On a slightly related note, I've wondered that about Lyme's Disease. I was reading old death records (part of genealogy), and read about a young woman (in her 20's) who suddenly developed severe arthritis, and dies within months. Sounded like Lyme's Disease to me, and made me wonder how prevalent its been in the past.
It's probably all due to not knowing enough. Another one, people died mysteriously in their sleep and now they suspect sleep apnea.