Corrupted Blood Incident: When Game Glitches End in a Virtual Plague


Usually a glitch or another kind of issue in software is not affecting the user experience significantly. In the best-case scenario, the software version is also thoroughly tested and there were no bugs, to begin with. Sometimes however there is an overlooked aspect to a new feature or to new content of another type. When users don’t do what the developers would think they would do or by pure coincidence there can be issues that affect the overall experience significantly. One such glitch was the Corrupted Blood incident in World of Warcraft that not only disturbed the players but also got attention by leading epidemiologists and anti-terrorism officials.

What Is World of Warcraft?

World of Warcraft is a massively multiplayer online role-playing game (MMORPG) that was launched in 2004 by Blizzard and still dominates the MMORPG market heavily. Players are creating their own customized character to quest through the fantasy world of Warcraft which has been around since the first real-time strategy Warcraft game in 1994.


How did the plague start?

The virtual plague took place in September 2005 and lasted for a week. As part of a newly introduced world area Blizzard added a computer-controlled boss creature called “Hakkar, the Soulflayer”. This enemy would engage in combat with human players and curse them with a spell called “Corrupted Blood”. This spell was draining health from players rapidly but it was designed to only last a few seconds and should only be functional within this new area but one aspect was overlooked in the development.

How Could It Spread?

A bug was responsible for allowing the Corrupted Blood effect to be placed also on player pets and minions, which were not affected by it’s effect but could infect other human players beyond the zone it was designed for. Players were accidentally passing on the plague to others which was especially critical in crowded game cities where players meet – some players even passed the plague on to others intentionally.

How Did the Users React?

The spreading of the plague quickly killed low-level characters, of players who were new to the game, and annoyed the veteran players because they kept getting infected and yet again passing on the plague to others involuntarily. The spreading changed the normal game-play drastically, like no virtual event ever before in a game.Players avoided cities and tried to stay away from other human players as good as possible to avoid being infected and dying from it.

While death in the game is not permanent, it is yet frustrating and disadvantageous. It was however reported that player were trying to avoid the plague like if it meant an actual threat to their human well-being.


As grim as it may sound, some players even planned virtual biological attacks on their in-game human enemies and executed those plans infecting new world areas. Many others avoided the plague by simply not playing the game anymore, which would have led to a strong decrease in paying subscribers if not fixed by Blizzard.

Other players organized user imposed quarantine zones and those who had the abilities, also offered their healing services, trying to overcome the plague. Only after a short time the major cities were abandoned and all that was left were masses of corpses and skeletons from player who died there from the plague’s effects.

How Was the Plague Ended?

There has been attempts of programmers to impose quarantines and advising the players on what they should do to avoid spreading the plague further but all these strategies including the goodwill and common sense of players were fruitless.

The only way to end the plague were a combination of software patches along with several resets of the virtual world. This could be considered the worst outcome if compared to a real plague, as this is not a solution that could have been implemented in the real world.

Reactions in the Real World

While video games and the player’s interactions are usually not in scope of many scientific researches nor for official governments to assess, the Corrupted Blood incident was very thoroughly analyzed by epidemiologists as well by anti-terrorism officials.

In March 2007, Ran D Balicer, epidemiologist physician from the Ben-Gurion University of the Negev in Beersheba, Israel, published an article about the similarities between the virtual Corrupted Blood outbreak and real-world diseases like SARS and avian influenza. Dr Balicer pointed out that such online games could serve as an advanced platform for modeling the dissemination of infectious diseases.

“The main strength is that World of Warcraft involves ‘real’ people making real decisions in a world with some kind of controllable bounds. To put it academically, you have both dependent and independent variables.”
– Charles P. Blair

Charles Blair, deputy director of the Center of Terrorism and Intelligence Studies, confirmed that there could be value in analyzing player behaviour for terroristic behaviour and assess how fast even normal users learn what they need to do to cause the highest damage to a group of people as large as possible. While not all academics and specialists agreed to Blair’s angle, there might still be some truth to it.


Yes, World of Warcraft is a video game and entirely virtual with an environment that screams “fun and fantasy”. Death is not permanent and in-game events are irrelevant to a player’s real life. While this is all true and correct, we cannot deny that even in an immersive virtual environment such an event can bring out the best in humans and the worst alike.

The Corrupted Blood incident happened almost 10 years ago and still it holds a certain relevance in studies about virtual human behavior and how it could possibly compare with the behaviour of people in the real world.

Also a strong emphasis here lies on the fact that it was not possible to control the plague and cure it based on the cooperation of players. Whether they did not care to listen or did not understand what they had to do is irrelevant for the outcome – they kept on spreading the plague and only external machine resets and software patches helped “cure” the plague.

This is behaviour that could be also applicable in the real world with a real epidemic disease and that’s the fascinating thing we learn from the Corrupted Blood incident and can  hopefully account for such a behavioural pattern if we are to ever face such problems in the real world.

YouTube: Dawn of Death – Corrupted Blood (With Sound)

Source: Wikipedia
Photo credit: WikiMedia / Blizzard

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Christopher Isak
Christopher Isak
Hi there and thanks for reading my article! I'm Chris the founder of TechAcute. I write about technology news and share experiences from my life in the enterprise world. Drop by on Twitter and say 'hi' sometime. ;)
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