If you have 1 zombie left it WILL eventually die out whether it has hit you or not. Thats why the general safe thing to do is have 2 normal zombies alive as they walk and they will not die out (unless they are on side of bus hanging on and like the bus makes a turn like it does when leaving Diner) as they will not die out so long as another is alive still. The way things work in BO2 zombies is different then BO zombies.
"So... are you satisfied now?", Zelkova______________Gamestop Manager