A zombie apocalypse is a particular hypothetical scenario of apocalyptic literature that customarily has a science fiction/horror rationale. In a zombie apocalypse, a widespread rise of zombies hostile to human life engages in a general assault on civilization.
In some stories, victims of zombies may become zombies themselves if they are bitten by zombies or the virus travels by air; in others, everyone who dies, whatever the cause, becomes one of the undead. In the latter scenario zombies also prey on the living and their bite causes an infection that kills. In either scenario, this causes the outbreak to become an exponentially growing crisis: the spreading “zombie plague” swamps normal military and law enforcement organizations, leading to the panicked collapse of civilian society until only isolated pockets of survivors remain, scavenging for food and supplies in a world reduced to a pre-industrial hostile wilderness.
The founding work of the genre was Richard Matheson‘s novel I Am Legend (1954), which featured a lone survivor named Robert Neville waging a war against a human population transformed into vampires. The novel was later adapted into a screenplay, The Omega Man (1971), starring Charlton Heston. George A. Romero borrowed the idea for his apocalyptic feature Night of the Living Dead (1968) but substituted vampires with shuffling zombieS.
