended up making pilgrimages to chapels dedicated to him, hoping for a cure. Modern historians, though, aren’t satisfied with the religious explanation. Medical historian John Waller, of Michigan State University and author of the definitive book on the episode, argues this was an extreme case of stress-induced mass hysteria. A population worn down by hunger and fear, already deeply convinced of Saint Vitus’s curse, could genuinely slip into a trance-like state just from watching others dance uncontrollably.
The other leading theory is chemical: ergot, a fungus that contaminates grain stored in damp conditions. It produces compounds chemically related to LSD, capable of triggering hallucinations and spasms. It’s a tempting explanation, but Waller pushes back on it with a fairly solid argument. Ergot also restricts blood flow and typically causes gangrene and burning sensations in the hands and feet, symptoms no chronicler from 1518 ever mentions. Someone poisoned by ergot would struggle to stay on their feet dancing for days on end, let alone weeks.
It wasn’t a one-off
Here’s the curious part: Strasbourg wasn’t an isolated case, just the deadliest entry in a string of “dancing plagues,” or choreomania, that kept popping up along the Rhine and Moselle rivers between the 14th and 17th centuries. Most of those episodes fizzled out on their own within days or weeks, but none were as well recorded or as lethal as the 1518 outbreak. It dragged on for over a month before authorities finally dropped the stage and the musicians. They started shipping the afflicted off to mountain chapels dedicated to Saint Vitus instead — where the phenomenon gradually burned itself out.
The consensus among historians today, as outlined by outlets like History.com, is that the 1518 “dancing plague” probably combined several ingredients at once: a genuine subsistence crisis, a widely shared religious belief in one very specific curse, and the almost hypnotic pull of watching a crowd do the exact same thing without stopping. No single ingredient fully explains it on its own. That is exactly what makes this one of history’s strangest cases of mass hysteria, and a reminder of just how far the body will follow the mind when social pressure gets heavy enough.
If you want the full story of how that unstoppable dance actually broke out, we already covered it in detail in our chronicle of the dancing plague that struck Strasbourg.