Dancing Plague of 1518

A Copper engraving of Hendrik Hondius's based on a painting of Pieter Bruegel's believed to be about the dancing plague

It seemed like any normal day in July 1518 for the people of Strasbourg France. A woman named Frau Troffea started dancing in the street without any music. People laughed and clapped at her, but people began to worry as she not only danced to the next day, she danced for six days straight with no rest. Suddenly the dancing became contagious and 3 dozen people joined her by the end of the week. And by the time August came around 400 people had joined in the dancing.
No one really had a clue on what was happening. Physicians of the time claimed that the people were affected by hot blood and were recommended to dance the fever away. People started dying from exhaustion, heart attacks, and strokes.

In response to people dying the physicians recommended more dancing. They erected a stage and brought in music hoping that this will help people dance away the hot blood faster. Their plan didn't work as it had brought in more people to dance. During the height of the dancing mania, at least 15 people died per day. In September the dancing ended as it had started.

This event sounds like it's a legend, but it was a true event. There is no doubt that this Dancing Plague did happen as it was well documented in the town. It wasn't even the only one to have had happened in the 16th century either as events like it happened in Switzerland, Germany, and Holland. None of the others were as extreme as this one though.
There are many theories on why this event happened. One of the bigger theories is that it was all due to mass hysteria. This time it was extremely stressful for the people of Strasbourg. there was a famine happening and many of the residents were suffering from malnutrition due to t it.

Other theories are that they could have ingested Ergot which is a fungus that grows on Rye and grasses like Wheat. When ingested it can cause poisoning and or death. Some of the side effects are hallucinations, spasms, and convulsions which would be a cause for the dancing. It is known as nature LSD. Another theory is that they were part of a religious cult causing them to dance.

SOURCES:

BBC

Historic Mysteries

Discovery

History

Web MD