Black Death - Wikipedia, the free encyclopedia:
About 10 percent of Europeans have a gene mutation known as CCR5 delta 32 that disables a protein the Human Immunodeficiency Virus (HIV-1) uses to slip into immune system cells. Those with one copy of this gene have some immunity to HIV and those with two copies are virtually immune to the virus. This genetic mutation arose about 700 years ago and it has been suggested by some researchers that survivors of bubonic plague may have selected for the mutation. However, work published in 2003 suggests that smallpox was a more likely driver for the rise of the mutation.