The Summer a City Couldn't Stop Dancing: What Really Happened in Strasbourg in 1518

In July 1518, in the city of Strasbourg, a woman stepped into the street and began to dance. There was no music and no celebration. According to later accounts, her name was Frau Troffea, and she kept going for hours, then days, stopping only when exhaustion overwhelmed her, then starting again.

She was not alone for long. Within a week or so, dozens of other people had joined her. By August, the city's records describe a crisis. Men and women were dancing in the streets and squares, unable or unwilling to stop, their feet bloody, their bodies collapsing. Some contemporary and near-contemporary sources suggest that people died, though how many is impossible to say with confidence.

It sounds like legend. It isn't. The dancing plague of 1518 is one of the better-documented strange events of its era, recorded in notes by physicians, sermons, city council records and chronicles. That documentation has allowed modern historians to piece together what happened, and to make a strong case for why.

What the sources tell us

Strasbourg in 1518 was a prosperous free city of the Holy Roman Empire, today part of France. Its records show that local authorities took the outbreak seriously and tried to understand it. Physicians were consulted. The explanation they offered was rooted in the medicine of the time: the dancing was caused by "hot blood", a natural illness rather than a curse or demonic possession.

Their proposed treatment is the most famous part of the story. If hot blood was the problem, the reasoning went, the afflicted needed to dance it out. The authorities cleared space for the dancers, reportedly using guild halls and setting up a stage in a market. They hired musicians and even arranged for strong men to hold up exhausted dancers and keep them moving.

It was a disaster. Rather than burning out, the outbreak seems to have grown. Music and public attention appear to have drawn more people in. Eventually, the city reversed course. It banned public dancing and music, except for weddings and similar occasions, and only with restrictions. Many of the dancers were taken to a shrine dedicated to St Vitus in the hills near the town of Saverne, where rituals were performed in the hope of a cure. In the following weeks, the outbreak faded.

How many people danced?

Popular retellings often claim that around 400 people were affected and that as many as 15 people a day were dying. Historians are much more cautious. Some later sources give higher numbers, while others mention far fewer. The more reliable records point to dozens of dancers at least, and possibly more, but the most dramatic death tolls are not well supported by contemporary evidence.

That uncertainty is worth keeping in mind. Even sober accounts of the dancing plague have a habit of growing with each retelling. The core of the story, however, is solid: a large group of people in one city danced compulsively for days and weeks, and the authorities struggled to stop it.

The theory that doesn't fit: poisoned bread

One popular explanation blames ergot, a fungus that can grow on rye, especially in damp conditions. Eating contaminated bread can cause ergotism, a serious illness that has been linked to hallucinations, convulsions and gangrene. Ergot contains chemicals related to LSD, which makes the theory sound appealing for an outbreak of strange behaviour.

Many historians are sceptical. Ergot poisoning restricts blood flow and causes painful spasms. It is hard to see how it would allow people to dance in coordinated movements for days at a time. It also doesn't explain why the dancing spread from person to person in a social pattern, or why it was concentrated in one city and one period, rather than appearing wherever contaminated grain was eaten.

The theory that does fit: a mind under pressure

The explanation most widely favoured by historians today is mass psychogenic illness, an older term for which is mass hysteria. In such outbreaks, physical symptoms spread through a group without a physical cause such as infection or poisoning. They are real symptoms, not acting, but they arise from shared stress, fear and belief.

The historian John Waller, who wrote a detailed book about the event called A Time to Dance, a Time to Die, argues that Strasbourg in 1518 had all the ingredients for such an outbreak. The region had suffered years of hardship, including bad harvests, high food prices, disease and widespread poverty. Many people were desperate and frightened.

Crucially, the culture also offered a script. In this part of Europe, there was a widespread belief that St Vitus could punish sinners with a curse that forced them to dance. Believing in such a curse, Waller suggests, made it possible for people under extreme stress to fall into trance-like states in which dancing felt beyond their control. When the city's response put the dancing on public display, accompanied by music, it reinforced the belief that this was a real affliction spreading among the population.

The ending fits too. The cure involved a pilgrimage to a shrine of the very saint believed to have caused the curse. If belief helped to start the outbreak, belief may also have helped to end it.

Not the only dancing epidemic

Strasbourg was not unique. Accounts describe other dancing outbreaks in medieval Europe, including a large one in 1374 that spread through towns along the Rhine and into the Low Countries. These earlier episodes help explain why people in 1518 already had a cultural framework for what was happening to them.

Mass psychogenic illness hasn't disappeared either. A famous modern example began in 1962 at a girls' boarding school in Kashasha, in what is now Tanzania, where uncontrollable laughter spread among pupils and then to surrounding villages, forcing schools to close temporarily. More recent outbreaks have involved fainting, tremors or other symptoms spreading through schools and workplaces. The forms change with the culture. The underlying mechanism, stress meeting shared belief, appears remarkably consistent.

Why it still matters

The dancing plague can seem like a historical curiosity, an oddity to share on social media. But it offers serious lessons. It shows how powerfully stress can shape the body, and how much our symptoms can be influenced by what we expect and believe. It shows how a well-meaning response, in this case hiring musicians, can make a crisis worse by amplifying it.

And it shows how fragile the line between individual and collective behaviour can be. One woman dancing in the street became, within weeks, a city in turmoil. Strasbourg's authorities did what they thought was rational, guided by the best medicine of their day. We have better medicine now. Whether we are always better at recognising when fear itself is spreading is a much harder question.