In my universe, the original Birkin injected himself with the G-virus and ended up mutating, eventually being killed when Raccoon City was destroyed. That was... let me see, something like eleven years ago now. In any case, when the Birkin on the community joined, he was from a time prior to his death. I had him worldhopped out before he could die. How that affected his original universe, I neither know nor care, and it seems to have had no adverse effects on my own.