Real Life Imitating 'The Simpsons'

Many years ago I saw an episode of 'The Simpsons' where Mr. Burns learned the only thing keeping him alive was that every disease was trying to infect him at once and so they all blocked each other.

With this in mind see this at The New Scientist: Common cold may hold off swine flu

"We think that when you get one infection, it turns on your antiviral defences, and excludes the other viruses,"

And this special I recently saw on PBS regarding how descendants the survivors of Europe's black plague carry a mutation that also makes them immune to HIV: Mystery Of The Black Death