In 1518, Strasbourg was struck by a strange event known as the Dancing Plague. Hundreds of people began dancing uncontrollably for days, with some reportedly dancing to exhaustion or death. No clear cause was identified, though theories include mass hysteria, a neurological disorder, or poisoning.
The phenomenon lasted about a month and baffled medical and religious authorities. Attempts to stop the dancing included isolation and prayers, but nothing seemed to work. It remains one of history’s most peculiar mass psychogenic illnesses.