Perhaps some races are less likely to get certain diseases?
Biologists Discover Why 10 Percent Of Europeans Are Safe From ...
http://www.sciencedaily.com/releases/2005/03/050325234239.htm
Apr 3, 2005 ... These plagues were also confined to Europe, persisted for more ... fever that used the CCR5 as an entry port into the immune system. .... could potentially control and perhaps end the HIV/AIDS pandemic. ... might constitute an innate defense against infection with the human immunodeficiency virus (HIV).
What if you’re immune to HIV? | POSITIVE LIVING BC
http://www.positivelivingbc.org/news/110928/what-if-youre-immune-hiv
Sep 22, 2011 ... ... the early findings like this: “An estimated one percent of people descended from Northern Europeans are virtually immune to AIDS infection…
Northern Europeans who were immune to bubonic plague passed this immunity on to their offspring and they seem to be immune to AIDs. I am most likely immune to AIDs but I do not risk it anyway! Better to be safe than sorry.