Today’s tale is set in the city of Strasbourg – then part of the Holy Roman Empire – the date, mid July 1518. Frau Troffea, a local woman for whom there is little description of in the public domain – so I choose to picture her as a medieval Toni Basil – comes waltzing out of her home, down the streets of the city. Dancing to the beat of an unknown drummer, she spun and twisted, thrusting limbs akimbo in what at first seemed a dance of joy…. She shook and pirouetted till she collapsed out of sheer exhaustion. Not done yet, she dusted herself off, and continued to dance the night away – into the next day, and the next – till a week after striding out in public, she found herself joined by 34 other dancers – all moving and a grooving to the same silent reel.
At this point it was clear to all the medieval flash-mob were having anything but a great time. Several dancers screamed for help – others appeared to be zoned out, in a trance.

By the time the great dancing plague of 1518 was done with Strasbourg in mid August, around 400 people had danced themselves to death. The incident remains a matter of conjecture to this day, though medical experts have a pretty clear idea what caused this plague. More on that soon.

Dancing plagues were very much a medieval occurrence, though likely were that era’s manifestation of a mass hysteria incident – something we continue to see to this day in different forms. Strasbourg was one of several such incidents. The earliest accounts come from Christian preachers who were later canonized, and as such carry the usual distortions found in hagiographies. In one tale, from the 7^th century, French Bishop Eligius became so incensed with a group of dancers disturbing the solemnity of the vigil before the feast of St Peter, he cursed the group to dance non-stop for a year. Legend has it, a year to the day these poor dancers gave out -most of them dropping dead of exhaustion. Another legend tells of the missionary Willibrord travelling through Waxweiler, Germany in the 8^th century. He spotted a group of revelers dancing in a graveyard, and sociopathically cursed the group to dance forever. Three days later, he would be back in Waxweiler, where, after some begging and cajoling from the families of the dancers – he cured them of their dance fever.

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On Christmas eve 1021, a large group of parishioners broke into an uncontrolled dance in the town of Bernburg. They continued till exhausted. Another early case involves a large group of children dancing their way from Erfurt, Germany to the neighboring town of Arnstadt – some 20 kilometers away. In 1278 in Maastricht, a group of 200 dancers congregated on a bridge over the river Meuse – dancing till the bridge gave way under them. The dancing plague, however wouldn’t go truly viral till the 1370s, when the phenomenon would occur in dozens of cities across Germany, Eastern France and the Netherlands. Villagers would dance as if in great joy, all the while screaming in pain and begging the clergy to cast the demon out of them.

Back in Strasbourg the authorities tried to make sense of the plague. In trying to come up with an explanation, they discovered Frau Troffea was ordered to do the housework by her husband just prior to breaking into dance. After flat-out refusing to clean the house, she hot-footed it out the house and down the road. Their best guess, based on this evidence, was in the heat of summer the townspeople were suffering from hot bloodedness. They needed to dance the sanguine infection out of their systems if they hoped to recover. The order was given to bring in musicians, and professional dancers from neighboring towns. Stages were built. The doors to the dance halls were thrown wide open. A massive dance party raged on for a month, till everyone was all danced out – and hundreds had died.   

What could have caused such an incident?

In a 2009 article for the Lancet, historian John Waller suggested the dancers had descended into an altered state of mind. Having discounted ergot poisoning – Ergot is a fungus which gets into flour by growing on rye stalks, and can cause hallucinations and involuntary movements – he suggests a psychological cause. Strasbourg had been through a couple of particularly awful years. Recent harvests had been poor, leading to a leap in the cost of grain. The region was wracked with multiple diseases at the time also, from bubonic plague to leprosy to an outbreak of syphilis. Surrounded by doom and gloom, the town’s mass nervous breakdown took the form of a dance to the death.  
In the years since we have seen similar phenomena in ‘June Bug’ infections, mysterious poison gas bandits, Tanzanian laughing plagues, German Coca Cola ‘poisoning’s, an outbreak of Tourette’s-like symptoms in an upstate New York high school, spates of headaches, nausea and hearing damage among Americans in Havana Cuba, catatonic trances among refugees in Sweden – and so on. It is very likely we can add the dancing plagues of medieval Europe to the list of psychogenic, rather than physical – or even metaphysical – phenomena.