Aarian Marshall is a transportation reporter at WIRED and former CityLab contributor. She lives in San Francisco.
Researchers at Cornell University modeled what would actually happen if zombies attacked. Spoiler: The news is not good for city-dwellers.
Where would you run if zombies attack? The best place in the U.S. to escape from hypothetical brain feeders, according to a new simulation from real-life Cornell University researchers that they will present later this week, is the Northern Rockies. Not on the list: your favorite densely populated metro area.
The Cornell simulation, which you can play with here, draws data from the 2010 U.S. Census and depends on the SIR model, an epidemiological model sometimes used to predict the spread of real-life infectious diseases like measles and rubella. In the SIR model, individuals are either susceptible (S), infected (I) or recovered or immune (R) from a disease. But with zombies, of course, there's a bit of a twist: Once a zombie, always a zombie. There are no R's here. As Alex Alemi, one of the Cornell researchers, told NewScientist, "Zombies don't get better, nor do they die, so the only way you can get rid of a zombie is for a human to actively kill it."
Not a huge surprise, but it turns out the speed of a zombie outbreak is highly dependent on the bite to kill ratio. That's the measure of how effectively zombies are snacking on humans, versus how effectively humans are killing zombies. When I set the bite to kill ratio to zero in the Cornell simulation—creating UNSTOPPABLE ZOMBIES—and dropped one in densely populated New York City, it was game over for the entire East Coast in about 3 days:
Of course, we humans wouldn't go down without a fight. By studying zombie lore, the Cornell researchers determined that a 0.8 bite to kill ratio is a bit more realistic. Under these conditions, zombies are roughly 25 percent more likely to bite humans than humans are to kill zombies. Given this more realistic scenario, I dropped another single zombie in New York City to see what would happen.
Once again, the Big Apple got real ugly, real quick. Within about 11 hours, zombies had chomped their way through much of the Tri-State area:
Within about 10 days, I and my Beltway brethren in D.C. were also undead. By day 23, they had noshed on my grandma in Detroit. Here's the zombies' progress about a month in:
As the researchers note, cities would give way to the hoard the quickest. (As they can and have in the face of other infectious diseases.) But it took the zombies weeks to, for example, penetrate the less populated areas of upstate New York. "Given the dynamics of the disease, once the zombies invade more sparsely populated areas, the whole outbreak slows down—there are fewer humans to bite, so you start creating zombies at a slower rate," as Alemi put it in a press release.
The good news? No matter where you drop your Patient Zero, the Cornell researchers found that it took months for any zombies to reach the northern Rocky Mountains.
It's an important lesson to take into account next time you have a nightmare. If and when the zombie does apocalypse come, how much time you have left will depend on where you are in relationship to the first outbreak. But it would also be prudent to abandon your favorite bike lane, mass transit conveyance, or neighborhood dive bar. Oh, ye urban faithful: When the zombies come, get out of the city.