"Throughout the history of the AIDS epidemic, a few lucky people have avoided infection despite being exposed again and again. Now, researchers are traveling back in evolutionary time to understand why some people are resistant -- and in some cases virtually immune -- to the AIDS virus.
Studies released this week and last year suggest that the roots of AIDS immunity extend back for centuries, long before the disease even existed. Our ethnic backgrounds and the illnesses suffered by our distant ancestors appear to play a crucial role in determining whether our genes will allow HIV to take hold in our bodies."
Article: Wired News
Long story short, a small population of northern Europeans seem to be immune or at least resistant to HIV.