When we think of pandemics, we think of the Black Death, yellow fever, typhoid, or, in more recent times, the flu. Each one of these shares a few common traits. They start off from a single source and then spread from person to person. The contagion spreads rapidly until most areas around the world are affected.

Just ask anyone who played World of Warcraft in the fall of 2005.

With millions of players around the world — the real world, that is — World of Warcraft is easily one of the biggest successes in computer gaming history. Players control avatars in the fictional world of Azeroth, fighting off monsters while improving these characters at the same time. Players also receive quests, typically from in-game guides (“non-player characters,” for those familiar with the lingo), and completing a quest typically yields their characters a reward — and often involves defeating an enemy with a special, sometimes unique trait.

On September 13, 2005, Blizzard — the makers of World of Warcraft — released an update to the game. The update contained a new dungeon and with it, a new quest, which culminated in an assault on a boss named Hakkar. When characters attacked Hakkar, he cast a spell on them called “Corrupted Blood” which slowly drained the life of anyone so inflicted. Corrupted Blood was designed to be contagious — anyone coming into contact with anyone infected with it would, in turn, also become infected. However, it was designed to only last a few seconds and, importantly, only have an effect within the dungeon containing Hakkar.

Before encountering Hakkar, players did not know exactly how the Corrupted Blood spell worked — intended or otherwise. Those who suddenly found their character’s health falling did what anyone would do: they ran away. Some even teleported out of the dungeon, expecting to find safety in town. And if Corrupted Blood had worked as it was designed, these characters would have been magically cured upon their successful exit from the dungeon. Unfortunately, the spell did not work as designed. The characters remained infected and, even worse, began to spread the disease to unsuspecting characters near them. Corrupted Blood began to spread throughout the area.

Even though a character’s death in World of Warcraft is not permanent, players still reacted as if it were a big deal. Many fled cities, realizing that the high population density was a death sentence. Others helped direct the uninfected to safe areas. And many of those with high level healing powers tried (in vain) to stave off the spread of the disease. (And of course, virtual versions of Typhoid Marys helped spread the curse — intentionally.) In fact, real-life health officials have studied the Corrupted Blood plague as a model for pandemic reactions by actual, flesh-and-blood people.

As for the virtual plague? At first, Blizzard tried to fight it in the same manner that their real world counterparts would have, issuing quarantine orders — while hoping to correct the programming bug at the same time. But when this failed, Blizzard pulled out an option not available to those of us outside of Azeroth. They reset the servers and restarted with a new, fixed version.

Bonus fact : Google uses search volume to help fight the flu. The company has put together a flu-tracking map, available here, which hopes to catch an increase in flu outbreaks before they become epidemics.

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