It’s 2005. Players anxiously prepare as they enter the World of Warcraft raid dungeon for the first time. They manage to find their way to the end boss when they are hit by a debuff (a negative status effect in role playing games that disappears over time) that had never been seen before- Corrupted Blood.
Corrupted Blood did a massive amount of damage and was transferrable to nearby characters, including pets (a companion available to certain classes of characters that was able to be summoned to assist the character.) What they didn’t know was due to programming oversight, a player could “dismiss” their pet while it was infected and when it was called back, it would still have the debuff active, rendering it a particularly dangerous biological weapon, especially in large, crowded cities. Also unknown to the players was that non-player characters (NPCs) could be asymptomatic carriers, where they are infected, but not affected by the debuff, allowing for even further infection.
Urban areas were emptied as players fled to the countryside, where there was a sense of safety. Cities were filled with the bodies of fallen players, the streets “literally white with the bones of the dead,” one player stated.
This became the first digital plague, which lasted for almost a month. It was patched after a series of hotfixes and hard resets on the servers, but it also provided valuable information to epidemiologists as it gave insight on real-world responses to an epidemic.
There were players that would try to heal those affected long enough to wait out the effects of the debuff, low-level players who were limited in skills would divert players from infected areas, however there were players who were would knowingly spread the disease, purposefully summoning their infected pet into quarantined areas, spreading the disease further.
The Corrupted Blood incident has been compared to avian flu, in the sense that the hosts were both animal and human, was passed through close contact, and there were characters who would contract it, but were asymptomatic, in this case, non-player characters.