Kirkman confirmed (at least for the comic series) that bitten animals die but don't reanimate, so no zombie animals
Imagine a group of a hundred motorcycles driving down a freeway. Eventually, they hit a junction. One road goes northwest and the other goes northeast. So one guy, we'll call him S, says, "Let's go northwest!" A mile past the intersection, a semi careens into the group and kills ninety of them. Ten are wounded, but they survive and keep going. Eventually, they hit 10,000 miles. S suddenly has his consciousness thrown into his past body right before the junction. Now, he says, "Let's go northeast!" All 100 bikers survive. Happily ever after, right? But what about the ten, no nine, who went northwest and survived? What happens to the reality they were living? Does it just disappear now that S has changed the past? It's not like only bad things happened on that 10,000 mile journey. Maybe one of them fell in love with a gas station attendant and got her pregnant or maybe one adopted a homeless kid that joined the adventure. That 10,000 mile journey would be full of stories. Romances, farewells, friendships...the loss of those ninety lives is horrible and unfortunate, but what would rewriting their history mean? The nine who survived lived full lives and did the best they could with the hand they were dealt. How could it be right to just erase all that? Isn't that worth something? Is there a point to a world where everything is happy? Are people who struggle for a better life just idiots? Being human is about fighting even when it seems hopeless and finding happiness in a world that hates it. Are you saying that's worthless?