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New computer modeling technique shows how airports are key in spreading contagion
Researchers have used network theory to model just how profoundly the 40 largest airports in the U.S. would influence the spread of highly infectious diseases, such as H1N1 or SARS, in the first days of an outbreak.
Honolulu International Airport, an air travel hub in the Pacific that links the West to Asia, would be a key jumping off point for a dangerous disease, said the researchers. The study, released by Massachusetts Institute of Technology researchers on July 23, said past public health crises, like the 2003 SARS outbreak, which spread to 37 countries and caused about 1,000 deaths, and the 2009 H1N1 flu pandemic that killed about 300,000 people worldwide, have heightened awareness that new viruses or bacteria could spread quickly across the globe, aided by air travel.
The researchers by MIT's Department of Civil and Environmental Engineering (CEE) one-ups the infection pattern modeling done by other researchers on the worldwide spread of disease by shifting the focus to the first fifteen days of an epidemic, determining how likely the 40 largest U.S. airports are to influence the spread of the disease originating in their home cities. The new approach, they said, could help determine appropriate measures for containing infection in specific geographic areas and aid public health officials in making decisions about the distribution of vaccinations or treatments in the earliest days of contagion.
"The results from our model are very different from those of a conventional model that relies on the random diffusion of travelers … [and] similar to the advective flow of fluids," says graduate student Christos Nicolaides, first author of a paper by the four MIT researchers that was published in the journal PLoS ONE. "The advective transport process relies on distinctive properties of the substance that's moving, as opposed to diffusion, which assumes a random flow. If you include diffusion only in the model, the biggest airport hubs in terms of traffic would be the most influential spreaders of disease. But that's not accurate."
In the model created by the researchers, Kennedy Airport was ranked first, followed by airports in Los Angeles, Honolulu, San Francisco, Newark, Chicago (O'Hare) and Washington (Dulles). Atlanta's Hartsfield-Jackson International Airport, ranked first in number of flights, ranks eighth in contagion influence, said the study. Boston's Logan International Airport ranks 15th.
Honolulu, with its connections to the far east, where some of the more virulent forms of influenza have originated, could play a role far larger than previously thought, according to the research. Honolulu airport gets only 30 percent as much air traffic as New York's Kennedy International Airport, but the researcher’s new model predicts that it is nearly as influential in terms of contagion, because of where it fits in the air transportation network.
"The study of spreading dynamics and human mobility, using tools of complex networks, can be applied to many different fields of study to improve predictive models," says Marta González, the Gilbert W. Winslow Career Development Assistant Professor of Civil and Environmental Engineering. "It's a relatively new but very robust approach. The incorporation of statistical physics methods to develop predictive models will likely have far-reaching effects for modeling in many applications."