I recently just saw part of the first episode of the walkin dead, and I have to say the most horrifying part was when Rick (and subsequently we) saw that ravaged body of the nurse on the floor of the hospital. It begs the question that since her head was still intact, why wasn't it zombified? Anyways, I have read that in this universe, zombies outnumber humans 5,000 to 1. This means 1 of 2 things. One, it means that (assuming this all takes place in the 21st century) that there are about 1,400,000 humans left WORLDWIDE. Two, because of this, whatever the cause was, it was likely airborne or waterborne and caused about 6,998,600,000 to die/turn into zombies right away and the rest of the living, doomed to become zombies after they die. So this was a really bad thing, what could have been so bad that it made so many people die? Morgan from the first episode talks about a fever that killed his wife, a really hot one, but is that where the trail dead ends? A killer fever that's just so bad that it makes brain dead people come back to life? In the sense that they exist only to sustain themselves? Honestly I hope both the comic and show have a happy ending. They said the show will last for about 12 seasons so it'll be around for a while.