Ghosts, even if you died in the 1800’s, doesn’t mean you still gotta dress like it.

Zombies suck, evolutionarily speaking. A species whose only source of nourishment is also its only source of reproduction ( and it’s one or the other at every opportunity) is pretty much destined to collapse in a very short time. The only reason viruses can sustain it is that they basically die and revive only when the food / reproduction is is the immediate vicinity. They also reproduce at a ratio higher than 1:1.