This is a very common question, but i think its time we had a serious discussion about it
If everyone is in fact, already infected with the virus that causes reanimation, then what is it about a zombie's bite that kills you? is it the fact their flesh is so rotten that you get a bad bacteria infection and die? because antibiotics can fix that easily.
So if its not an infection, what is it? Surely there's no magical reason why you die(TWD doesn't deal in wizardry as far as i know).
I remember someone suggesting they give you a virus that attacks your immune system similar to a fast acting version of AIDS independent of the reanimation, but i think the writers said that it had nothing to do with a virus or something to that effect.