This discussion may contain spoilers!
"He's bitten! That's how you TURN!" - Larry, S1E1 "A New Day"
In "A New Day" we are introduced to the walker disease, where it seems to resemble the most common, simple concept of the generic infection in zombie apocalypse media. Bitten by a walker = Become infected and turn into a walker through infection.
"It's not the bite that does it." - Ben Paul, S1E2 "Starved For Help"
But in "Starved For Help", we are already met with the apparent truth: Everyone is infected. No matter how you die, if the brain is not destroyed, you will become a walker.
So what exactly DOES the bite do, then? I'm not talking about the cases where a walker bites your neck open or digs into your insides. If everyone is already infected, how come even the slightest wound caused by a walker makes your days limited?
Is this is in any way explained in the original material of the comics? Please enlighten me.