Weird diseases are one thing. But what happens when a weird disease starts to spread, eventually affecting dozens, hundreds, even thousands of people in various areas around the world? There are stories of unexplained maladies, from a disease that leaves you dead in a puddle of sweat within hours, to epidemics of uncontrollable dancing, to hundreds of people pulling on their private parts (yes, this is a real thing). These are the strangest epidemics of all time.