Even more than this, however, the sick - like lepers - were often reviled because people believed that they had brought their torments upon themselves.
Often, city fathers blamed prostitutes for the disease, and some threatened to brand their cheeks with hot iron if they did not desist from their vices.
Was this an old disease, and, if so, which one? If it was new, what did that say about the state of medical knowledge? And in any case, how could physicians make sense of it?
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.
The idea of infection began to be taken far more seriously than it ever had before. Hospitals transformed themselves in response to the new plague - sometimes for the better, but often for the worse, as when, in fear, they cast their ulcerated patients out into the streets.