ParasiteZeta

Idea wise is close... parasites act as the virus that zombies are usually made of... except in this rpg the enemies are crafty... smart... and fast on their feet. Also the longer the parasite is inside the host it mutates into a stronger version of what it once was. Just like zombies... if a zombie stay alive long enough... the virus mutates and converts from being a slow zombie... to a maniacal sprinting zombie that stops at nothing to get it's next meal.

So you see... zombies and parasite infested hosts are not so different. But there are bother Zombies and smarter enemies. So it's a variety ^.^