A “realistic” zombie outbreak, as Alemi calls it, both conforms to popular interpretations — and breaks them. For instance, densely populated regions are just about the worst place to be, a fact assumed in any number of zombie flicks. But unlike the movies, which often depict diffuse saturation and numerous locations simultaneously affected, a true outbreak wouldn’t work like that. It would take hours, days, months and even years to spread into every underpopulated nook and cranny of the United States.