"Prions" cause Creutzfeldt-Jakob in humans, fast deadly dementia, Mad Cow in bovines etc etc...and it appears they are finding viral agents that debunk the prion HYPOTHESIS.(Typical Scientist A vs. Scientist B war over the true cause of the weirder degenerative neurodiseases, so who knows)
Dementia patients don't act like zombies. Memory weirdness, strange behavior, psychosis sure, but most of them are too agitated to act zombie-like. Scared, confused, worried over some rap from 1947 they think is happening.
Your neighborhood crackhead or 102 year old grandmother mebbe. The 28 movies would be closer but it's so fast the infected drop dead too quickly for the decline to display zombieness other than on their death beds.
However there is higher incidence in culture with cannibilism of neural tissue. Happens a lot when humans eat brains. So that's interesting/spooky/cool whatever.
Not trolling on anyone but my vote goes to the "voodoo" neurotoxins long since proven above.