Critical Intel

The Pathology of Plague Inc.


Chinese authorities close a live poultry market in Shanghai and begin culling chickens, curbing the new H7N9 strain of Avian Flu. Meanwhile, in France, a hospital patient infects the man in the bed next to him with a virus he’s carried into the country from Dubai – a coronavirus related to SARS that’s been developing in the Middle East for a year or more. Rates of the fungal infection “valley fever” climb 900% over the thirteen years, as global warming parches the American Southwest and the fungus hitchhikes on dust particles. These real-life disease clusters are the domain of Plague Inc. a mobile game that casts the player as a wannabe pandemic hoping to wipe out humanity. The game has drawn attention from academics and game developers alike, but how accurately does it represent pandemic infections, and could an extraordinary virus really wipe out humanity?

Plague Inc. is an extremely entertaining game, but it’s hard not to read it as a wake-up call. Playing as the infection makes us think about how diseases function, the environmental challenges they have to overcome and how far a contagion can spread before it’s noticed on the world stage. “The game shows the player something unexpected by revealing the world to be a petri dish,” says James Vaughan, the game’s creator. “I think this lets players think about humanity from the outside, it lets them think about our weaknesses, how we live and how we care for ourselves.”

And Plague Inc. is very effective at communicating humanity’s vulnerabilities. Since the game’s release, Vaughan has regularly received emails from parents saying the game turned their kid into a diligent hand-washer. That’s understandable. It’s certainly made me pay more attention to H7N9 in light of my upcoming move to Hong Kong. Everything from the game’s news crawler – which displays “weird news” items and stories about “kickstopper” while a deadly infection expands unnoticed – to the comparisons to past pandemics, do everything but grab the player and shake them into awareness. This impact on the player’s thoughts and actions led to an interesting nexus between government, private industry and the public. On one hand, the disaster and event modeling company Risk Management Solutions (RMS) liked the game so much they asked to be included in the crawler text, and adopted Plague Inc. as a recruiting tool. Then in April, the Centers for Disease Control and Prevention invited Vaughan to speak about the game at their Atlanta headquarters, hoping it might inspire their team toward further public health outreach on mobile platforms. The lecture is part of an ongoing CDC strategy to reach the public through viral marketing and online zeitgeist – consider their Zombie Preparedness Campaign – which turns out to be an effective way to educate young people about public health. The fact that Vaughan built the app using publicly available data was a bonus as well.

“I supplemented it with lots of internet research – specifically on the mechanisms of disease, various symptoms and genetic concepts,” Vaughan told me by email. “For the country … information – the UN and World Bank have volumes of fascinating data which were extremely useful as it allowed me to ensure that the world of Plague Inc. is modeled as realistically as possible.”

The diseases themselves propagate realistically enough that there’s been some talk of turning Plague Inc. into an educational simulator. Vaughan put a lot of effort into developing the “infection cycle,” or how the disease affects patients and how those patients go on to infect others. Epidemiologically speaking, every disease has a basic reproduction rate (Ro), showing the number of secondary transmissions from a single source – i.e. the average number of people a single patient will infect. Ro raises or lowers depending on the characteristics of the disease: how long a patient is contagious, how infectious the organism itself proves to be, and the number of susceptible people a patient comes in contact with. Polio and Smallpox are a 5-7, for example, while Measles are a 12-18. Likewise, Plague Inc. models how easily viruses and other pathogens can jump borders in today’s highly-connected world, where international air travel, transshipment and regional livestock markets can help spread a pathogen. “In the past,” reflects Vaughan, “a disease would take years and years to travel from one side of the world to another – now that can happen in less than 24 hours!”

The game also takes world gatherings into account, meaning the World Cup or Olympics might spread the disease to a number of previously unaffected countries. Historically that’s happened a number of times, most notably during the 1918 influenza pandemic, when the close quarters and primitive hygiene of WWI military life allowed the virus to mutate quickly among troops that then carried it home from the trenches. Eventually, that strain of H1N1 killed 3-6% of the global population. That kind of disbursal is still a great danger. For example, part of the worry about the as-yet unnamed SARS-like virus in the Middle East – one international committee proposed the name Middle East respiratory syndrome coronavirus or MERS-CoV – is that it’s concentrated in Saudi Arabia, home to Mecca and other Islamic pilgrimage sites. That means if MERS becomes more aggressive like its cousin SARS it could disperse regionally or globally via the Hajj.

Plague Inc. Screen 01

Plague Inc. also depicts human response efforts to fight pandemics. Most of these measures are mechanical translations of CDC and WHO measures to halt the spread of disease. Culling birds or livestock for instance, or distributing facemasks. Other measures involve shutting ports or recommending people practice social distancing. Public health countermeasures like these are an active part of life in many parts of the world, including the United States – during 2009 when the WHO issued a pandemic alert for Swine Flu, many businesses in the U.S. quietly developed contingency plans that would allow employees to work remotely from home. Hong Kong, which developed a societal paranoia of contamination after the SARS outbreak, is currently quarantining anyone who returns from the Chinese mainland with H7N9 symptoms. (Hong Kong is extreme. Even when there’s no threat of an epidemic, buildings sterilize their elevator buttons up to six times a day.) Island nations like Madagascar, Greenland, Iceland and Papua New Guinea also have geographical defenses by their natural separation, meaning that shutting down travel in or out of the country can be an effective barrier against pandemics – much to the frustration of certain Escapist editors. It’s a realistic portrayal. During the 1918 flu pandemic the U.S. Navy issued a total quarantine order for American Samoa, closing its ports. As a result, the territory escaped without a single infection. Western Samoa, on the other hand, kept its port open – and lost twenty percent of its population.

That’s a terrible blow, but note that it killed twenty percent, not one hundred. And that’s the behind-the-scenes secret to Plague Inc.‘s design: it’s weighted in favor of the contagion. In order to make the game playable – and winnable – Vaughan had to take liberties for the sake of game balance and that includes some pretty major assumptions. The first of these is that the disease can infect humans in the first place – a major stumbling block. The next assumption is the player. Having a human intelligence controlling the disease means that the illness reacts to changing conditions much more nimbly than random mutations would.

For example, if your plague isn’t taking hold in Russia players can start buying up cold immunity, whereas a real pathogen would just have to roll the genetic dice. Human agency allows a virus or fungus to not only adapt but to strategize and plan for the future, boosting its immunities to medication or jumping to rats while the world’s scientists are still chasing livestock.

Likewise, the maladies in Plague Inc. do something completely impossible for real-life diseases: simultaneous mutation. If you purchase the coughing symptom for your virus, the game doesn’t start a new mutant strain that carries on parallel to the new strain; instead all patients across the globe suddenly develop a cough. That would be like a baby being born with eleven fingers spontaneously causing the whole human race to sprout an extra pinky as well. “The concept of ‘simultaneous mutation’ is one area which gives the player a big advantage,” owns Vaughan, and it’s one of many “gameplay sacrifices,” that need to be made in order for the game to appeal to a wider audience.

These sacrifices also include making diseases advance through a population faster than normal. “In order to be an entertaining game, I couldn’t have people waiting around for years before anything big happened so I had to accelerate some things,” he says. “Also note that the human race is 100% susceptible to the disease – in Plague Inc., no one has natural immunity, no one recovers from the disease, no one survives!” During real pandemics, groups of people will be genetically immune from infection or recover faster than others. Much of the social strain during the Black Plague stemmed from the fact that the disease seemed so random and there was no detectible pattern of death – meaning people considered the plague a divine punishment that killed some and spared others. The result was everything from witch hunts to something far more cataclysmic: seeing two of his closest friends die influenced Martin Luther’s decision to join the Catholic Church.

In fact, while the game’s primary rhetorical purpose is to give the player a sense of human vulnerability, Vaughan’s research revealed something surprising: humanity’s extreme durability as a species. While pandemics in the past have killed millions of people, and there’s always another waiting at the door, it’s almost impossible for a single disease to wipe out all of humanity. Discarding our scientific defenses, our vaccines and N95 masks and sterilization, it’s our genetic diversity – our strength in difference – that actually protects us as a species.

In the end, we survive because we’re as unique and ever-changing as the pathogens that assault us.

Robert Rath is a freelance writer, novelist, and researcher based in Austin, Texas. You can follow his exploits at or on Twitter at @RobWritesPulp.

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