Human nature is always greedy.
A mysterious virus shattered the peace of the past. Those infected became bloodthirsty monsters, their bodies remade over time: bones mutated, organs exposed.
They acquired a simpler, universally known name: zombies. No one remembers who the first infected person was. They became puppets of the virus, with eyes for nothing but fresh flesh and red blood.
Their numbers grew, and various factions profited from the chaos. Terror began to spread, even as the government continued to call it an ordinary riot.
The police were crushed under layers of pressure, while the military was manipulated behind the scenes.
A greater conspiracy came to light. No one could remain calm anymore.
Civilization and order were gone, replaced by endless chaos for all eternity. Welcome to a world of infinite mutation.