On Saint John the Baptist’s Day, Friday, 24 June 1374, a crowd had gathered in the marketplace of Aachen in the Holy Roman Empire to watch the annual religious procession that marked the feast. The procession had not gone well. The Rhine flooding of the previous spring had inundated farmland for forty kilometers downstream and had been followed by a poor wheat harvest. The plague had passed through Aachen for the third time in twenty-six years, killing roughly one in five of the city’s residents. The flagellant penitential movement, which had appeared during the Black Death of 1349 and had been formally condemned by Pope Clement VI, had been quietly reviving in the Rhine valley for the past two years. The 1374 Saint John’s Day procession was therefore a more anxious and theologically loaded event than usual.
At some point during the procession — the surviving chronicle accounts disagree on the exact moment — a small group of pilgrims at the rear of the procession began to dance. They moved out of the orderly procession line. They formed a loose ring at the edge of the marketplace. They danced. Within the next hour, perhaps several dozen other pilgrims and bystanders joined them. By the end of the afternoon, several hundred people in the Aachen marketplace were dancing — without coordination, without music, in many cases without recognition of anyone they knew, occasionally collapsing from exhaustion only to rise after a few minutes and continue.
The dancing did not stop that night. It continued through the following day. Over the next two weeks, it spread westward into the Low Countries — to Maastricht, to Tongeren, to Utrecht, to Liège, to Cologne — and persisted at varying levels of intensity through the autumn of 1374 and into the winter. Some affected individuals danced for hours and then resumed normal life; some danced for days; some died of exhaustion or heart failure during episodes. The total number of people affected has been estimated by modern historians at several thousand, with a peak intensity in the September-October 1374 window. The peak number of simultaneous dancers in any one location was probably in the range of one to two thousand, in Liège or Cologne, in the late summer.
The 1374 Aachen mania was substantially larger and longer-lasting than the more famous 1518 Strasbourg episode and is in most respects the largest documented mass-dancing event in European history. It is also, despite its scale, almost entirely forgotten outside specialist medical-history scholarship.
What the chronicles describe
The principal contemporary source is the Chronicon of the Augustinian friar Peter of Herental, who lived in the Brabantine monastery of Floreffe and was writing in the late 1370s — within five years of the events he describes. Peter’s chronicle records the Aachen events in some detail and connects them to subsequent outbreaks in the Low Countries. He gives a description of the affected dancers that is striking in its specificity:
“The dancers afflicted by this malady would jump up and down, neither hearing nor seeing those around them. They would call out the names of demons. Many among them were seen to have their bellies grossly swollen. They would dance without rest until they fell down dead, or until they were tightly bound with cloths. Some of the dancers, after recovering, said they had felt themselves to be in great water, and to be drowning.”
The description has several features that the medical-history literature has analyzed extensively. The reference to “bellies grossly swollen” probably indicates that some affected individuals were exhibiting signs of physical exhaustion, hyperventilation, or — possibly — the abdominal symptoms of an underlying poisoning. The “great water” memory reported by some survivors is consistent with a dissociative or trance state of the kind seen in modern cases of mass psychogenic illness. The reference to dancers “calling out the names of demons” is consistent with the period’s interpretive framework — the dancers were assumed to be possessed and were calling out the name of the possessing entity, which the chronicler’s friars then dutifully recorded.
The dancing began on Saint John’s Day, which was significant. The day commemorated Saint John the Baptist, whose iconographic associations included desert visions, prophecy, and a particular Rhineland folk tradition of Sankt-Johannis-Tanz — a celebratory dance, with bonfires, that had been part of the local pre-Christian midsummer festival and had been incorporated into the Christian feast. The line between the celebratory midsummer dance and the involuntary dancing mania was, in 1374, not always clear to the dancers themselves. Some affected individuals reported in subsequent accounts that they had not been certain, in the first hours, whether they were dancing voluntarily or under compulsion.
How it moved
The mania spread along recognizable trade and pilgrimage routes. Aachen sat at the western edge of the Holy Roman Empire near the Low Countries border. The two largest follow-on outbreaks — Liège and Cologne — sat on the next-largest population centers along the same Rhine-Meuse river network. Smaller outbreaks were documented in Utrecht, Tongeren, Maastricht, and several smaller towns of the Brabant. The geography is, in modern epidemiological terms, the geography of a contagion that moves at the speed of human travel.
The mechanism, in the modern medical-history understanding (Waller 2008, Bartholomew 2000), is mass psychogenic illness — MPI — also called culturally bound dissociative epidemic. The basic mechanism is: in a population under acute stress, with a culturally available “script” for involuntary trance behavior, the behavior can spread from person to person through social observation, with individual sufferers entering genuine altered states of consciousness rather than performing voluntary behavior.
The 1374 Rhine-valley population had several acute stressors: post-plague mortality grief still raw twenty-five years later, flood-driven food insecurity, the disruption of the Catholic-Hussite religious tensions that were intensifying across the empire, the influence of the still-active underground flagellant movement preaching apocalyptic theology. The cultural “script” for involuntary trance behavior was the Sankt-Veit-Tanz — the dance of Saint Vitus — a folk-theological category that had been in the Rhineland mental landscape for at least two centuries. The contagion did the rest.
The Bukoba schoolgirl outbreak of the 1962 Tanganyika laughter epidemic operated by the same mechanism, with the cultural script being laughter rather than dance. The 1518 Strasbourg episode operated by the same mechanism. Modern MPI cases — schoolgirl fainting epidemics, factory-worker chemical-smell episodes, military-base illness clusters — all operate by the same mechanism. The 1374 Aachen outbreak was, in this framework, the largest and best-documented historical case in the European record.
What ended it
The mania subsided through the winter of 1374-1375, slowly, in a pattern consistent with the modern understanding of how MPI outbreaks resolve. The Catholic Church’s intervention took two forms. The first was theological — by autumn 1374, the church had formally diagnosed the dancing as the work of a specific demon (named, in some local accounts, Hertvik) and had organized exorcism rites in the affected cities. The second was practical — large numbers of affected individuals were taken on pilgrimage to the shrine of Saint Vitus at the small Saxon monastery of Corvey, several days’ journey east of the Rhine. The pilgrimage was a culturally appropriate “container” for the affliction. People who had been dancing for days returned from Corvey reporting that the dancing had stopped during the pilgrimage and had not resumed.
The recovery rate was, by the available accounts, high. Most affected individuals returned to normal life within a few months. The total number of dead — from exhaustion, from heart failure during episodes, from accidental injury — has been estimated at between fifty and several hundred across the entire Rhine-Meuse region. The total death count was substantially smaller than the contemporary Black Death recurrence in the same population in the same years.
The Aachen authorities, by November 1374, had banned public dancing in the city — a ban that was lifted gradually over the following two years. The Aachen archive’s record of the ordinance survives in the city’s Stadtbuch and notes, drily, that “dancing in the marketplace shall not be permitted, on penalty of fine, until the cause of recent disturbances be better understood.” The cause was never better understood. The ban was simply allowed to expire.
The 1374 episode was not the last. Smaller dancing manias would recur in the Rhineland and the Low Countries at intervals through the following two centuries. Each subsequent outbreak was smaller. The last documented major dancing-mania episode in the region was the 1518 Strasbourg case. After Strasbourg, the dancing manias appeared to have run their cultural course. The cultural script that had made the involuntary trance behavior available across the Rhine valley was disappearing — replaced, in the sixteenth century and after, by other available cultural scripts for similar stress reactions.
The marketplace at Aachen where the 1374 mania began is now the Marktplatz. It is paved with cobblestones from the eighteenth century. A small plaque, installed in 1974 on the 600th anniversary, names the date and gives the brief account. The plaque is in German. Most tourists walk past it without noticing.