[Fomite]

While you might argue that development was a net positive overall, we didn't actually learn a whole lot from it - plague was a recurring problem in Europe for centuries. For example, major epidemic we all think of as "The Black Death" kicked off in 1347, but there were still major outbreaks (the Great Plague of London) in 1665.

If any one disease is responsible for hygiene and disease prevention in the west, I think you can make a much stronger case for the Cholera outbreaks in the mid-1800's.