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Patient Zero was two days ago, and the infection is spreading.
The news doesn’t know what’s going on. People are raiding supermarkets, grabbing tinned soup, crossbows, paracetamol and whatever you’re meant to stockpile in these situations. There’s traffic clogging the freeways. And all you can think is, “Oh, god… Zombies are coming. What the hell should I do?”
It sounds like a scenario designed to entertain overenthusiastic horror fans. But it turns out some well-credentialled scientists have also been wondering how humanity might react to a shambling, implacable, brain-eating zombie horde. Can science devise an optimal Zombie Survival Plan? Or should we all just go to the Winchester, have a cold pint, and wait for all this to blow over?
“It’s an interesting challenge, isn’t it?” asks Professor Greg Foliente, manager of The University of Melbourne’s Centre for Disaster Management and Public Safety (CDMPS). He pauses to readjust his frameless glasses before cutting to the chase. “From what we can see, there are really two options: run away and isolate the zombies, or put a ring around the infected area.”
You might have guessed, but modelling undead plagues is not the professor’s day job. The centre Foliente manages typically uses spatial simulations to analyse bushfires, disease outbreaks, hurricanes and other non-supernatural disasters. But earlier this year, when a software developer wanted to promote the Australian release of its latest zombie video game, State Of Decay 2, they gave the Melbourne academic a call. “They said, ‘Can you do some modelling of potential zombie infection rates in Australia and New Zealand?’” Foliente wasn’t sure: fiction enquiries were usually handled by the Arts Faculty a few buildings over. “But the CDMPS is interested in the potential outbreak and spread of epidemics,” he reasoned. And what is a zombie apocalypse if not an epidemic?
Foliente agreed to help, and assigned staff to plot out how an outbreak might go down. Surprisingly, they didn’t have to start from scratch. After a little digging, the team turned up a 2014 Cornell study titled Perturbations in Epidemiological Models: When Zombies Attack, We Can Survive! It proved a useful starting point, and led them to the field’s most influential work: When Zombies Attack!: Mathematical Modelling of an Outbreak of Zombie Infection, written by a Canadian professor named Phillip Muntz in 2008. Based on this research, the outlook seemed bleak. “An outbreak of zombies infecting humans is likely to be disastrous unless extremely aggressive tactics are employed,” Muntz wrote. “The most effective way to contain the rise of the undead is to hit hard and hit often.”
Stuffy academics were one thing. But Foliente’s team even managed to find some military scholarship on the subject. It turns out the Pentagon has an official plan for combating zombie apocalypses: CONPLAN 8888, which rates the threats of everything from “pathogenic” (virus-like) zombies to “vegetarian” ghouls that only consume plants. (The latter were unsurprisingly placed pretty low down on the Pentagon’s hierarchy of threats.) CONPLAN 8888 also outlines a contingency plan for dealing with zombie chickens – the only known zombies to actually exist in real life. (So-called ‘CZs’ occur when old hens that can no longer lay eggs are euthanised, buried, then claw their way back to the surface. The paper notes, perhaps unnecessarily, that “CZs are simply terrifying to behold.”)
Foliente’s next task was to take this existing research (minus the chicken stuff) and devise a specific mathematical model for an Australian and New Zealand outbreak, detailing how fast a plague might spread and which cities would be most at risk. “Our model is based on what’s known as a stochastic process,” Foliente explains. “Which means there’s an element of randomness. When there’s an interaction between a zombie and a human, if the human kills the zombie, the zombie is taken out of the zombie population. But if the zombie wins, the human obviously becomes a zombie.”
As with any proper scientific study, some solid definitions were in order. ‘Zombie’, in this case, referred to the classic, brain-dead, shuffling corpse. Likes: brains, human flesh, other zombies. Dislikes: head wounds, shotguns, flaming torches. These guys first drooled into the zeitgeist courtesy of George A. Romero’s 1968 film, Night of the Living Dead, but their origins date back to the Afro-Caribbean belief system known as Vodou. Depending on which horror film or Haitian myth you ascribe to, a zombie might have different characteristics and abilities. For the sake of consistency, the CDMPS model assumed a few basic rules:
- A zombie bite is enough to infect a human.
- In a one-on-one encounter, a zombie is likely to bite a human.
- Zombies can only walk and run. They can’t fly planes or ride mopeds.
- The humans will stay in their home cities rather than flee to the outback.
The Melbourne team let the model run, and were surprised by the results: high-density centres were actually better equipped to fight a zombie outbreak than low-density ones. “In Melbourne and Sydney, more people get infected because of population density,” Foliente says. “But the actual rate of spread is slower, because people can team up and help each other.” In smaller towns like Darwin or Queenstown, the rate of spread is also slow – there are simply not that many people to eat. Interestingly, it’s the medium-sized cities like Geelong, Perth and Auckland that are at the greatest risk of being overwhelmed: there are enough brains to go around in these places, but too few to organise and fight back efficiently. According to Foliente’s model, zombies would engulf these populations in a matter of days.
The team knew that geographical factors would also determine how the outbreak would spread. However, as most serious zombie studies had been conducted in North America, research on how the undead would behave in a sparsely populated island nation like Australia was scant. The CDMPS crew rolled out their maps and began crunching the data. “The U.S. has a lot of smaller towns connected to one another,” Foliente concluded, “while in Australia we have more isolated cities and towns, with great distances between them. This slows the spread of infection, where in the U.S. the virus just keeps going and going.” The team also reasoned that as Australia and New Zealand are islands, any infection would probably arrive through an airport. In the case of flying zombies, Sydney airport apparently has the best chance of containing the outbreak, due to the large surrounding population. If the zombies land at Tullamarine in Melbourne, the locals won’t stand a chance.
These new findings raise some interesting – and slightly uncomfortable – Darwinian conundrums. Statistically, humanity’s chances of surviving a zombie attack increase if everyone stays and fights together. Unfortunately, so do your own personal chances of being dragged down and eaten alive. “It’s a classic case of community needs versus those of the individual,” Foliente says. “From society’s perspective, it’s better for everyone to fight the zombies to the death. But that requires a lot of people to sacrifice themselves.
All this is very interesting, but you might ask: what’s the point? Apart from a hypothetical plague of creepy chickens, why would scientists waste time modelling something that will never actually happen? The simple answer is that it’s not the zombies that matter – it’s the science. “I didn’t realise it would be such a useful exercise,” Foliente admits. “But by doing the simulation, we found that medium-density cities are actually more at risk, which is counterintuitive.” This gave CDMPS valuable insight into how very real catastrophes, like viral epidemics, might play out. Zombie spatial modelling could also help predict the spread of less obvious pathogens, like ideas. “Clearly the dead coming back to life is an unlikely scenario,” Muntz wrote in his seminal paper back in 2008. “But possible real-life applications may include allegiance to political parties, or diseases with a dormant infection.”
In the Pentagon’s case, using zombies to model disasters was quite useful: the undead are a good, non-specific enemy. For obvious political reasons, you can’t have an unclassified, highly detailed defence strategy titled What to Do When Russia Invades; that sort of thing leads to rather pointed diplomatic questions. Meanwhile, America’s Centers for Disease Control and Prevention has even used zombies as a way to engage citizens and prepare them for natural disasters. There’s an entire section of the CDC’s website dedicated to “Zombie Preparedness”. For what it’s worth, the agency recommends keeping an emergency kit in your house, stocked with water (“one gallon per person per day”), a utility knife, duct tape, bleach, soap and towels, non-perishable food, and medication. However, the authors note: “If a zombie bites you, you’re a goner.”
The only remaining mystery is why we’re so fascinated by zombies in the first place. Of all known apocalypses, zombie outbreak is probably the most gruesome, and least likely. Foliente says that’s one question he can’t answer. “I have no idea,” he says. “One day someone invented the concept of zombies, and now they just won’t die.”
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