I doubt that we'll ever find out what caused the dead to rise. However, I gave some thought to what another poster said about 50K people dying per week. I agree that slow-moving zombies would not pose too much of a problem if people knew what they were dealing with.

However, think about it like this: 50K dead arise, all over the nation. They bite an average of .5 people each. That's 25K more. Society collapses, which accounts for more deaths. Power outages alone would kill of thousands of folks, depending one the time of year and the locations (folks in cities would be more vunerable). We've "only" got about half of the population that own guns, only a few of them would be able to shoot something the size of a head from 20 feet away. The ones left behind would be divided into the lucky, the decent and the mean... and the mean ones would start trying to take from both the decent and the lucky.

We also have to think about the religious ramifications. There would be mass suicides, which would lead to more undead, etc. I could envision something like this ending the world as we know it even if the zombies move slow.

I'm getting ready now. LOL