https://www.scientificamerican.com/article/the-physician-who-presaged-the-germ-theory-of-disease-nearly-500-years-ago/

Renaissance Italy was full of new ideas; cultural and economic rebirth; and artistic fervor, and it produced some of the most notable scientific work Europe had seen for centuries. It was also a time of syphilis. The first recorded outbreak occurred in 1494/95 in the city of Naples, after which it spread rapidly throughout Europe.

As a physician in Verona, Girolamo Fracastoro observed the mortifying effects of the disease firsthand. More virulent and contagious than syphilis today, the disease would be responsible for an estimated five million deaths throughout the continent. Its symptoms were particularly visual and included widespread bodily lesions.