Beginning of the End

It'll probably be someone in a third world country who gets infected by something and someone from a first world country will need something that they have and are willing to get it cheap (the black market), such as some skin, a new organ, maybe even an egg or sperm from some unlucky individual.

This will most likely take place within the near future, seeing as how with everything the way it is today, someone will get desperate enough to try this out. But unlike the many before them, they will be Patient Zero. Poor bastard.