Jan Woitas / EPA Twenty-four players test a demo version of the computer game Starcraft 2.

Who says video games are a waste of time? World of Warcraft  a virtual online world where millions of players quest for power, wealth and magical items  has got public-health experts considering new ways to track the spread of disease.

That's the message behind a new paper appearing this month in the journal Lancet Infectious Diseases, and also behind a separate, similar paper published in Epidemiology earlier this year. Both papers document the path of an unexpectedly virulent virtual disease called "Corrupted Blood," which swept through World of Warcraft's online characters starting in September 2005. (The game's administrators introduced the disease as a challenge for some high-level players; they didn't expect it to break out of the caves and into the virtual world's cities and towns.) The disease then ravaged the player population  despite administrators' efforts to quarantine the infected  and gave World of Warcraft its first virtual-world pandemic.

In real life, epidemiologists have long used complex mathematical models to predict how an outbreak of, say, pandemic flu might spread around the world. The problem is that testing those models isn't very easy, which makes it hard to judge whether the models are accurate. Scientists can't just release pathogens into cities and see how many people die. So, instead, they base their models on past outbreaks, where information collection was imperfect, or on people's stated (but hypothetical) beliefs about what they would do during a future outbreak. The resulting models can be remarkably sophisticated, but they "lack the variability and unexpected outcomes that arise ... not by the nature of the disease, but by the nature of the hosts it infects," according to Eric Lofgren and Nina Fefferman, authors of the Lancet Infectious Diseases paper. For example, they say, the failure of the World of Warcraft quarantine "could not have been accurately predicted by numerical methods alone, since it was driven by human decisions and behavioral choices." In other words, no model will know whether or not people ignore infection-control rules in the real world.

Lofgren and Fefferman  along with Ran Balicer, who wrote the Epidemiology paper  hope that virtual worlds will offer a chance to study that human variability. A few features of World of Warcraft made the game's 2005 outbreak a surprisingly good simulation of a real-world epidemic, they suggest. Players could teleport from one virtual-world location to another (not unlike hopping a transcontinental flight in the real world) and players kept pets, which got infected, serving as reservoirs for the disease. In response, some players with healing powers then traveled to help heal the sick, just as medical staff would be dispatched during a real-life epidemic.

Virtual-world characters aren't a perfect mirror of human society, of course. It's probably safe to assume that 20-year-old suburban males are overrepresented among World of Warcraft players and that teen mothers from Cambodia are underrepresented. We might also assume that players become more daring with the health of their online orc-slaying adventurers than they would be with their own health; in real life, death can be kind of a big deal.

But Lofgren and Fefferman believe a virtual disease could be devised to prompt a "reasonable analogue" of some real-world human responses  or at least give some sense of scale of the impact that human variation is likely to have. Games also have a couple of distinct advantages over real-world studies. Researchers can have a perfect understanding of the parameters of the disease and capture every person's response exactly, without any lost information. "Human response is, almost by definition, difficult to predict," Lofgren and Fefferman write. Virtual worlds may not be perfect, but perhaps they can eliminate some of the guesswork.