Prions are as close as it gets I guess...
the fictional zombies are dead and some writers have speculated on a mutated rabies virus (prion-like), that would kill the host and continue to use the body by keeping certain brain functions active. This is impossible of course.
The closest to a zombie we might ever see is a prion/rabies rage virus pandemic a la 28 Days Later.
You should read World War Z. A film is in production starring Brad Pit. :)