Oh I know, absolutely. Also, a virus infecting the brain would be nearly impossible, what with the blood brain barrier, and a virus changing the very nature of the brain from aerobic to anaerobic would be impossible.
That's why I theorized that whatever made zombies was actualy some kind of parasite, maybe a micro-organism, that controlled some parts of the brain that allowed for movement and interpretation of signals from the sensory organs, and lived off the rest of the brain. This parasite would pass itself from host to host through direct body fluid contact (saliva, blood, etc.) So, its not the hosts themselves becoming zombies, more like complex puppets.
Anyways, it wasn't the plausibility of zeds that creeped me out, but the accounts themselves. I just have a wicked active imagination, and imagining getting eaten alive is not fun.