The zombie apocalypse never stops (Call of Duty franchise)
For researchers trying to discover the zombie strain source, look no further than the zombie game mode included whenever Treyarch develops a Call of Duty game. It seems like the outbreak stems from the first-person shooter franchise, as the endless game mode turns human brains to zombie mush. Countless hours mindlessly playing various zombie maps will have gamers asking “how many levels are there?” “How many levels can I survive?” “How many levels can friends help me out with?” Before they know it, they join and chase other zombies mindlessly across the screen. The zombie apocalypse never ends, it just infects more gamers.