From wikipedia:
The Dancing Plague (or Dance Epidemic) of 1518 was a case of dancing mania that occurred in Strasbourg, Alsace (then part of the Holy Roman Empire) in July 1518. Numerous people took to dancing for days without rest, and, over the period of about one month, some of those affected died of heart attack, stroke, or exhaustion.
hi! there's always room for more input, but FYI here have been a few posts on this, so check these out for previous discussions
Dancing Plague of 1518... This can't be real, can it? How did this happen?
Dancing plagues in early modern Europe: what's it all about?
I've taken a college course where this subject was the subject of multiple discussions. We referenced Barbara Ehrenreich's Dancing in the Streets (amazon link) and please someone correct me if I'm wrong since I've not read it in years, but she theorizes that the causes of the dancing plague is not unique to that period in time. For example, there is a movie named Joyeux Noel (imdb) where a spontaneous truce was called over the trench warfare during christmas.
Essentially, the theorized cause is lack of ability to collectively celebrate life with other people. Throughout history when human populations have no avenues to experience collective joy, spontaneous parties and dancing occurs. The current popular expression of collective joy is drama/theatre which celebrate tragic deaths and comedic rebirths.
What follows is my brief summary of her book according to my lectures:
Ehrenreich argues that the human need for dancing and merry making collectively have roots in our evolutionary history. Citing a theory that describes packs of early humans grouping up and dancing rhythmically for looking like a single organism to protect themselves from larger predators.
The topic of the college course (comic spirit) heavily related to dionysian ideas and Ehrenreich discusses how most human cultures have some form of dionysian or trickster archetype that encourages breaking down societal barriers. She notes that dancing and the shared feelings of letting loose accompany these celebrations across cultures. Hence, the main theory that dance is as basic to humans as humor or laughter. I'd like to expand more on her book but I've not read it in a while, but that's the part I remember that deals with the question directly.
The book has much information on the entire phenomena and I suggest you check it out if you want to find more sources.