So, in the PBS Black Death thing, a genetic researcher was trying to figure out why some people survived close contact with bubonic plague without dying. He focused on one English village that quarantined itself for a year when they first saw signs of the plague, gathering DNA from descendants of known survivors. Upon matching up their DNA, they all had a particular mutation that likely gave them resistance or immunity (people having two copies of the mutation). This same mutation is largely absent from the rest of the world, but highly concentrated in areas that experienced the plague.
Interestingly, this mutation also gives resistance or immunity to HIV. One particular man with two copies of the mutation saw eighty of his friends die of AIDS in the early eighties, was performing the same activities, but never contracted HIV. Attempts to infect his blood in a laboratory with HIV always failed.
I found all this fascinating and had to share. Thank you for reading.