(inspired by Joe McKinney's "Dead City" and "Apocalypse of the Dead", but generally applicable...I'm looking at you, "28 Days Later" in the back, there):
Dear Zombie Story Authors,
As much as I, your reader, appreciate a commitment to verisimilitude, and as much as pseudo-scientific explanations of how a zombie apocalypse could be "real" are fun, please stop trying to explain it away as a brain disease that affects living human beings, giving them superhuman pain tolerances and a mindless, ravenous appetite for human flesh. Because you then proceed to treat your "infected" just like they were zombies straight out of a Romero movie, which drastically undercuts the very sense of realism you were trying to create.
Look, we all understand that willpower is an amazing thing, and that people can do incredible stuff when they're sufficiently determined. But I have news for you. When your femoral artery is severed in the course of a zombie attack, it does not matter how determined you are to get up and eat the flesh of the living. You're going to bleed out in a matter of minutes, your circulatory system is going to collapse from hydrostatic shock, your brain is going to be completely deprived of oxygen, and you are going to die. Likewise, mindless determination to keep moving, hunting, and killing is not going to protect you from the rigors of exposure in the midst of a North Dakota winter. Starvation, dehydration, and blood loss are absolutes, even if determination can temporarily overcome them.
In essence, the human body is a machine, like an automobile. You are trying to describe the ways this machine can malfunction to produce a specific effect, and that's good, but please stop explaining to me how it keeps going without wheels, gasoline, or a functioning engine.
Thanks in advance,