On one calm summer morning, in the Alsatian city of Strasbourg, France, a certain woman who went by the name of Frau Troffea was suddenly overcome with an irresistible urge to boogie. She begun hopping and leaping into the air, restlessly dancing with an intensity that baffled the rest of the villagers. One day, two days, four days passed and still she danced with mindless rage, never pausing to eat, drink or sleep. Soon enough, others feverishly joined her, shaking about compulsively around the city - until the number reached 400 by the end of August 1518, and desperate Strasbourg officials were forced to admit that a bizarre and yet unknown affliction had struck their town. Some kind of dancing epidemic which was not only very bewildering but evidently very, very contagious.

Not knowing how to handle this odd case of dance-mania, doctors prescribed more dancing, thinking people would be cured once they had shaken their energy away ... Unfortunatly all did not go as planned, and the non-stop dancing resulted, chronicles agree, in dozens of heart attacks, strokes and deaths by exhaustion or starvation.

Historical records show of other outbreaks which occurred in medieval Europe ( most of them in the areas surrounding Strasbourg) but the epidemic of 1518 is by far the best documented. Modern historians have had many theories about the origins of this phenomenon: was it drug-induced ? Was it some form of heretical ritual? The most plausible explanation we have now is that these were episodes of "mass psychogenic hysteria caused by intolerable levels of distress". The reality of the Alsatian was so grim and people lived in such profound fear they started believing in an old Christian church legend about the wrath of St.Vitus, who supposedly would send down plagues of compulsive dancing to any who provoked him. Then again, it could just be the love of boogie...

For more info:
BBC - http://news.bbc.co.uk/today/hi/today/newsid_7608000/7608874.stm
Discovery - http://dsc.discovery.com/news/2008/08/01/dancing-death-mystery.html