I’ve been watching and for the most part enjoying “Walking Dead” on AMC. And like most folks that watch I have my own ideas about zombies.
In general my concepts could probably be assigned to any number of zombie stories. But I use Walking Dead as a basis because it’s current.
First off, how the outbreak began. It had to be either an air born or water born event.
It can’t have been just the recently dead reanimating. The relatively small number of bodies would have been easily contained. I imagine an event infecting a large part of the population like a plague. Rapidly killing them, leaving thousands to reanimate.
Now for the cause of the “virus”. A government accident is to easy and expected.
It’s an alien plot. Here’s how I see it. Aliens covertly disperse the zombie virus into the atmosphere. Thousands are turned into the walking dead. More are killed by the walkers. Survivors are left scattered and disorganized. After a year or so the aliens return, release an antidote. The walkers drop dead(again). With little resistance, there is nothing to stop them from raiding the planet for resources or even colonization. ( even as I right this it occurs to me the virus may even be an atmospheric prep for the aliens themselves )
Anyways that’s where my theory goes.
Thoughts from my head 