The Corrupted Blood Incident


It was September 13th 2005 when the disease first began to spread, hopping from animal hosts into their owners and from there into the shop-keeps and other civilians. It came out of nowhere, no one could have expected something like this, there simply was no precedent.

The disease was known to appear deep in the jungles of the vale, places where few mortal men dare to tread, but when it began to appear on entirely different continents, the world knew that this wasn't just some curse inflicted on those who dared tempt the wrath of a forgotten blood god, it was a pandemic

From Ironforge to Orgrimmar, the nations of the Horde and the Alliance would face this global threat in what is now known as the Corrupted Blood Incident

Episode: File 0018: Corrupted Paralysis Cure-Alls

Release Date: March 12th 2021

Researched and presented by Cayla

Yes, we're talking about a video game. In 2005 World of Warcraft (WoW) had over 2 million subscribers logging in to smite murlocs and fight great evils together. Even if its popularity has faded somewhat 15 years later it's still going strong at 5 million subscribers today and will likely continue to be a fixture in the gaming world for a long time to come

So what happened? I wasn't lying, there was a pandemic, it traveled the globe of Azeroth and infected player and NPC alike. But where did it come from?

September 13th was a Tuesday and anyone that has drank from the Blizzard kool-aid of warcrack knows that Tuesdays are patch days and when new content is added.

This patch day Blizzard released a brand new raid called Zul'Gurub. Raids are what you did when you maxed out the level of your character and had time to burn. Guilds (groups of players) would form balanced teams to tackle these raids and fight the multitude of bosses inside for a shot at the best gear in the game. And then do it all again the following week. It took determination, coordination and time. Oh so much time.

Prior to Covid when was the last time you could get a couple people to get together for something? How about getting 20 people online at the same time, all skilled and geared enough to be worthy of their spot, willing to show up multiple nights a week for hours at a time? But really this was a nice change from the previous raids which required 40 players

My regrets about my wasted youth aside, a new raid was always exciting and guilds often prepared for weeks before a patch would drop to rush in and try to be the first to beat it to earn themselves the elusive world first achievement

This enthusiasm is also what made patch day also become day 1 of the infection

Within hours of the patch going live infections had spread across entire cities, the underground Dwarven city of Ironforge and the Orc city of Orgrimmar were the primary gathering hubs for the alliance and the horde. It was not uncommon to see hundreds of players just hanging out in these cities, waiting to meet up with friends, crafting, using the auction house or just AFKing. And the corrupted blood cut through them all like wildfire

The Zul'Gurub load screen
The Zul'Gurub load screen

How does a raid on southern most corner of nowhere spread disease to cities continents away? It was all thanks to man's best friend or demonic familiar

The final boss of the raid was Hakkar the Soulflayer. During combat, he would steal the player's life, drive them insane, taking control of their characters and, oh curse them with the bane of Corrupted Blood a debuff that would eat away at their life and pass itself on to anybody in proximity

The effect itself only lasted ten seconds, not nearly enough time for someone to make the arduous run out of the raid and to a nearby town or even hearth. But classes like Hunters and Warlocks have pets and pets like players can be infected with Corrupted Blood, but pets can be de-summoned, like tucking them away in your pocket. Typically anything that is going on with your pet will reset when you put it in your pocket, but somehow that logic didn't include the Corrupted Blood debuff

So if a player's pet did get infected and they did de-summon them before the effect ended, the next time the player would pull out their pet, the pet would still be infected and would immediately begin infecting players and pets within range. It's one thing if you summoned your pet while out doing quests alone, the infection would die out pretty quickly. But if this were to occur in areas where large numbers of players congregate? It could quickly turn into a disaster, which is exactly what happened

The first outbreaks were probably purely accidental, but as the word spread, there are those that saw an opportunity for shenanigans.

Soon the infection spread, whether it be accidental or intentional, instantly killing lower level players, or transferring from higher level players as they tried to escape. This event would change gameplay for that week in an unprecedented way

But it wasn't just the infected players to be feared, the infection also spread to NPCs, who didn't die from it for whatever reason, but became asymptomatic carriers which could then infect other players and NPCs

Since raiding required so much dedication and skill, getting to the last boss of a brand new raid wasn't something that just anyone could do, there likely was only a handful of guilds that were able to accomplish that on day 1.

Which meant, unless you were obsessively reading raiding and dungeon guides, the average player likely knew absolutely nothing about what corrupted blood was. Which probably was true of some 95% of the players. So suddenly players were dying in the cities and depending on your level and your gear it could happen in an instant and you wouldn't even know why.

The debuff
The debuff

You would make the run back to your body to resurrect, still baffled about what the fuck had just occurred, noticing now the bodies that were scattered everywhere. As you enter back into your physical form, you realize now that something's happening and then you're hit with it again

You're reading the general chat and among the Chuck Norris jokes and the trolls people were desperately trying to find out what was happening, well-meaning players urging others to run. So you get back to your body but now there is a death timer, preventing you from resurrecting again right away. So you wait, watching in your spirit form as players all around you continue to fall and spam *dance* emojis

You get back into you body and start booking it toward the entrance, but you're a new player, you haven't quite figured out the layout of the city and you only get a couple steps before you're re-infected and collapse again

On the right side of screen you see the little armor mannequin indicating with yellow and red that your gear is now damaged from dying. You make the body run, and now have to wait three minutes before you can come back. You spend this time, looking at the city map and still trying desperately to understand the situation

You get your chance, you get back into your body and manage to avoid infection for a couple beats, making some good strides toward the entrance, you don't see any players ahead, you might be scot-free, but you're afflicted again and as you collapse you see a city guard walk by

This continues, the death time maxing out at 6 minutes and as your gear all turns red rendering it useless your health and stats drop making death all the quicker with each piece crumbling to nothing.

You either give up and log off or after countless attempts finally break free of the city limits and you run off into the wilderness, putting a much distance between you and the city as you can. You think you have escaped it and you stop in a small town to repair your decimated gear. But you see that players have begun to congregate in the normally empty town and as you talk to the blacksmith you see the now familiar bloody icon indicating that you've been infected and you fall again

This is very likely what those first few days were like for the grand majority of the players. Players began to avoid normal congregation spots like cities and towns, evacuating them entirely, leaving only the NPCs and player corpses to instead seek more desolate corners of the world, while the programmers tried to impose quarantines and stop-gap measures until a permanent solution could be implemented.

Blizzard 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.

Some players simply stopped playing to avoid the hassle of and costs of repeated deaths

While dying is not permanent in World of Warcraft. It could get really costly, really quickly if you had any amount of higher level gear, especially in this era of the game. When a single death could cost you 1 gold in gear repairs and you only had 50 (if you were rich), you can see how this would be problematic

Sure the better geared players had a much better chance of survival, but if you can't escape infection, it doesn't matter how much health and gear you have, eventually you will die.

the difficulty of killing/reaching Hakkar likely played a factor in the spread of the infection, some gaming servers are more oriented to certain styles of play, with several of the top raiding guilds usually playing on the same servers. Three servers in total experienced a full blown pandemic, but it's likely that other servers experienced less dramatic contamination

Before Blizzard commented on the outbreak there was debate as to whether this was a glitch or actually intentional and part of a world event. Some saying this is the best "world event" Blizzard ever released, but it really was completely unintentional

The plague eventually ended on October 8, 2005, when Blizzard made pets immune to the infectious disease


Jeffrey Kaplan -a game designer for World of Warcraft-stated that it gave them ideas for possible real events in the future.

But it was also a potent reminder of how quickly something so small and spiral out of control

Brian Martin, an independent security consultant for World of Warcraft, commented that it presented an in-game dynamic that was not expected by players or Blizzard developers and that it reminds people that even in controlled online atmospheres, unexpected consequences can occur. He also compared it to a computer virus, stating that while it is not as serious, it also reminds people of the impact computer code can have on them, and they're not always safe, regardless of the precautions they take

Screenshot from the 2008 Wrath of the Lich King event
Screenshot from the 2008 Wrath of the Lich King event

In October 2008 a throwback was made when a zombie plague broke out for a week as a way to promote the new expansion Wrath of the Lich King. While inspired by Corrupted Blood, but unlike that incident the plague was a little better balanced

It was far less contagious, while Corrupted Blood had a 100% transmission rate, this plague was quite lower. When a player was infected, if they weren't cured they would eventually turn into a zombie, given new abilities to wreak havoc and attack other players, but ultimately short lived, lasting only a couple minutes before your character died

This meant encountering one or two zombies wasn't a big deal, but being overcome with a horde came with much higher risks of infection. But unlike Corrupted blood, many of the healing classes were able to cure the infected

The event received mixed reactions, much like every change that wow has ever experienced, some lauding their praise while otherwise criticized it, I personally enjoyed it

In 2018 the online card-game Hearthstone payed homage to the Corrupted Blood Incident

A card was released for Hakkar who could spread the card Corrupted Blood into yours and your opponents decks. Whenever the card would then get drawn, the player would take damage and then have to shuffle two more copies of the card back into their decks 

In 2019 As part of a special event, Hearthstone released a new card back called the Mark of Hakkar. This would replace the backs of all your cards with an animated version reminiscent of the old blood god. How did players get it? They simply had to play against a player that was using it.

Released on February 5th the card back had infected 87% of the playerbase within a 24 hour period, with one player even passing on the mark 63 times in that period. Only 200 players were given the card back to begin with 


Nothing like this had happened before and it created the perfect environment to observe human behavior in the midst of a simulated world pandemic, so naturally it attracted the attention of epidemiologists, eager to see what they could learn from such an event

Many scoffed at this, saying how could a video game provide any meaningful data for the study of real world pandemics? There's no way that people would behave the same way in a virtual environment as they would in a real life!

But surprisingly, player response did resemble real-world behaviors. Some characters with healing abilities volunteered their services to try and help people escape, lower level characters who couldn't help, stood outside infection zones and directed people away and some would just flee, leaving everyone else behind for their own safety. And of course there was the "griefers" those that thrived in the chaos and focused on only making things worse

Over years a variety of studies have been performed based on the data and information from this incident, here are some of them

March 2007: Ran D Balicer: An epidemiologist physician at the Ben-Gurion University of the Negev in Israel.

Published a paper noting the similarities between this event and the then-recent SARs and avian flu outbreaks. In it he suggested that RPGs could serve as an advanced platform for the modeling of infectious diseases. He later suggest that the game Second Life was another possible candidate for these studies

Balicer said the impact of teleportation in World of Warcraft was "similar to the role of air travel in the rapid global spread of severe acute respiratory syndrome (SARS)," while the havoc wrought by infected pets echoed the part played by asymptomatic ducks in spreading avian flu among bird populations

Centers for Disease Control and Prevention:

Contacted Blizzard for any data or statistics that they could provide on the epidemic, which Blizzard admitted they had little due to the fact it was a glitch

Games for Health Conference, in Baltimore

The corrupted blood incident has been cited as fascinating study of human behavior and can be compared quite easily to a real-life pandemic, in that the it originated in a remote, uninhabited region and was carried by travelers to larger regions; hosts were both human and animal, comparing it to the avian flu and was passed through close contact. And there people who could contract it but be asymptomatic (NPCs)

But there are elements that aren't as realistic such as the players being able to see when they have been infected and the effect the virus had was the same for all players.

One aspect the epidemic that researchers hadn't previously considered was human curiosity. Some players would rush into infected areas just to witness the infection and rush out. This was paralleled to real-world behavior, specifically with how journalists would cover an incident, and then leave the area.

August 2007: Nina Fefferman: Assistant Research Professor of Public Health and Family medicine at Tufts University

Co-authored a paper with Eric Lofgren, a graduate student from University of North Carolina, in Lancet Infectious Disease discussing the epidemiological and disease modeling implications of the outbreak

She spoke about the incident at the Games for Health Conferences in 2008 and 2011 and how massively multiplayer online populations could solve the problems inherent with more traditional models of epidemics.

The 3 base models that are used have their strengths and weaknesses but make significant behavioral assumptions. She also compared Corrupted Blood to a drug trial with mice-"a real good first step."

She spoke of ways this model could help push research forward, how different diseases with varying attributes, effects and lethality could be monitored to see how players reacted, how rumors spread and how awareness would disseminate through the player-base.

Blizzard had published notices during the outbreak, but she pointed out that they kept changing their position and the information was only useful if the players actually saw it. Many players didn't know what was happening until it was too late

She believes running these kinds of experiments in games like World of Warcraft could be a huge benefit to researchers and that they could be done in such a way as to not interrupt gameplay, and that it could even be fun if developers and researchers worked together

Initially Blizzard seemed excited about this idea, but their interest slowly waned, while they never outright rejected the idea, nothing came from it. Dr Fefferman has been in contact with other game developers in hopes of conducting similar simulations in other games

Blizzard has maintained a position that World of Warcraft is first and foremost a game, and that it was never designed to mirror reality or anything in the real world.

Neil Ferguson, director of the MRC Centre for Global Infectious Disease Analysis at Imperial College, London

Is skeptical of the idea, saying that such a study wouldn't properly mimic genuine behavior as the risk was low in a game, even if the characters died they could come back, thus limiting the usefulness of such studies

Model for Terrorism Research

Charles Blair deputy director of the Center of Terrorism and Intelligence Studies took something else away from the incident. He believed that WoW could be used to study how terrorist cells form and operate. His organization already uses computer models to study terrorist tactics, the use of an environment like WoW provided much better feedback in regards to human behavior and in a controlled environment


Last year, interest in the Corrupted Blood Incident made a surprise comeback. Epidemiologists who studied the original outbreak began to use the research they had done to better understand the spread of Covid, particularly the sociological factors

Dr Eric Lofgren who had worked with Nina Fefferman on her paper in 2007 made this comment to PC Gamer

"When people react to public health emergencies, how those reactions really shape the course of things. We often view epidemics as these things that sort of happen to people. There's a virus and it's doing things.

But really it's a virus that's spreading between people, and how people interact and behave and comply with authority figures, or don't, those are all very important things. And also that these things are very chaotic. You can't really predict 'oh yeah, everyone will quarantine. It'll be fine.' No, they won't."

One of the aspects that many researchers had dismissed from event was "griefing" , behaviour by players intended to cause chaos, like intentionally spreading Corrupted Blood to others. Researchers just couldn't see a real-world basis for such behavior

But Dr. Lofgen:

"one of the critiques we got from a lot of people, both gamers and scientists, was over this idea of griefing, ... How griefing isn't really analogous to anything that takes place in the real world. People aren't intentionally getting people sick. And they might not be intentionally getting people sick, but wilfully ignoring your potential to get people sick is pretty close to that. You start to see people like 'oh this isn't a big deal, I'm not going to change my behavior.' ... Epidemics are a social problem... Minimizing the seriousness of something is sort of real-world griefing."

Dr. Lofgren says. 

"If you think again in gaming terms, we're making saving throws against new emerging diseases all the time. And sometimes you fail... We have epidemics recur with some degree of frequency. It's sort of like getting rid of people who predict earthquakes because you haven't had an earthquake in awhile. Well, yeah, you're gonna have another one." 

Dr. Nina Fefferman, a co-author of the Corrupted Blood study, expressed that the incident particularly exemplified "how people perceive threats and how differences in that perception can change how they behave", and how people discuss a threat on social media, stating that 

"A lot of my work since then has been in trying to build models of the social construction of risk perception and I don't think I would have come to that as easily if I hadn't spent time thinking about the discussions WoW players had in real time about Corrupted Blood and how to act in the game based on the understanding they built from those discussions."

The equivalent to WoW players chatting about how to deal with the virus is now playing out across social media with Covid-19. Dr. Fefferman says that all her current work "focuses on how small decisions from individuals can lead to big changes for entire populations." She's studying how the age of patients and how they're tested is impacting our understanding of how Covid-19 is progressing