Note that the diseases on your chart only go in one direction, from Europe to America. Why? I recall a looong time ago (1980s probably) in Discover Magazine Jared Diamond wrote an article called “The Arrow of Disease” that asked that question but I don’t recall what his conclusions were. Still, the question has stuck with me.
Gee that was hard to find.
Grab some intellectual honesty on the way out.
http://discovermagazine.com/1992/oct/thearrowofdiseas137
Which is probably a good thing as if diseases had hit Europe as hard as they did the Americas we would be speaking Arabic or Chinese now.