In July 1518, a woman stepped into a street in Strasbourg and began to dance. She did not stop for days. Within a month, hundreds of people were reportedly doing the same, and some were said to have died of exhaustion. The Dancing Plague is one of history’s strangest episodes, and it is far from the only one. Across centuries and continents, groups of people have laughed uncontrollably, fainted en masse, developed tics, or become convinced they were under attack, with no shared physical cause that investigators could find.
Historians and psychologists have argued for decades about what really happened in these cases. This article walks through the best-documented events, lays out a timeline, and compares the competing scientific explanations.
What Is Mass Hysteria?
“Mass hysteria” is the popular term. Researchers now prefer mass psychogenic illness (MPI) or mass sociogenic illness. These terms describe the rapid spread of physical symptoms through a group when no environmental or infectious cause can be found, and when the symptoms appear to be driven by stress, belief, and social influence.
The older word “hysteria” comes from the Greek word for womb and carries a long, sexist history, since for centuries doctors dismissed women’s suffering as a uterine disorder. That is one reason modern researchers avoid it. The symptoms in these outbreaks are real. People genuinely cannot stop dancing, laughing, or twitching, and the term “psychogenic” does not mean they are faking.
Psychiatrist Simon Wessely and later researchers such as Robert Bartholomew have described two broad patterns:
- Mass anxiety hysteria: Symptoms like dizziness, nausea, headaches, and fainting spread quickly through a group, usually triggered by a perceived threat such as a strange smell or a rumor of poisoning. Outbreaks tend to burn out within days.
- Mass motor hysteria: Involuntary movements such as dancing, shaking, laughing, or tics spread slowly, often among people under long-term stress, and can last weeks or months.
The Dancing Plague belongs to the second type. Many of the cases below belong to the first.
The Dancing Plague of 1518
The event began in Strasbourg, then part of the Holy Roman Empire. According to surviving records, including city council minutes, chronicles, and physicians’ notes, a woman referred to as Frau Troffea began dancing in a street in July 1518. She reportedly danced for days. Within a week, dozens of others had joined her, and by some accounts the number reached around 400 within a month.
The authorities’ response is part of what makes the case so interesting. Believing the problem was “hot blood” that needed to be danced out, they did not forbid the dancing. They opened guildhalls, built a wooden stage, and hired musicians and strong men to keep dancers on their feet. It made things worse. When the outbreak kept growing, officials reversed course, banned public music and dancing, and sent afflicted people to a shrine of St. Vitus in nearby Saverne, where they performed rituals involving red shoes and a priest’s blessing. The outbreak then faded.
How many people died is uncertain. A frequently repeated claim that dozens were dying each day is not supported well by the evidence, and historian John Waller, who examined the sources closely in his book A Time to Dance, a Time to Die, considers a handful of deaths more plausible than hundreds. Dancing for days could have caused heart attacks, strokes, or exhaustion in vulnerable people, but the numbers are probably inflated by later retellings.
Strasbourg was not unique. Similar “dancing manias” were reported along the Rhine in 1374, with groups gathering in towns such as Aachen, dancing, shouting, and sometimes claiming visions. These episodes show a pattern. They tended to appear in times of hardship and in a culture that already had a script for the behavior.
Other Famous Cases of Mass Hysteria
Tarantism in Southern Italy (15th to 20th centuries)
For centuries, people in the Apulia region of southern Italy believed that the bite of a spider, the so-called tarantula, caused a state of frenzy that could only be cured by dancing, which gave rise to the tarantella. Anthropologist Ernesto de Martino studied the phenomenon in the 1950s and argued that many “bites” were symbolic. The ritual gave people, especially women facing poverty, social pressure, and trauma, a culturally approved way to express distress. In this reading, the spider was less a cause than a story that organized the suffering.
The Salem Witch Trials (1692)
In Salem Village, Massachusetts, several girls began suffering fits, contortions, and trances, and accused neighbors of witchcraft. The crisis ended with roughly 200 people accused and 19 hanged, with others dying in jail. Explanations have ranged from ergot poisoning to conversion disorder, but most historians stress that fear, religious belief, village feuds, and frontier anxiety fueled the escalation as much as any single medical cause.
The Mad Gasser of Mattoon (1944)
In September 1944, residents of Mattoon, Illinois reported that a mysterious figure was sneaking around homes and spraying a gas that caused nausea, paralysis of the legs, and vomiting. Local newspapers amplified the story and police investigated, but no gas, suspect, or physical evidence was found. Sociologist Donald Johnson analyzed the case in 1945 and concluded that suggestion and media coverage played a central role.
The Seattle Windshield Pitting Epidemic (1954)
In the spring of 1954, drivers in Washington State reported tiny pits in their car windshields. The reports spread south from Bellingham to Seattle, and fears turned to radioactive fallout from nuclear tests and other exotic causes. Officials took the issue seriously enough to seek outside help. Investigators found that the pitting was ordinary wear and tear that drivers had never noticed. Once people began looking at their windshields instead of through them, they found damage everywhere.
The Tanganyika Laughter Epidemic (1962)
In January 1962, at a girls’ boarding school in Kashasha, in what is now Tanzania, a few students began laughing uncontrollably. Of about 159 students, roughly 95 were affected, and the school closed in March. The laughter spread to nearby villages and other schools, eventually affecting around a thousand people over many months. Doctors who investigated found no infectious or toxic cause. The episode took place amid the stress of a newly independent nation and the strict pressures of school life.
Koro Epidemics (Singapore 1967, China 1980s)
Koro is a culture-bound syndrome in which a person believes their genitals are shrinking into the body and will cause death. In 1967, rumors in Singapore that eating pork from vaccinated pigs could trigger it led to hundreds of reported cases and a flood of hospital visits. Health officials responded with public education campaigns, and the outbreak ended. Similar epidemics were reported in southern China in the 1980s.
Modern Cases: Le Roy and Social Media Tics (2011 to 2020s)
In 2011 and 2012, a group of teenagers, mostly girls, in Le Roy, New York developed sudden tics and verbal outbursts resembling Tourette syndrome. Environmental causes, including an old chemical spill, were investigated and ruled out by most experts, and neurologists diagnosed functional neurological disorder (also called conversion disorder). In 2020 and 2021, clinicians reported a surge of teens developing tic-like movements after heavy exposure to social media videos featuring people with Tourette syndrome. These cases suggest that the internet can serve as a modern channel for symptom contagion.
Timeline of Notable Mass Hysteria Events
| Year | Event | Location | Type |
|---|---|---|---|
| 1374 | Dancing mania along the Rhine | Aachen and surrounding regions | Motor |
| 1518 | The Dancing Plague | Strasbourg | Motor |
| 15th to 17th c. | Tarantism | Southern Italy | Ritualized, culture-bound |
| 1692 | Salem afflictions and witch trials | Massachusetts | Mixed, with social conflict |
| 1938 | War of the Worlds broadcast (panic often exaggerated) | United States | Media-driven, largely myth |
| 1944 | Mad Gasser of Mattoon | Illinois | Anxiety |
| 1954 | Windshield pitting epidemic | Washington State | Anxiety, perceptual |
| 1962 | Tanganyika laughter epidemic | Tanzania | Motor |
| 1967 | Koro epidemic | Singapore | Culture-bound anxiety |
| 2011 to 2012 | Le Roy tics | New York | Motor, functional |
| 2020s | Social media tic-like behaviors | Global | Motor, online contagion |
The 1938 broadcast is worth noting for a different reason. Newspapers at the time reported widespread panic after Orson Welles’ radio adaptation, but later scholars have argued the scale was greatly exaggerated. It is a reminder that stories about hysteria can themselves spread, and that the press sometimes manufactures the mass panic it reports.
The Competing Scientific Explanations
No single theory explains every case, and for the oldest events we may never know. Here are the main contenders.
1. Ergot Poisoning
Ergot is a fungus that grows on rye and other grains. Eating contaminated bread can cause convulsive ergotism, with spasms, hallucinations, and a burning sensation in the limbs. The theory was applied to both the Dancing Plague and Salem (a 1976 paper in Science by Linnda Caporael popularized the Salem link).
The problem: Ergotism also constricts blood vessels, which causes painful gangrene and would make days of coordinated dancing physically impossible. Critics also point out that the poisoning would have hit whole households, not isolated individuals. The Salem argument drew an immediate rebuttal in the same journal. Most specialists now consider ergot an unlikely explanation for the Strasbourg events.
2. Psychogenic Illness Triggered by Stress
This is the leading view among historians and psychologists. In Strasbourg, the region had suffered famine, high food prices, and outbreaks of diseases like smallpox and syphilis. Many residents also believed in St. Vitus, a saint who could punish sinners by making them dance. Under severe stress and a shared belief, a trance-like state could take hold and spread. Waller supports this view.
Strengths: It fits the evidence of hardship and belief, and it matches modern cases like Tanganyika and Le Roy.
Weaknesses: It is hard to prove for events 500 years old, and critics argue it can become a catch-all label when no other cause is found.
3. Social Contagion and Cultural Scripts
This theory emphasizes that symptoms spread through observation and expectation. People pick up the “script” for how a sufferer behaves, from dancing to fainting to tics, and then unconsciously reproduce it. The nocebo effect, where negative expectations produce real symptoms, is one proposed mechanism. This explains why outbreaks follow local beliefs: dancing in a culture that believes in St. Vitus, spider bites in a culture that believes in tarantism, koro in cultures where the syndrome is already known.
Strengths: It explains the cultural specificity of each outbreak and how the media or rumors can accelerate spread.
Weaknesses: It describes how symptoms spread better than why a given person developed them in the first place.
4. Environmental Toxins and Infection
In many modern outbreaks, the first suspicion is a toxin or pathogen. Sometimes it is right, since carbon monoxide leaks, for instance, genuinely cause group illness. In the cases listed here, though, investigators repeatedly searched for chemicals, bacteria, and viruses and found nothing consistent.
Strengths: It is testable in the present day and should always be ruled out first.
Weaknesses: Where no cause is found, it can leave families and communities feeling dismissed, which is why careful, respectful communication matters.
5. Collective Coping, Protest, or Release
Some researchers see outbreaks as an unconscious response to oppression or powerlessness. Tarantism gave people, especially women, a socially accepted outlet. The Tanganyika school outbreak may reflect the pressure on students. The difficulty with this framework is that it can be unfalsifiable, since almost any society has some tension that can be pointed to after the fact.
How the Explanations Compare
| Explanation | Best fits | Main weakness |
|---|---|---|
| Ergot poisoning | Salem, 1518 (debated) | Cannot explain days of sustained dancing; wrong physical symptoms |
| Stress-driven psychogenic illness | 1518, 1962, 2011 | Hard to verify for old cases |
| Social contagion and cultural scripts | Nearly all cases | Explains spread more than origin |
| Toxins or infection | Some modern outbreaks | Rarely confirmed in the classic cases |
| Collective coping or protest | Tarantism, Tanganyika | Risk of unfalsifiable storytelling |
Most experts now favor a blended view. Stress and vulnerability create the conditions, belief and culture provide the script, and social transmission does the rest.
How Do Researchers Tell Psychogenic Outbreaks From Real Poisonings?
Modern investigators look for several patterns. Psychogenic outbreaks tend to affect more females than males, start with a visible trigger event, spread through lines of sight and social ties rather than through geography, and involve symptoms that are benign but dramatic, such as dizziness, fainting, or headaches. There is often a rumor of a smell or a threat. Crucially, symptoms don’t match the known effects of any toxin, and tests find nothing. Of course, doctors rule out physical causes first, since dismissing a real exposure as “hysteria” has done real harm in the past.
Why These Episodes Still Matter
It is tempting to read the Dancing Plague as a quirk of a superstitious age. But the same mechanisms operate today, and arguably faster. Social media can spread symptoms, rumors, and fear across continents in hours. Understanding mass psychogenic illness helps schools, hospitals, and governments respond better: by ruling out real hazards, avoiding blame, limiting sensational coverage, and treating sufferers with compassion rather than ridicule.
It also challenges a comfortable idea, that the mind and body are separate. These episodes show that belief, stress, and community can produce genuine physical effects. People in Strasbourg were not pretending, and neither were the girls in Tanganyika or the teenagers in Le Roy.
Conclusion
The Dancing Plague of 1518 remains unsolved in the strict sense, because no one can examine the dancers. But the best available evidence points to a combination of extreme hardship, deep religious belief, and social contagion, rather than a poisoned loaf of bread. The same ingredients appear again and again in later outbreaks, from Italian tarantism to the Tanganyika laughter epidemic to online tic contagion.
History’s mass hysteria events remind us that human beings are social creatures to the core. We catch feelings, ideas, and sometimes symptoms from one another, and when the pressure is high enough and the story is believable enough, whole communities can be swept up in something that no single person chose.
Suggested sources to read and link:
- John Waller, A Time to Dance, a Time to Die: The Extraordinary Story of the Dancing Plague of 1518 (2008)
- Robert Bartholomew and Simon Wessely, research on mass psychogenic illness (e.g., “Protean nature of mass sociogenic illness,” British Journal of Psychiatry, 2002)
- Linnda Caporael, “Ergotism: The Satan Loosed in Salem?” Science (1976), and the reply by Spanos and Gottlieb in the same journal
- Donald Johnson, “The ‘Phantom Anesthetist’ of Mattoon,” Journal of Abnormal and Social Psychology (1945)
- Rankin and Philip, report on the Tanganyika laughter epidemic, Central African Journal of Medicine (1963)
