Originally Posted by NewChief
Walking Dead explains. Zombies don't actually eat for nourishment. As such, they don't need to eat flesh, they're only compelled to eat flesh. The only flesh they're compelled to eat, in the Walking Dead, is flesh that is living or very fresh. So, in effect, once the victim dies, they start to "turn off" from eating the victim. I do agree that there would be way more zombies that are half eaten (possibly missing legs/arms/etc...).
Virus based zombies would spread pretty fast. Just think about how quickly flu spreads every year.