I have a hypothesis zombification could be as a result of a highly infectious virus. This does make a lot of sense, from a biologist’s point of view. Let’s call the virus ZAIDS. With this hypothesis, the virus works just like the Human Immunodeficiency Virus (HIV), where it enters the bloodstream, attaches itself to the white blood cells and releases its genetic material into the cell. Basically, the white blood cell would now begin to produce the DNA of HIV, and so more members of the virus are created, with the human cell being the controlled host. Only thing is that for zombies, the brain would have to be taken over, so the ZAIDS virus would enter the brain cells and do the same thing.
Think of it this way: the viruses enslave the brain cells to produce their offspring. Of course, all severe viruses (or all infectious viruses for that matter) have epic physical bodily effects, and because ZAIDS would attack the central nervous system (brain), there would be effects all over the body, you know, cuz the brain controls all. One such effect could be multiple organ dysfunction, since brain signals to the vital organs would be warped or stop completely. Also there would be severe mental disorder, which leads to their wacko behaviour. To me, it seems plausible, but hey, it’s still a hypothesis.
Gonna eat potato chips now. Please, don’t contract ZAIDS.