We as a species seem to be prone to feeding off of those around us and exhibiting shared behaviors that apparently have the potential to spread through our ranks to infect us like some insidious disease. In numerous cases throughout history there have been times when it looks as if phantom illnesses, mass hallucinations, and unusual behaviors have manifested amongst a large number of people at the same time, simultaneously showing us how little we know of the human mind and illustrating that there are some mysteries of our consciousness that we are nowhere near being able to explain. In cases such as these strange phenomena have spread out and affected entire communities and populations, and it has come to fall under the umbrella term “mass hysteria.” Variously blamed over the ages on demons, ghosts, witchcraft, possession, and insanity, mass hysteria is a phenomenon that is still little understood, and here are some of the more bizarre cases of it.

A very weird case of mass hysteria originates from the year 1844, when a J. F. C. Hecker gave in his book Epidemics of the Middle Ages an account of a strange series of events that gripped a secluded convent of nuns in France in the 15th century. According to the story, one day one of the nuns began to suddenly and inexplicably meow like a cat rather than speaking. This was a bit ominous, because in this particular region at the time cats were thought to be servants of the Devil, but things grew odder still when other nuns at the convent began to restlessly meow as well, until there were around a dozen of them doing this in unison at certain hours of the day, sometimes for several continuous hours without stopping. It got so bad that soldiers were apparently called in to stop the strange phenomenon with force, of which was written:

The whole surrounding Christian neighborhood heard, with equal chagrin and astonishment, this daily cat-concert, which did not cease until all the nuns were informed that a company of soldiers were placed by the police before the entrance of the convent, and that they were provided with rods, and would continue whipping them until they promised not to meow any more.

At the time this outbreak of meowing was blamed on sinister demonic possession, but it is unclear what really caused it. Medieval convents seem to have actually been quite prone to such phenomena, as there was another very unusual case from 15th century Germany, in which nuns in one convent started to gain the unsettling habit of lashing out to bite those around them. Apparently other convents began to experience the same outlandish incidents, with nuns savagely biting or even clawing at each other for no discernible reason whatsoever, and it was a perplexing and not a bit spooky mystery that was also at the time blamed on demons. The case of the biting nuns was written of by the psychologist John Waller for The British Psychological Society, and no clear reason for this weird behavior has ever been discovered.

Animalistic behavior was also recorded in 1676, when orphans living at a school in Hoorn, Holland spontaneously started behaving like feral dogs. Kids around the orphanage suddenly and without warning reportedly began to go into a trance, after which they would emerge to lope about on all fours, bark, growl, snarl, and bite. One theologian named Balthasar Bekker claimed to have seen this phenomenon first hand, and wrote of it thus:

They tugged and tore themselves, striking at the ground with their legs and arms end even with their heads, crying yelling and barking like dogs so that it was a terrifying thing to see.

As with the cases of the mysterious convents, this was all blamed on the work of the Devil, and the whole town prayed for the children and exorcisms were carried out until the anomalous affliction finally subsided. As with the meowing and biting nuns, the mystery of the dog-like orphans and their disturbing behavior has never been satisfactorily solved, although it is now thought to be a case of mass hysteria of some sort.

It seems to be a trend for cases of mass hysteria to feature startlingly aberrant behavior in some form or another, and one of the more well known cases of mysterious mass hysteria is that of a plague of dancing that overcame far-flung rural areas of Medieval Europe from between the 13th and 17th centuries. The condition, which would variously be called Choreomania, Dancing Mania, the Dancing Plague, St. John’s Dance, or the Dance of St. Vitus, typically involved people, sometimes whole mobs of them, abruptly getting up to jump, jig, jerk, hop, and dance about for no reason as if to music that only they could hear. In most cases it was very clear that the victims were not merely mindlessly and spasmodically convulsing, but are rather actually purposefully carrying out certain dance patterns with their arms, bodies, and legs.

One early account of the phenomenon occurred in July of 1374, in Aachen, Germany, when people from over a dozen separate villages along the Rhine River began to dance about uncontrollably in the streets, and this would spread until thousands of people were allegedly overcome by the throes of dancing mania. These unfortunate people would often continue to flail about and dance about wildly for hours or even days on end before finally dropping from exhaustion or even dying from heart attacks or strokes. In some cases collapsing from exhaustion didn’t even stop people from their unnatural desire to keep dancing, with many still rhythmically convulsing and jerking about even after they had crumpled to the ground.

Another outbreak of the Dancing Plague hit Strasbourg, France in 1518. It all started when a woman called Frau Troffea was overcome with the uncontrollable desire to start wildly dancing, which she would do for several days straight without eating or sleeping. Oddly enough, as she did her hypnotic dance though the streets other people became infected by the urge to dance as well, until hundreds of people were in thrall to the bizarre affliction. As the crowds of mysteriously dancing people grew it was decided that the behavior was a symptom of some strange fever, perhaps even a curse, and that the afflicted had to allow it to run its course. The unaffected townsfolk reportedly even went about helping those who were under the spell, erecting stages for them to dance upon and even bringing in music and other dancers to join them. This did little good, and people continued to drop from exhaustion or even die.

The 1518 plague of dancing was supposedly not brought to an end until the affected were finally deemed to be possessed and forced to pray to Saint John and Saint Vitus, which purportedly freed them from the supposed curse. Other similar outbreaks of Dancing Plague would emerge all over Europe in places such as Italy, Luxembourg, France, Germany, Holland, and Switzerland, until in the 17th century the phenomenon just stopped as suddenly as it had arisen, leaving mystery hanging over the whole thing. Theories as to what caused it include mass poisoning, stress induced hysteria, psychosis, and ergot poisoning, which is caused by a grain fungus and can produce hallucinations and bizarre behavior, but the true reason remains a mystery and the Dancing Plague continues to be a puzzling historical oddity to this day.

Interestingly, there was an odd case that seems very similar to the Dancing Plague that happened in 1939 at a high school in the U.S. state of Louisiana. In this case, a student was suddenly overcome by a fierce twitching of the leg, gradually evolving to the point where she almost seemed to be twitching and convulsing her legs to some unheard music. Other students also began to do this, claiming that they could not control it, as if something were taking over their body. So many students began to demonstrate this twitching that scared parents reportedly were pulling their kids out of school so that they wouldn’t catch it, but the whole incident would suddenly stop a week later, leaving no answer at all as to why these kids had been twitching against their will.

In later years we have a very odd case from Kashasha, in Tanzania, Africa, where in 1962 a boarding school for girls was overcome by an unexplained bout of mass hysteria of some form that has never been explained. Three girls at the school reportedly suddenly began to laugh hysterically and uncontrollably one day for no apparent reason, and this soon spread to other girls until much of the school was in a constant fit of laughter. These young girls would apparently laugh for hours or even days non stop, with no clear way to stop it and no discernible catalyst.

The epidemic of laughter did not stop even with the eventual closure of the school from whence it first originated, as neighboring communities, villages, and schools soon had the same problem on their hands as students for no reason began breaking down into fits of abrasive, hyena-like laughing that would not abate. At one point it was estimated that over 1,000 young people were in the throes of the strange phenomenon, often accompanied by symptoms such as pain, fainting, respiratory problems, rashes, and fits of crying, forcing school closures and emergency measures far and wide. Then, around 18 months after it started the laughing abruptly stopped for no apparent reason. No medical reason for what has become known as the Tanganyika Laughter Epidemic has ever been found.

In addition to bouts of collective odd behavior, there is a sort of subspecies of this mass hysteria phenomenon that involves the populace conjuring up some sort of phantom enemy or spectral, evil presence amongst them. An early example of this comes from all the way back in 1630, when the residents of Milan, Italy became convinced that a shadowy entity was trying to actively poison them. Many of the locals became convinced that a mass poisoning was at hand, possibly from the Devil himself, and there were numerous reports of doors or entryways marked with “a curious daub, or spot,” which was thought to be a sure sign of being targeted for extermination.

Things got so out of hand that authorities were having people executed, with even the slightest suspicious behavior seen as trying to spread the awaited poison apocalypse, such as an elderly man who was set upon by an angry mob for merely wiping down a stool. It got to the point that to be out on the streets at night was a sure sign of guilt. More and more people were arrested and subsequently tortured, during which time some of them confessed to being in league with the Devil and in on a conspiracy to poison everybody. On many occasions these people would name accomplices, who would also be tortured or executed, and things got quite out of hand indeed, even though there was not a shred of evidence that anyone had actually been poisoned. The whole thing finally passed, with no mass poisoning in sight and the only ones dead those who had been executed for their part in a nonexistent conspiracy.

Another well-known example of this is a case from the 1930s, when across the U.S. states of Virginia and Illinois there came reports of a phantom attacker lurking outside of homes and spraying the people within with poison gas. What came to be known as the “Mad Gasser” was accused of knocking mostly young women out with a mysterious gas, and this gas was claimed to cause effects such as nausea, vomiting, and burning sensations in their mouths and throats. However, despite numerous investigations by police there was never any evidence of such a substance or attacker. Was this all mass hysteria or was there more to this?

In 1962 the mysterious enemy conjured up was not a person at all, but an enigmatic insect that was said to roam about a textile factory in the United States. Workers began to complain that they had been bit by the bug, after which they fell down with various flu-like symptoms including numbness, nausea, dizziness, and vomiting. Cases of the mysterious illness spread like wildfire through the factory, with many of these victims hospitalized, but doctors could never find anything actually physically wrong with them and no sign that any bug had bit them as described. Indeed, the symptoms reported were inconsistent with those of any known spider or insect bite in the first place, leaving a bizarre mystery that couldn’t be explained. The US Public Health Service Communicable Disease Center would eventually conclude that it was all the result of a bizarre mass hysteria.

Even more recently, in 2002 there was a case from Uttar Pradesh, in India, where locals became convinced that there was an alien entity going around attacking people by burning them with some sort of laser weapon or flat-out attacking with its claws. What would came to be known as the Muhnochawa, or “Face-Scratcher was blamed for the deaths of at least 7 people, and authorities somehow made the panic even worse by claiming that it was all the result of a genetically engineered insect weapon. This official pronouncement did not make things better at all, inciting riots in the streets, with some even reportedly committing suicide to be spared from the invasion, be it foreign or from another world. Interestingly, throughout all of this there were numerous witnesses who came forward with injuries and burn marks they claim had been inflicted on them by these phantom enemies. The government would later sweep it all under the carpet and write it all off as mass hysteria, with the injuries self-inflicted.

How did these cases of mass, shared delusions come about? Are these phenomena rooted in socio-cultural pressures, stresses, and psychological mysteries? How can we explain these bizarre occurrences in a way that fits in with what we know of the world and the human psyche? As much as we strive for answers to such riddles it seems that the human condition is a complicated one, and there are mazes within mazes that delve down into areas beyond our current understanding. Maybe someday we will know the answers we seek.