I love a good science fiction that's just beyond reality. Things that could actually happen in the real world with a not-too-unlikely dice roll.

The Last Of Us for example: a known, real-world fungal spore that takes over its hosts body (ants) and uses it to attack and spread to other potential hosts; mutates to survive earth's rising temperatures allowing it to survive in and control larger warm-blooded hosts (humans).

Thus, real zombies that aren't the result of some total fantasy fabricated in a lab that fucked up somewhere.

It's more believable making the fear more real.