On September 13, 2005, Blizzard's incredibly popular massive multiplayer online role playing game wow classic gold (WoW) experienced an event that mimicked the spread of a viral infection throughout its playerbase. A damaging effect, called Corrupted Blood, ravaged thousands of gamers, and abandoned lower-leveled personalities in an inevitable death-loop. The effect, called a debuff, was a temporary condition, but one that may spread to other gamers if they stood close enough to one another, just like a true virus.

A week following the outbreak, it forced Blizzard to restart every WoW machine to stop it from spreading out of control.

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Hakkar would cast Corrupted Blood on gamers and it might damage them for about 10 minutes. Players would spread the effect to others if they got too near those infected. After the 10 seconds were done, or players finished the boss battle, the harmful impact was supposed to finish. Only it didn't.

A programming oversight allowed the debuff to disperse beyond the site of this Hakkar boss fight and to the world at large. Much like rats fueled the Bubonic Plague, characters' trained creatures lacked the Corrupted Blood outbreak. Hunter characters may summon and dismiss pets to fight in their side at will. Once dismissed, all of the effects on the pets are paused until it is called back out again. In effect, the pets could contract Corrupted Blood through the boss fight, vanish and then display the symptoms elsewhere in the world map if they were again summoned. There it would spread to buy classic gold wow other players and pets which came in contact with them.