In a bizarre case of art imitating life, players of the Blizzard Entertainment game World of Warcraft suddenly found themselves dying from a mysteriously rampant plague that ravaged their virtual world.

The plague began innocently enough. Blizzard introduced a new dungeon area in the world, intended to give high-level players a bit of a challenge. But when players reached the boss at the end of the dungeon, they got more than they bargained for -- and unknowingly took a little something back to town to share with their friends. The dungeon boss, called Hakkar the Soulflayer, cast a spell called Corrupted Blood. The powerful spell caused about 280 damage points to anyone it hit, and spread to other members of the attacking party as well. Such powerful spell attacks aren’t unusual in the World of Warcraft game world. But what happened next was just plain weird.

When infected adventurers returned to town at the end of their quest, they inadvertently passed along the Corrupted Blood infection to those nearby. In short order, the plague ravaged the population. Soon entire cities fell victim to the artificial disease. And while 280 damage points may be easy for a level-58 Night Elf warrior to contend with, it’s enough to kill a lower-level player in seconds.

Game administrators were baffled. As they scrambled to quarantine areas of the game world, the disease quickly spread beyond their control. Partially to blame was the game’s "hearthstone" feature, which allows players to essentially teleport from one area to another, and which made it possible for the plague to reach the most distant regions of the map in just minutes.

Eventually the game’s administrators came up with a "spell" to cure the plague and managed to distribute it to the players en masse. But the legacy of Corrupted Blood remains. While software viruses are nothing new, Corrupted Blood is unique in that it’s the first such infection ever to spread through a virtual environment without being deployed by malicious intent. It was, in a certain sense, naturally occuring in its environment. You might even say it evolved and sought self-propagation, just as any lifeform would do.

In the days since Blizzard eradicated the plague, the company has remained surprisingly quiet about what happened. But you can still find plenty of players willing to talk about it. One 14-year-old Orc told me openly of the incident: "Humans were dying left and right. We just laughed and laughed."