The Dancing Mania or Dancing Plague remains an unresolved mystery. First seen in the 13th century, it continued to appear sporadically over the following three centuries. What compelled groups of people in Germany, Holland, Italy and other countries to engage in mass, frenzied dancing is still not known. Various causes have been suggested, including demonic possession, the bite of a tarantula, epilepsy, ergot poisoning and social adversity - the real cause may be a combination or none of these.