20 Frightening Cases of Mass Hysteria Throughout History

During the summer of 1518, a woman named Frau Troffea began dancing uncontrollably in the streets of Strasbourg; within a month, no fewer than 400 people had joined what would become one of the most baffling episodes of mass hysteria in history. The dancers reportedly could not stop, continuing to dance for days on end until their feet bled; some are said to have died of exhaustion or heart failure before the epidemic finally came to an end.

Few events in American history have been the subject of as much study as the Salem witch trials of 1692, when, in the village of Salem, Massachusetts, a group of young girls began suffering from fits, hallucinations, and convulsions that they attributed to witchcraft. In the months that followed, more than 200 people were accused of practicing witchcraft, and 20 were executed before the hysteria finally subsided.

In January 1962, three students at a boarding school in Kashasha, Tanganyika, began laughing uncontrollably, and this phenomenon quickly spread to hundreds of students at several schools over the following months. These episodes lasted from a few minutes to several hours and were often accompanied by crying, fainting, and aggressive behavior. This phenomenon caused such disruption that several schools were forced to close.

In 1962, workers at a textile factory in North Carolina eventually became convinced that a mysterious insect in a shipment of fabric was biting them and causing skin rashes, nausea, and dizziness—symptoms that spread throughout the factory within a matter of days. Investigators found no trace of any insect capable of causing these symptoms, and medical examinations revealed no physical cause for the illness affecting dozens of employees. Sociologists who studied the incident concluded that it was a textbook case of mass psychogenic illness, with workplace anxiety and social contagion contributing to the rapid spread of the reported symptoms.

Residents of Mattoon, Illinois, were gripped by panic in September 1944 when reports surfaced of a mysterious prowler who, at night, sprayed a sweet-smelling toxic gas through the windows of homes, causing nausea, paralysis, and vomiting throughout the town. The local newspaper ran a dramatic front-page story about what it called the “mad gasman,” and within a few days, new reports poured in from all over the town. Investigators, however, found no trace of the gas or the perpetrator.

In April 1983, hundreds of Palestinian schoolgirls in the West Bank began collapsing, complaining of dizziness, nausea, and difficulty breathing, in what at first appeared to be a deliberate poisoning. Authorities, government officials, and international health organizations all conducted investigations, but no toxic substance was ever identified, and the outbreak was ultimately classified as a mass psychogenic illness.

When a Pokémon episode featuring rapidly flashing red and blue lights aired in Japan on December 16, 1997, it triggered epileptic seizures in approximately 685 children, who were immediately rushed to hospitals across the country. In the days that followed, thousands more children reported symptoms such as headaches, nausea, and blurred vision, even after the episode had been pulled from the schedule, although many of these subsequent cases had no neurological basis.

A wave of panic swept through Singapore in 1967 after hundreds of men began to believe that their genitals were shrinking and would eventually retract completely into their bodies, a belief that led to numerous attempts to halt this process using pliers, string, and other makeshift devices. This outbreak was attributed to a rumor that pork from animals vaccinated against swine fever could cause this condition, and it spread rapidly before health authorities intervened to reassure the public. Although koro has appeared in various cultures throughout history, the 1967 outbreak in Singapore remains one of the largest and best-documented epidemics ever recorded.

In 2006, students across Portugal began reporting skin rashes, dizziness, and breathing difficulties, convinced that a mysterious illness was spreading through their schools. Investigators attributed this panic to a television series popular among teenagers titled “Morangos com Açúcar” (Strawberries with Sugar), in which a fictional virus had spread through a school; the students appeared to be replicating the symptoms they had seen on screen. Portuguese health authorities confirmed that there was no real virus and classified this outbreak as a mass psychogenic illness directly triggered by fictional media content, making it one of the most unusual cases in recent history.

In November 1938, the city of Halifax, England, was gripped by panic after residents began reporting that a mysterious assailant, armed with a razor blade or a mallet, was attacking his victims on the streets at night. The case drew investigators from Scotland Yard and received nationwide media coverage, plunging the community into a state of fear and isolation; however, it later turned out that the alleged victims had inflicted their own injuries in order to obtain compensation or elicit sympathy.

More than a dozen teenage girls at a high school in Le Roy, New York, began exhibiting symptoms similar to those of Tourette syndrome between 2011 and 2012, including facial tics, uncontrolled spasms, and verbal outbursts that left doctors, parents, and investigators puzzled. Thorough environmental analyses revealed no toxic causes, and neurologists ultimately diagnosed most of the students with a conversion disorder, a condition in which psychological stress manifests as genuine physical and neurological symptoms. 

In the spring of 1954, tiny pinholes and holes began to appear on car windshields in Seattle, and residents were quick to attribute this mysterious damage to all sorts of causes, ranging from radioactive fallout to sand flea eggs to cosmic rays. Reports spread northward across Washington State as local media coverage intensified; most people reporting damage had simply never examined their windshields closely before and were noticing preexisting marks for the first time. Scientists who studied this episode concluded that collective suggestion, combined with a media-induced shift in public attention, had imbued otherwise mundane observations with a deeply alarming significance.

On October 13, 1917, tens of thousands of people gathered in Fátima, Portugal, after three young children claimed that the Virgin Mary had promised a miracle would occur on that day. The crowd, estimated at between 30,000 and 100,000 people, reported seeing the sun spin on its axis, change color, and appear to plunge toward Earth. Researchers who have studied this event have proposed various explanations, including atmospheric optical illusions, retinal distortion caused by staring directly at the sun, and a mass suggestion fueled by the intensity of collective anticipation. This episode holds deep religious significance for many Catholics and is also one of the most frequently cited case studies in academic literature on shared perception and the power of collective expectation.

In the 15th and 16th centuries, several European convents were the scene of unusual collective behavior; one of the best-known accounts describes a French convent where the nuns began meowing in unison like cats for hours each day, until soldiers were stationed outside to put a stop to it. Similar outbreaks were reported in convents across Germany, the Netherlands, and Italy, with reported symptoms including biting, speaking in tongues, animal-like cries, and convulsions—all of which were generally attributed to demonic possession at the time.

Panic gripped New Delhi in May 2001 after dozens of residents reported being attacked at night by a mysterious creature described as a monkey-like figure with metal claws, glowing red eyes, and the ability to leap several stories high. These accounts quickly spread through working-class neighborhoods, causing sleepless nights throughout the city and prompting crowds to chase and attack people mistaken for the creature in the darkness. Extensive police investigations, however, revealed no evidence of the creature’s existence.

Throughout the 19th century, rural communities in New England responded to tuberculosis epidemics by believing that deceased family members rose from their graves to drain the living of their vitality, leading to the exhumation of bodies and the ritual destruction of internal organs to prevent the disease from spreading further. Panic was particularly widespread in Rhode Island and Vermont; one of the best-documented cases was the 1892 exhumation of Mercy Brown, whose organs were burned and whose ashes were dissolved in a liquid that her dying brother was forced to drink. 

In June 1999, a health alert was issued in Belgium after schoolchildren across the country began complaining of nausea, headaches, and dizziness following the consumption of Coca-Cola products, leading to the recall of millions of cans and bottles in Belgium, France, Luxembourg, and the Netherlands. Health investigators found only minor quality issues in a small batch of products; the contamination identified was far too insignificant to explain the scale of the symptoms reported in several regions.

When Gloria Ramirez was admitted to Riverside General Hospital in California in February 1994 with severe heart complications, several members of the emergency room staff who were treating her began to faint, have difficulty breathing, and report an unusual odor, plunging the emergency room into utter chaos. Investigators later hypothesized that Ms. Ramirez had self-administered dimethyl sulfoxide, which may have broken down into a toxic compound in her blood; however, no definitive explanation has ever been confirmed. This case remains one of the most controversial incidents in American medical history, with many researchers asserting that the staff’s symptoms were at least partly the result of a psychogenic illness that spread through the room after the first fainting episodes.

On July 13, 1980, approximately 300 children fainted during a marching band competition held at the Hollinwell Showground in Nottinghamshire, England. They exhibited symptoms such as dizziness, vomiting, and loss of consciousness, an event that made the front pages of national newspapers overnight. No toxic substances, contaminated food sources, or environmental hazards were ever identified, despite extensive testing of the air, water, and soil at the site.

In 1892, a strange epidemic broke out among schoolchildren in Groß Tinz, Germany, when a 10-year-old girl began to suffer from an uncontrollable tremor in her right hand, which was particularly noticeable when she tried to write. The symptoms quickly spread to other students, with some children experiencing generalized seizures, impaired consciousness, and memory loss; a similar outbreak then occurred in Basel, Switzerland, where it even resurfaced several years later.