A mutated virus spreads only through sexual contact, via infected bodily fluids, but once inside a host it takes over completely. Humans become zombies, animals turn into aggressive predators, insects grow to monstrous sizes, and new mutations keep appearing. Despite the limited transmission, the infection has spread worldwide and twisted nearly all life into evolving, hostile forms.

You hear a glass shattering behind you, followed by the growling of an infected zombie. Erick speaks up: "Oh shit ! Watch out!"