They'll have to make the illness immune to common spells such as "Cure Disease"
For all you nerds out there, a pair of disease researchers are seriously looking into using massively multiplayer online gaming environments to study the spread and control of epidemic diseases. The researchers are already talking with Blizzard to use their World of Warcraft environment to run the tests. They plan to unleash carefully designed diseases into the world to infect player characters and let them interact realistically with each other to simulate a real life disease.
People had been thinking about using World of Warcraft or other online communities like Second Life for disease research since the infamous high-level Warcraft disease that got out of hand, temporarily wreaking havoc on several servers. These researchers look to go ahead with the promise of that unplanned outbreak with research of their own.