What’s your zombie survival plan? You have one; do not lie. Mine is simple: find a boat on the river, escape the city and travel north along the coast until finding somewhere nice and quiet and defensible, and wait for it all to blow over.
Getting out of major urban centres like London is maybe the most obvious survival strategy, no matter the type of zombie posing a threat – from the shambling undead of Dawn of the Dead, to the fast-running infected (yes, they do count as zombies) of 28 Days Later. The fewer the people nearby, the fewer the number of potential threats, whether zombies or bandits.
A paper published this month on arXiv by researchers from Cornell has some interesting findings about whether the most obvious strategy is the best one – and it might actually have some real-world applications, too, in modelling the behaviour of rampant infectious diseases.
The scientists – from Cornell’s Laboratory of Atomic and Solid State Physics – use the “popular fictional disease” that is zombie infestation as a way of exploring epidemiological models built to simulate flu and measles outbreaks. There’s a difference between zombies and other diseases, though, because of two things: bites are an unusual transmission method, and everyone who isn’t a zombie could (or at least should) be looking to destroy the brain of any infected individual to stop it spreading at all. For something like the common cold, one person living in a neighbourhood with a thousand people is going to infect more people than if they lived in one with only 50; but with zombies, every extra human is both a target and a threat.
The model they build takes this into account, so that if the average human is better at killing zombies than being bitten, you’re not going to get much of an outbreak beyond patient zero. “Even a ferociously virulent zombie infestation might fortuitously be killed early on by happy accident,” they write, and their model “allows the possibility that the humans manage to defeat the outbreak before it really takes off”. So far, so good – but still, bear in mind that the chances of killing off the zombie disease drop off considerably once only a handful of people are bitten, assuming that people tend to live all near each other and have a decent chance of coming into contact with the infected.
Knowing this, and realising that mine or your chances of surviving a zombie outbreak depend massively on how far away, on average, we are from other people during the day – “surely, a zombie in New York cannot bite someone in Los Angeles,” they write – the scientists have drawn up what they call a “lattice model”, throwing a huge grid over a map of the continental United States, with each grid square being roughly 3km2. They also use two films (Night of the Living Dead and Shawn of the Dead) as their reference for zombie behaviour, and assume that zombies are roughly 1.25 times better at biting people than people are at killing them. Combining all of this together, and they could model both how successful infections are within each grid, and how successful they are at transferring between grids, averaging out the results of multiple simulations with patient zero living within different grid squares in the lattice.
They found that within the first week, most of the American population would have been turned into zombies, with major cities and towns easily devastated. Yet, over time, things shift, because of population density – the coastal regions, with cities like Los Angeles, New York City and Washington DC, fall early; yet, outside of the major cities of the central regions like Chicago, zombies have less luck. They can’t walk across the countryside fast enough, in large enough numbers, to pose a threat to people living in more isolated areas.
After 28 days, cities aren’t the most dangerous places any more – instead, it’s the suburban and rural places that are in between major population centres. Otherwise dull and quiet towns like Bakersfield in California, or Scranton in Pennsylvania, become extremely dangerous, as zombies move out of the biggest cities and along major highways to try and find more food.
The big surprise, though, is that even after several months sparsely-populated states like Montana remained almost entirely unscathed. It turns out that, as long as you can survive the first week and get to somewhere isolated, your chances of surviving the zombia apocalypse are pretty good. You might even be able to start thinking about repopulation, once they’ve fully decomposed and the vultures have done their work.