paxamericana:

The epidemic began on September 13, 2005, when Blizzard introduced a new raid called Zul’Gurub into the game as part of a new update. Its end boss, Hakkar, could affect players by using a debuff called Corrupted Blood, a disease that damages players over time, this one specifically doing significant damage. The disease could be passed on between any nearby characters, and would kill characters with lower levels in a few seconds, while higher level characters could keep themselves alive. It would disappear as time passed or when the character died. Due to a programming error, players’ pets and minions carried the disease out of the raid.

Non-player characters could contract the disease but were asymptomatic to it and could spread it to others.[2] At least three of the game’s servers were affected. The difficulty in killing Hakkar may have limited the spread of the disease. Discussion forum posters described seeing hundreds of bodies lying in the streets of the towns and cities. Deaths in World of Warcraft are not permanent, as characters are resurrected shortly afterward.[3] However, dying in such a way is disadvantageous to the player’s character and incurs inconvenience.[4]

During the epidemic, normal gameplay was disrupted. Player responses varied but resembled real-world behaviors. Some characters with healing abilities volunteered their services, some lower-level characters who could not help would direct people away from infected areas, some characters would flee to uninfected areas, and some characters attempted to spread the disease to others.[2] Players in the game reacted to the disease as if there was real risk to their well-being.[5] Blizzard Entertainment attempted to institute a voluntary quarantine to stem the disease, but it failed, as some players didn’t take it seriously, while others took advantage of the pandemonium.[2] Despite certain security measures, players overcame them by giving the disease to summonable pets.[6] Blizzard was forced to fix the problem by instituting hard resets of the servers and applying quick fixes.[3]

The major towns and cities were abandoned by the population as panic set in and players rushed to evacuate to the relative safety of the countryside, leaving urban areas filled to the brim with corpses, and the city streets literally white with the bones of the dead.[7]