Just like anything else sweeping the nation, the biggest jump will be in the first week when no one (besides us, of course) knows what is going on and makes themselves available as zombie bait. Just like the documentary Zombieland pointed out, the stupide and the less mobile in society will be the ones afflicted the worst so evasion gets to be like masturbation- exciting at first but eventually pretty boring. So what you are left with is a zombie race of stupid, fat, and/or disabled people- not exactly an intimidating prospect considering I deal with this every time I shop at Wal-Mart. After the first week, the next "converters" will be the group dumbass of these Zombie Killing Patrols; granted, they are more physically able than the regular zombies, but hopefully the other members of their patrol will remember the promise they made to each other about killing each other before they turn, so 90% of those are gone. After a week the first group will rot away, followed very shortly by the people they infected, etc.
Unfortunately the nature of the zombie makes it very succeptible to failure- instead of Dawn of the Dead think Shaun of the Dead. After 3 weeks you could go outside, walk around, make noise, etc. and find that the zombies are more or less gone. There might be one or two that will come your way, but you would smell them long before they would get close, and you would be waiting with your weapon of choice.
Now, if one could create a virus or parasite that overrode the brain, overstimulated the amygdala and the adrenal glands, but kept the infected alive, you would be onto something. And if you could make this Beserker virus/parasite airborne, then we will have one hell of a zombie apocolypse to forward to. But if the infected are dead, just expect it to be a lot like winter break from your school days- sitting inside, playing video games, and waiting for things to clear up outside.
