Zombie Apocalypse is a zombie mod for RimWorld, the sci-fi colony sim. Zombies are mindless killers who attack living people indiscriminately. They have an infectious bite which is fatal to anyone unlucky enough to let themselves get bitten, and any infected human will eventually be reanimated as a zombie on death. In rare cases the zombie virus can go airborne. Once that happens all corpses, bitten or not, will reanimate shortly after death. Zombies are an interesting and unique challenge to face in the RimWorld universe, and they help to significantly increase the difficulty of the game.