Purpose: The degree and pattern of spread of an infectious disease such as influenza may depend on many social, cultural, and geographic factors. We developed a model of a hypothetical spread of avian influenza in Norfolk, Virginia.

Methods: We constructed an influenza model using BioWar, an agent-based computer model that uses census, geographic, school district, social network, and sociological data to simulate the daily activities and interactions of an entire city and its population at 20% scale. Our model simulated the hypothetical spread of influenza through Norfolk, Virginia, whose metropolitan statistical areas (MSA) has a population of 1.530908 million (including 396,953 children, 973,716 actively employed individuals) and 346 schools, during a time frame of one year from July 1, 2002 to June 30, 2003. On November 28, 2002, 200 cases of influenza were introduced into the population. It was assumed that no one in the population had any initial immunity to this strain of influenza and after recovering from infection developed full immunity. Influenza characteristics (transmission probabilities, prodromal and infectious period lengths, and mortality) were based on a combination of reported values from the literature and expert opinion.

Results: Figure 1 shows the number of active cases of influenza over time with a peak of 157,170 cases on March 12, 2003. The shape and peak of this curve could be replicated by a susceptibles-exposed-infectives-recovered (SEIR) model. A peak of 5,190 health care workers (March 11, 2002) were afflicted with influenza. Daily emergency room visits and clinic visits for influenza reached maximums of 82,150 and 26,440, respectively. Daily school absences peaked at 8,730.

Conclusion: Using BioWar, our agent-based city-wide computer simulation model predicts the various effects that the hypothetical spread of avian influenza could have on Norfolk, Virginia.