Corrupted Blood Incident

Work in progress :)

World of Warcraft (WoW) is a massively multiplayer online role-playing game (MMORPG) released in 2004 by Blizzard Entertainment. Corrupted Blood was a virtual epidemic in the World of Warcraft an it began on 13 September 2005, when Blizzard introduced a new raid called Zul'Gurub.

Problem definition

The Corrupted Blood original debuff informations. Debuff was changed many times during early phases of inicent.

Outbreak originated in the new dungeon Zul'Gurub and since then it is known as the "Corrupted Blood incident. Dungeon boss Hakkar was a blood god also known as the Soulflayer, who had, among his arsenal of weapons, a "debuff" spell called "Corrupted Blood." Infected players would suffer damage at regular repeating intervals, draining away their health. Debuff also damaged other near by players and rapidly spread. It was unintentionally released into the larger game world and became the first disease to affect entire servers.

The "Corrupted Blood incident" was not intentional. The biggest factor in the rapid spread of the disease was a glitch in the programming. Non-playable companions of players could became infected and could carry debuff out of the dungeon. This turned them into asymptomatic carriers and a form of vector for the debuff. As Corrupted Blood infection spread uncontrollably. During the epidemic capital cities were abandoned as players rushed to evacuate to the relative safety of the countryside, leaving urban areas filled with dead player characters.

Blizzard had to fix the problem by applying hot fixes, patches and multiple hard resets of the servers. The plague ended on 8 October 2005, when Blizzard made pets unable to be affected by Corrupted Blood debuff. Debuff could not get outside of Zul'Gurub. The incident has helped many scientists model real-life epidemics since they would be able to draw on hard data showing how players actually responded during an outbreak.

Game vs. real-life

Unlike real life, the World of Warcraft virtual environment is specific in many ways. Among the main differences important for simulating the spread of the debuff epidemic are the following:

• Unlike any other real-life disease, debuff has an extremely high infectivity, spreading to all players in the spread range.
• Debuff also has a very rapid course. Players with low levels or health can be killed instantly. Players with higher levels can survive a certain duration of the debuff.
• Players have a defined amount of health (HP). If their health drops to zero they are moved to the graveyard in the form of a spirit. The spirit cannot interact with the environment or use action abilities.
• Death is not permanent. If a ghost player reaches the place of his death he can revive with a certain amount of health.
• A player character can have a "healer" class. Healers can use their abilities to increase the health of injured players or remove debuff.

Method

The NetLogo program was used to develop the simulation. NetLogo is used for agent simulations. In this case, the reactive agents represent player characters in capital city.

Model

The model represents a simplified environment of the capital. In the capital, players perform a huge number of interactions with the environment (using mailboxes, completing quests, auctions, logging into arenas and battlegrounds, improving their professions, using travel hubs and portals to travel to other cities, etc.). Due to the number of "objects" that could be the target of players' movement, the objects are not directly present in the environment and the movement is simplified as a route to random targets on the map.

The model is quite adjustable using the switches on the Interface screen. The user can choose the following parameters:

• Number of players present
• Number of infected players at the beginning of the simulation
• The percentage chance that a player's character is a healer
• Whether healthy players should avoid being infected
• Whether infected players should distance themselves from other players
• Whether players should revive after a certain time
• The health threshold at which healers heal players rather than remove the Corrupted Blood debuff
• Set the percentage chance of making a mistake (distancing / avoiding)
• Whether healers should have specific classes with specific abilities and healing style

The simulation is set up with the Setup button and started with the Go button.