I have a question that bugs me quite a bit. Why didn't Rick get sick when he capped that zombie and got splashed with all that goo on his face and in his mouth? It cannot be doing good to him, especially when he has open wounds on his face.
Maybe the zombie blood doesn't contain the active infection. Characters who have painted their bodies with blood and assorted walker parts to camouflage themselves suffered no ill effects. Being bitten, though, seems to be a fatal event. Is zombie saliva the bodily fluid to be avoided?
I think the messed up the whole medical science behind how the zombie disease works so I wouldn't worry too much about it. Just suspend disbelief about that aspect. When they went to the CDC at the end of Season One, Rick was told the shocking reveal by Dr Jenner that everyone has the infection already. Which means it doesn't matter whether a zombie bites you are not, when you die you become zombie. That's why Lori had to be shot after the birth of Judith. Kirkman has since said that he wishes that never happened but that they didn't expect to get more than one or two seasons. Then you also have Hershel who walked around without one leg for a year. They amputated to stop the infection spreading from a bite, but if you don't die from a bite, why does it matter any more than hacking your leg off?