"In the past, one expected the spread of disease to be based on distance, and the closest town would be the location of the next outbreak," says Dr. Ottar Bjornstad, assistant professor of entomology and biology. "Today, it is very different. Even excluding air transportation, someone like me is more likely to go to New York City than Lewistown, Pa., even though Lewistown is closer to where I live."

Borrowing from physics and transportation theory, the researchers are using an empirical gravity model along with the distance-based models to define a network of spatial spread of contagious disease.

"We are combining the basic theory of epidemiology with models from sociology and transportation theory to see what networks might look like," Bjornstad told attendees today (Aug. 5) at the annual meeting of the Ecological Society of America. Bjornstad is working with Bryan T. Grenfell and Xia Yingcun, University of Cambridge, U.K.

Cities are like planets -- the larger they are, the more attractive they are, but the degree of attraction decreases with distance. From Central Pennsylvania, New York City or Philadelphia would be more an attractive destination than Chicago.

To test their model, the researchers used British data on the childhood disease measles because British records dating from 1940 to today are relatively complete. The records show, week-by-week and community-by-community, the spread of measles outbreaks. The U.K. has about 1,000 cities and 450 rural areas that report and outbreaks occur about every two years.

Measles belongs to an ecological class of disease that includes the traditional childhood illnesses mumps, rubella, chickenpox, whooping cough that are extremely contagious, but short-lived in t
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Contact: A'ndrea Elyse Messer
aem1@psu.edu
814-865-9481
Penn State
5-Aug-2004