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Warcraft Plague: How a glitch inside "World Of Warcraft" did save lives

Warcraft Plague

Back in 2005, a very rare phenomenon happened: millions of people found themselves trapped in the clutches of a raging pandemic. Humans and animals were both affected. Cities were not safe anymore. Many fled away from highly populated areas to reduce of risk of being infected by the disease.

And believe it or not, all of this happened inside a video game.

World of Warcraft (WoW) is a huge online role-playing game set in the fantasy Warcraft universe. Created by Blizzard Entertainment in 2004, it is one of the highest-grossing video games of all time, with more than 100 million user accounts over its lifetime. Players control individual avatars who interact with each other, complete quests, and gain abilities and skills.

Unexpectedly, it was in this virtual world that epidemiologists and disaster planners discovered an untapped resource in trying to predict mass economic and societal responses to a global pandemic.

This incident was never meant to be an actual thing. Everything was a coding accident. A spell cast by “Hakkar The Soulflayer” was intended to deal damages during a boss fight. This spell could indeed be passed between players in close proximity. Though, due to “hunter pets and teleportation”, the debuff spread outside of the boss area. Just like a real virus it started infecting characters in cities and usually peaceful areas.


Corrupted Blood created mayhem throughout WoW. It would instantly kill new and weak avatars, which not only brought in thousands of complaints from players with dead characters, but also left piles of skeletons and corpses scattered throughout the cities and towns. Users had their characters leave the cities for more isolated areas, or stopped playing the game all together.

What was amazingly stunning is the behaviour of the players during the incident. Some tried to heal, and some tried to spread the virus. Blizzard even attempted to impose quarantines on players to contain the disease but these were not well received and in the end, Blizzard reset the servers and fixed the code.

The incident inspired researchers

After the incident, many papers were published inspired by the reaction of players during the pandemic. Searchers strongly pushed forward the use of video games to help study human behaviour.

Epidemiologist use complex mathematical models to predict the spread of infectious diseases. But this does not take into account the irrational behaviour that us humans are capable of. Moreover, it is simply impossible to test it in a real-world experiment.

So why not use virtual worlds to run social experiments?

Social experiments are expensive, require lots of time, effort and money. But one could easily replicate them in video games! Let’s offer a cheap and effective way to run social experiments for psychologists, epidemiologists, economists… and financially support small game development companies.

Who’s with me? :D