A plague carried around the world by travelers, pets and curious teen-agers may show that experts have not taken everything into account when planning for an outbreak of disease, researchers said on Monday.

Luckily, the world involved is an Internet game.

The outbreak of Corrupted Blood indicates that specialists trying to predict what the next pandemic will look like might make use of a real-world laboratory -- the culture of online gamers.

It really looked quite a bit like a real disease, Nina Fefferman of Princeton University, who worked on the report with her then-student Eric Lofgren, said in a telephone interview.

This includes stupid behavior, near-instant international travel and infection by pets.

The outbreak was an accidental consequence of a software challenge added to the World of Warcraft game in 2005, Fefferman and Lofgren report in the journal Lancet Infectious Diseases.

The virulent, contagious disease was introduced by maker Blizzard Entertainment Inc. of Irvine, California, as an extra challenge to high-level players. But, just as a real virus might spread, it was accidentally carried out of its virtual containment area.

Soon, the disease had spread to the densely populated capital cities of the fantasy world, causing high rates of mortality and, much more importantly, the social chaos that comes from a large-scale outbreak of deadly disease, Fefferman and Lofgren wrote.

When this accidental outbreak happened, players embraced it. Some thought it was really cool, Fefferman said.

The makers did not. They reset the computer game to eliminate the disease, wiping out any data that may have been collected.


But Lofgren, who played the game, alerted Fefferman, and they studied what they could.

Fefferman, a medical epidemiologist, immediately recognized human behaviors she had not ever factored in when creating computer models of disease outbreaks. For instance, what she calls the stupid factor.

Someone thinks, 'I'll just get close and get a quick look and it won't affect me,' she said.

Now that it has been pointed out to us, it is clear that it is going to be happening. There have been a lot of studies that looked at compliance with public health measures. But they have always been along the lines of what would happen if we put people into a quarantine zone -- will they stay? Fefferman added.

No one have ever looked at what would happen when people who are not in a quarantine zone get in and then leave.

She will now incorporate such behavior into her scenarios, and Fefferman is working with Blizzard to model disease outbreaks in other popular games.

With very large numbers of players (currently 6.5 million for World of Warcraft), these games provide a population where controlled outbreak simulations may be done seamlessly within the player experience, she wrote.

Fefferman noted that Ran Balicer of Ben-Gurion University of the Negev in Israel came to a similar conclusion in a paper published in the journal Epidemiology in March.

Experts agree the world is overdue for a pandemic of some sort of disease. The current No. 1 suspect is the H5N1 avian influenza virus, which has killed 194 out of 321 people infected since 2003.