You're right about pretty much everything there, but I was watching the Talking Dead, and one of the producers was on. H e said that in those scenes like the highway, they made sure that all of the dead people you saw died of some visual trauma to the head. So I think that's the explanation for the dead bodies, they were either shot in the head and you can't really see it,or they had some other sort of damage to the brain, rendering it useless.

But who know's, the showrunners have been known to lie before, (to keep spoilers at bay, not to be intentionally mean or anything), so maybe some people are immune or it's something you breathe in. Though I think they're going to stick close to the comics and focus on the survival of the characters and not what's causing the outbreak

Also notice how when they come to certain area's the show emphasizes burnt bodies. In the town Shane went to, the garage was filled with burned boddies, the two cops had a burnt corpse near them, the first major city also had some.

Perhaps it was a virus at first, but was made to go airborne if the body is burned.

Like any disease some people will have a natural immunity to it. Hence why some of the corpses on the Highway never reanimated.

@Soldierone:

I doubt it was spread via the burning of victims, in fact, in Medieval Europe cremation was one the only effective ways of curbing infectious diseases. Fire kills practically every virus, and it definitely does not magically cause it to mutate into an airborne strand.

Another potential reason why some of the corpses might never have reanimated on the Highway, is because they were buckled in, trapped within their cars, with the windows rolled up and left to fester in the Atlanta summer heat. Which inhibited the virus from taking effect.

Robert Kirkman (the comic books creator & the executive producer of the show) explained how reanimation works:

...the rule is: WHATEVER it is that causes the zombies, is something everyone already has. If you stub your toe, get an infection and die ... you turn into a zombie. UNLESS your brain is damaged. If someone shoots you in the head and you die ...you're dead. A zombie bite kills you because of infection, or blood loss ... not because of the zombie "virus."

Shane died because of the stab wound, and like everyone else who dies and their brain isn't destroyed ( the kid Randall), the dormant virus in his system reanimated them.

@jony_dols: Robert Kirkman's explanation doesn't explain why Rick feels the need to chop peoples' limbs off in the comic when they are bitten there?

Didn't Dale get bitten and then Rick chopped off his leg to stop him from dying? From this, I would assume that a zombie bite can kill like some sort of poison.

I agree that a dormant virus reanimates the dead but I think a zombie bite is poisonous and can kill someone if it spreads throughout their body.

@cb4g

Exactly, the bite unleashes a massive infection which spreads very fast and than proceeds to kill the infected. By cutting off the limb where the bite is, they stop the infection in its tracks.

i'm pretty sure they will survive that one