From the Writer's Almanac (24 June 2011):
An outbreak of dancing plague, also known as St. Vitus' Dance or epidemic chorea, began on this day in 1374 in Aachen, Germany. From Aachen it spread across central Europe and as far away as England and Madagascar. Dancing mania affected groups of people -- as many as thousands at a time -- and caused them to dance uncontrollably for days, weeks, and even months until they collapsed from exhaustion. Some danced themselves to death, suffering heart attacks or broken hips and ribs. Most outbreaks happened between the 14th and 17th centuries, though there are reports of dancing mania as far back as the 7th century. The 1374 outbreak was well-documented by several credible witnesses who reported that dancers sang, screamed, saw visions, behaved like animals, and experienced aversions to the color red and to pointy-toed shoes.
At the time, people believed the plague was the result of a curse from St. Vitus or St. John the Baptist, and so they prayed to the saints and made pilgrimages to their shrines. Exorcism was another treatment option, as was isolation, and many communities hired musicians to accompany the dancers in the hope that it would help them overcome their compulsion; it usually just resulted in more people joining the dancing. Scientists today are still at a loss to explain it, putting it down to economic hardship, ergot poisoning, cults, or mass hysteria.
Oh, and I totally agree on the part about having an aversion to pointy-toed shoes. They tend to catch rocks and roots, you know.