The Washington PostDemocracy Dies in Darkness

Scientists determine the nation’s safest places to ride out a zombie apocalypse

The spread of a hypothetical zombie outbreak in the United States. (Courtesy of Alexander A. Alemi/Cornell University)
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The question was not an uncommon one. But the pursuit of an answer was.

Years ago, Cornell University researcher Alex Alemi was paging through some literature on zombies when the wheels started turning. What would happen, he wondered, if there was a real zombie outbreak? He lived in Ithaca, N.Y. How long would it remain secure? Tucked away in the hills of central New York, would it hold out longer than the region’s mightiest cities?

To be sure, in a country such as ours, where zombies maintain an entrenched position in the American zeitgeist, Alemi was not the first to express such curiosity. The zombie genre constantly pulses with new entries from Hollywood blockbusters to best-selling books to university courses at Michigan State University. But Alemi, who had just finished Max Brooks’s zombie novel “World War Z,” had a special skill that set him apart: He’s a statistician.

Since a zombie outbreak would, he reasoned, be like an outbreak of other viral diseases, he began to build a statistical model to determine what a “realistic” outbreak would look like. He and a team of other Cornell researchers will this week present their findings at the March meeting of the American Physical Society. Their work couples rigorous scientific methodology with the fantastical. Which, as Alemi pointed out in an interview with The Washington Post, isn’t that different from how researchers approach hypothetical outbreaks of real diseases.

But there is one snag, he said. “Zombies are unique and very different than other diseases in that victims of other diseases either get better or succumb to the disease,” Alemi, a Cornell PhD candidate in physics, told The Post. “But zombies are the undead. They don’t get better. And the only way to stop them is for a human to kill the zombie. With other diseases, no matter how many infections you model, the disease is not going to infect every single person. But in the zombie model, you really can turn every single person into a zombie.”

His interactive model, in which the user can design his or her own zombie outbreak anywhere in the United States with a click of a button, has its limits. For one, the only transportation the zombies have at their disposal are their own feet. Unlike Ebola, the models aren’t concerned with zombies using mass transit to quickly spread the virus. “Zombies do not fly airplanes,” as the research paper put it.

The model has several levers to dictate how quickly the outbreak moves. One is the “bite-to-kill” ratio, which measures how often a person would kill a zombie vs. how often a zombie would infect a human. Also, population centers are fixed — meaning if you live in Chicago when an outbreak strikes, you can’t escape. “Transportation would likely break down in an outbreak,” Alemi said. Even with those confines, Alemi said, “modeling zombies takes you through a lot of the techniques used to model real diseases, albeit in a fun context.”

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.

“New York City would fall in a matter of days, but Ithaca, where I am — it would take weeks for the zombies to make their way up here,” Alemi said. “It would be a situation where you’re watching chaos on television, but where you are everything would remain unchanged.”

Indeed, watching the virus seep across the United States is like watching a flame seek out its next source of oxygen. The spots with heavy populations are gobbled up at a dizzying rate, but the virus slows in underpopulated regions, leaving them more or less protected. If the disease were to begin in the heart of New York City, other big cities such as Boston and Washington, D.C., would be gone within days, if not hours. But in more isolated places, like the northern reaches of Vermont and New Hampshire, there wouldn’t be a zombie in sight.

The key to surviving the zombie apocalypse — though Alemi contends it would eventually kill us all — would be to live as far away from a city as possible. For example, he said, the underpopulated region between Los Angeles and San Francisco would be just as susceptible as those metropolises for the simple reason that they’re in close proximity.

It’s not enough to live in a sparsely populated area. Survivors would likely inhabit regions like central Nevada or the Colorado Rockies, far removed from any other city. “It’s bad to be near any big city,” Alemi said. “Just look at the population map. First, you’d benefit from the fact that it would be highly unlikely for the zombie outbreak to begin where you are, and then it would take a very long time for any zombies to get out there.”

But don’t move yet! A rush to underpopulated regions would, in fact, only make them vulnerable. Plus there’s the fact that, you know, zombies are make-believe.

But hey, always good to be prepared. Because even in the American hinterlands, it would be “on the order of years,” Alemi said, before the first zombie arrived.

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