It started in the Middle East.
A flu-like plague that infected thousands and killed roughly ten percent of its victims. Those who died awoke once again, but they were no longer among the living--they came back as soulless carnivorous corpses who desired only one thing: to feed on living human flesh.
As the infection spread
across Europe and the rest of the globe, cities were overwhelmed. Nations fell. Humanity flickered like a candle flame in the wind.
In the United States:
the nation's great cities become hunting grounds. New York, Washington, Chicago, Los Angeles...all fall victim to hordes of shambling dead who want to devour the living.