Corrupted Blood Incident
The Corrupted Blood Incident was an accidental virtual plague inside World of Warcraft during September 2005, when a raid boss debuff meant for one dungeon leaked out into the wider game and killed thousands of low level characters over roughly a week. The outbreak later became a serious case study for epidemiologists modeling how real people behave during pandemics.
Overview
The Corrupted Blood Incident was an unintentional in-game plague that swept through Blizzard's MMORPG World of Warcraft starting September 13th, 20052. A boss mechanic that was supposed to stay inside one raid dungeon escaped into the game's crowded capital cities, killed weaker player characters within seconds, and forced Blizzard to fight the outbreak with hotfixes and server resets over roughly a week1. Scientists later took the whole thing seriously as a natural experiment for how real people behave during an epidemic3.