Timothy Olyphant is awesome (see: Deadwood), and while I haven’t seen his new movie “The Crazies” yet, I have been thinking about it.
I haven’t done any real research on the subject, but as far as I can tell, the oldest “everyone around me turns into a zombie/vampire” story is Richard Matheson’s I Am Legend. It came out in 1954. Before that you have stories about one (or a few) members of the community going bad i.e. turning into a vampire, but nothing on the scale of today’s zombie apocalypse scenarios.
I think it has something to do with urbanization. When we lived in small villages, we knew everyone around us. It was far more likely that one member would turn on the group (go zombie) than it was the entire group would turn on you. Now we’re surrounded by literally thousands and even millions of strangers, and some part of our brain doesn’t trust them.