I believe this theory May be correct Dr. Jannson. Consider other undead sources, such as the Vampire. In the historical documentation of Blade versus Dracula, Blade won by attacking the red cells of Dracula. It was the cells that kept him and all other vampires alive. With this knowledge one would assume that the typical Zombie shared some of the same characteristics of the vampire at least on a cellular levl. I further imply that perhaps the occurence of Zombies could even be attributed to half turned vampire victims.
"When I let Go of who I am, I become who I might be."