Ever wonder how the zombie apocalypse would spread across the United States of America? Shows like The Walking Dead have done a good job of dramatizing what things would look like on the ground, but we never really got to see how things progressed from a more scientific point of view.
Until now. Programmer Matt Bierbaum has created a website called Zombietown USA, a “disease dynamics simulation of zombism across the USA” using “Gillespie dynamics on block level census data from 2010 using 308 million people interacting across the continental U.S.” I have no idea what any of that means, but it sure sounds sciencey to me. Here’s how they explain it:
We start with a simple model of zombies, the SZR model. There are three compartments in the model: S represents the susceptible population, the uninfected humans, Z represents the infected state, zombies, and R represents our removed state, in this case zombies that have been terminated by humans (canonically by destroying their brain so as to render them inoperable). There are two transitions possible: a human can become infected if they are bitten by a zombie, and a zombie can be destroyed by direct action by a human. There are two parameters governing these transitions: β, the bite parameter determines the rate at which a zombie will bite a human if they are in contact, and κ the kill parameter that gives the rate that a human kills the zombie.
As cool as it is, this seems like an incomplete simulation — the current iteration has the zombie plague spreading at the speed zombies can shuffle along on foot. We all know what would really happen; bitten and infected people would drive cars and hop planes and do all sorts of other dumb stuff to increase the speed of infection.
Then there’s all the other variables not taken into consideration — lockdowns, quarantines, wiping out overrun areas with bombs. Okay, perhaps we’re asking too much from this disease simulator. If you want to see a graphical representation of the spread of infection based on a couple of variables, play with this thing. If you want a more involved breakdown of how it would all play out, just read World War Z. The book, not the movie.