Modeling Epidemic Spread in Synthetic Populations: Virtual Plagues in Massively Multiplayer Online Games

This paper examines virtual plagues, behavior-affecting properties that spread among characters in Massively Multiplayer Online Games, and argues that epidemiological tools and theory can be usefully applied to recognize, monitor, and control them. The authors treat the MMOG population as a synthetic population and the game itself as an interactive executable model of disease spread. Their aim is to understand the properties of virtual plagues rather than to eliminate them, since the effects of such plagues need not be unwanted and the mapping to real-world disease is not constraining for the initiators, who are often players, modders, or developers seeking entertainment.

The authors review notable historical cases, including the guinea pig mod in The Sims, the Corrupted Blood debuff in World of Warcraft, and the Gray Plague in Kingdom of Loathing, to illustrate how virtual plagues evolve through initial, epidemic, and recovery phases. They argue that classical macro models such as the SIR framework, which rely on homogeneous mixing and aggregate parameters like the basic reproductive rate, are poorly suited to virtual plagues. Micro-simulation approaches with explicit agents, spatial representation, and heterogeneous individuals are presented as the more adequate alternative, because virtual spread depends on in-game geography, chat and messaging channels, player heterogeneity, and risk attitudes that differ from those in real life.

The paper is primarily conceptual and qualitative rather than empirical, and it draws on game-specific anecdotes, community reports, and a sketch of a microsimulation model for a synthetic population of 2000 individuals. It offers guidelines for designing and controlling virtual plagues and concludes that micromodeling is currently the only adequate approach, while noting that the field remains in its infancy and that access to game data would enable more systematic study across different MMOGs.