Originally Posted by SD 328I

I like how the series doesn't follow the character plot lines from the comics exactly, makes things interesting for those who already read them.

As mentioned, the "Walking Dead" refers to the humans still alive (Confirmed by the Producers), and the zombies probably follow the Romero Zombie rules. Which is anyone who dies will become a zombie regardless.

This explains why it's so difficult to stop them, and why they took over the World so quickly.