I dislike horror, both watching and writing it, so someone can take this premise and run with it. Whether it actually becomes a good story is up to the writer’s skills and drive.
Premise: A shadowy MKUltra-type program accidentally produced your typical patient zero of the zombie apocalypse—the traditional mindless, plodding kind. The effect was produced by a psychedelic drug which causes acute and permanent euphoric hallucinations, where the patients higher/frontal lobe functions, as well as whatever other parts of the brain that direct self-preservation, turn off completely and they end up wandering aimlessly after what they are hallucinating about. The drug concentrates in the brain, and it’s found out that consuming the zombie’s brain matter causes similar euphoric effects. So you’ll end up with a lot of people who want to get permanently high by eating zombie brains, which in turn, turns them into zombies. So you have a non-negligible number of non-zombie folks running after real zombies to try and eat them.
It’s gross, as far as these things go, but there’s an interesting story in there.