Theories about the causes and cures of dancing mania
John Waller, Dancing Plague: The Strange, True Story of an Extraordinary Illness (2009) argues that the Strasbourg dancers were exhibiting extreme penitent behavior:
The people of Strasbourg danced in their misery due to an unquestioning belief in the wrath of God and His holy saints: it was a pathological expression of desperation and pious fear.
Whether contemporaneous Strasbourgers shared that understanding of the dancers, they certainly seemed to see a supernatural element in the phenomenon. Here is Waller's account of the reaction to Frau Troffea, whom he credits with beginning the Strasbourg episode of dancing mania:
They watched as Frau Troffea's dance went on deep into the third day, her shoes now caked with blood, sweat trickling down her careworn face. Speculations flew among the onlookers. We are told that some blamed restless spirits, demons that had infiltrated and commandeered her soul. Perhaps through sin, they said, she had weakened her ability to resist the Devil's powers. But the crowd soon decided that this affliction had been sent from Heaven rather than Hell. Accordingly, after several days of violent exertion, Frau Troffea was bundled onto a wagon and transported to a shrine that lay a day's ride away, high up in the Vosges Mountains.
"Sick Body, Sick Brain," in Harper's New Monthly Magazine (December 1854) offers this brief account of the Strasbourg "dancing plague":
A similar lunacy broke out some time afterward at Strasburg, where the dancers were cared for by the town council, and conducted to the chapel of St. Vitus, a youthful saint, martyred in the time of Diocletian. For this saint, because little was known of him, a legend could be made suited to the emergency, in evidence that he, and he alone, was able to cure the dancing plague. The plague, however, spread; and, as physicians regarded it as a purely spiritual question, it was left to the care of the Church, and even a century later, on St. Vitus's day, women went to the chapel of St. Vitus to dance off the fever that had accumulated in them during the past twelvemonth.
"St. Vitus," in Chambers's Journal of Popular Literature (August 22, 1857) reports that ecclesiastical treatment of the mania was aggressive:
By the year 1418, the dancing-plague had reached Strasbourg, and for many, many years, periodical attacks of the mania returned again and again. The priests used to pray to St. Vitus, and to throw cold water over the dancers; they would also beat them with sticks, and read the Gospel of St John to them.
It is unclear to me whether the reports citing the year 1418 and the year 1518 refer to the same events or to events that coincidentally occurred exactly 100 years apart.
J.F.C. Hecker, The Epidemics of the Middle Ages (1844 translation of a work published in German in 1832) discusses the regimens recommended by Paracelsus (who visited Strasbourg in 1518) for treating two of the three varieties of the dancing sickness:
For the first kind, which often originated in passionate excitement, he had a mental remedy, the efficacy of which is not to be despised, if we estimate its value in connexion with the prevalent opinions of those times. The patient was to make an image of himself in wax or resin, and by an effort of thought to concentrate all his blasphemies and sins in it. "Without the intervention of any other person, to set his whole mind and thoughts concerning these oaths in the image;" and when he had succeeded in this, he was to burn the image, so that not a particle of it should remain. ... For the second kind of St. Vitus's dance, arising from sensual irritation, with which women were far more frequently affected than men, Paracelsus recommended harsh treatment and strict fasting. He directed that the patients should be deprived of their liberty; placed in solitary confinement, and made to sit in an uncomfortable place, until their misery brought them to their senses and to a feeling of penitence. He then permitted them gradually to return to their unaccustomed habits.Severe corporal chastisement was not omitted; but, on the other hand, angry resistance on the part of the patient was to be sedulously avoided, on the ground that it might increase his malady, or even destroy him : moreover, where it seemed proper, Paracelsus allayed the excitement of the nerves by immersion in cold water.
Perhaps the most interesting thing about Paracelsus's recommended intervention in cases of dancing mania is that he dismissed supernatural explanations of the disorder's cause—and yet his therapeutic methods of concentrated penitent thought, restraints, corporal punishment, and immersion in cold water have much in common with the priests' practices of praying, beating sufferers with sticks, and sloshing them with cold water, noted above.
Hiring musician and dancers to exhaust the afflicted
Robert Burton, The Anatomy of Melancholy (1621/1638) mentions that government officials would hire musicians to play music for people afflicted with dancing mania. In fact, Burton uses the present tense to describe this treatment:
Chorus Sancti Viti, or St. Vitus Dance; the lascivious dance, Paracelsus calls it, because they that are taken with it, can do nothing but dance till they be dead, or cured. It is so called, for that the parties so troubled were wont to go to saint Vitus for helpe, and after they had danced there a while, they were certainly freed. ... Musick above all things they [the afflicted] love, and therefore the Magistrates in Germany will hire Musicians to play for them, and some lusty sturdy companions to dance with them.
For his part, Hecker offers this rather cursory explanation of the rationale behind hiring musicians and sturdy dance partners as curative measures:
That patients should be violently affected by music, and their paroxysms brought on and increased by it, is natural with such nervous disorders; where deeper impressions are made through the ear, which is the most intellectual of all the organs, than through any of the other senses. On this account the magistrates hired musicians for the purpose of carrying the St. Vitus's dancers so much the quicker through the attacks, and directed, that athletic men should be sent among them in order to complete the exhaustion, which had been often observed to produce a good effect.
Hecker then points to an account (from before 1615) of authorities in Basel, Switzerland, "having commissioned several powerful men to dance [successively] with a girl who had the dancing mania, till she recovered from her disorder"—a process that took more than four weeks but resulted in the girl's eventual recovery, after she collapsed from exhaustion and was carried to a hospital. Presumably the theory was that if the treatment didn't kill you, it would cure you.
I am not persuaded that "local physicians, who ruled out astrological and supernatural causes" (mentioned in the Wikipedia article) were responsible for the decision to hire musician and pace-setting dancers to wear out the afflicted—if, indeed, that tactic was adopted in the 1518 Strasbourg instance (which is not at all clear from Hecker's account). As noted above, Paracelsus (whom Hecker credits with opposing the prevailing theory that the dancers were possessed by demons or suffering from divine punishment) did not approve of encouraging the dancers to continue dancing. If the authorities accepted Paracelsus's opinion that dancing mania was a "natural disease," it is unclear why they did not adopt his recommended treatment of it as well.
The other possibility is that the authorities did view the dancers' behavior as having a supernatural element, Paracelsus's opinion notwithstanding. If the authorities interpreted the dancing in an outbreak of dancing mania to be the result of demonic possession, it seems odd that they would have tried to expel the evil spirits by, in effect, pumping up the volume. But if they viewed the dancing as constituting either a punishment from God or an exercise in penance by the dancer, they might well have viewed its continuation as a form of purification and perhaps sought to hasten it along by keeping up the beat.