Perhaps more than any other disease before or since, syphilis in early modern Europe provoked the kind of widespread moral panic that AIDS revived when it struck America in the 1980s.
Medical research in the twentieth century mostly takes place in the lab; in the Renaissance, though, researchers went first and foremost to the library to see what the ancients had said.
Shortly after Christopher Columbus and his sailors returned from their voyage to the New World, a horrifying new disease began to make its way around the Old. The "pox," as it was often called, erupted with dramatic severity.
Even more than this, however, the sick - like lepers - were often reviled because people believed that they had brought their torments upon themselves.