I believe that the zombie apocalypse will not only happen, but every time you drive your car, drink some water, or decide to have four babies, you're causing our government to make it happen.
The single greatest deterrent is not nuclear war, it's the lost of the resources that will come from it. We are fretting over gas, we don't know where our food is going to come from, and the water... that's been going down hill for decades. Any war will cause the lost of these precious resources that we are throwing out of whack just by our Jackrabbit breeding. So how to secure these things?
A bio-attack. something that does not cause permanent damage to these resources you want. A bomb blows up on an oil field, and it's gone forever. But if a virus sweeps through the nation, there's minimal damage to the infra-structure and you're ready to loot.
Now, a dangerous airborne plague? Once you release that into the wild, that's it. That was your act of control. You have no idea how it will mutate, or if it will crop up again years after you think it's out of the area.
But a 28 days style rage virus that is limited to the bodily fluids of the infected, compels the body to spray said fluid constantly, and has a infection speed of only 28 seconds? that will spread like wildfire. But through humans*. You put that thing in LA now, by Saturday night, you'd probably have near decimation of the population. Although it couldn't just be one infection zone, you'd have to hit the center and key points around the city limits.
Also, Penn State is researching the Ophiocordyceps camponoti-balzani Fungus [http://www.dailymail.co.uk/sciencetech/article-2035531/Genetic-secret-virus-turns-caterpillars-zombies-discovered.html], also know as the Fungus that inspired Naughty Dog's new game The last of Us [http://www.youtube.com/watch?v=qLGxubfC1Ik] Also? Penn State isolated the Gene that allows for the zombie-ism.
So... How's your Bug Out Kit?
*I'm fully aware this could probably mutate also. But eh, I play games. We're a hopeful sort.