If I understand your question I would say AIDS, cancer, and diabetes to name 3, but there are many many more. There are diseases that are even hard to identify, let alone cure. I hope none of us get any of them.
As the (we) boomers age, I thought this might be good info to pass along.
Sorry, it was worded poorly. Are there many diseases that were prevalent in the past, that have been eradicated?