As Ebola rages, the case for prohibiting travel from West Africa

A sign asks patients to inform staff if they have fever, cough, trouble breathing, rash, vomiting or diarrhea symptoms and have recently traveled internationally or have had contact with someone who recently traveled internationally at Bellevue Hospital in Manhattan.REUTERS

On Wednesday, federal health officials announced that they would soon begin fever screenings at five major U.S. airports of all passengers arriving from Liberia, Sierra Leone, and Guinea, the three countries hardest hit by the raging Ebola epidemic.

The fever screenings are the first widespread, Ebola-related restriction placed on travel into the United States, and they come three weeks after Liberian national Thomas Eric Duncan landed in Dallas and became the first person to unknowingly bring the disease here. The idea of screening every disembarking passenger from three countries is a dramatic change to the normal free flow of international travel. But according to the head of a research institute in Cambridge, the new restrictions might still not go far enough.

Yaneer Bar-Yam leads the New England Complex Systems Institute, and for years he’s been arguing that in cases of severe infectious disease outbreaks, the best policy might be to prohibit travel from afflicted countries altogether.

“At the global level, I do think transportation should be curtailed from, but not to, West Africa,” he says.

Bar-Yam is trained as a physicist. His research primarily focuses on the behavior of complex systems, like, for example, the way an infectious disease moves through a population. In 2006 he coauthored a paper with Erik Rauch, a computer scientist at MIT, called “Long-range interactions and evolutionary stability in a predator-prey system.” The title is a mouthful, but the paper’s implications for the current Ebola outbreak are stark. Bar-Yam and Rauch used mathematical models to simulate the spread of an infectious disease; their analysis suggests that even small amounts of travel between regional populations may be enough to allow an infectious disease to jump from one country to another. “Even if significant mixing already exists,” the authors write, “a small amount of additional mixing may cause extinction.” And in this case, extinction means us.

Bar-Yam doesn’t actually think Ebola poses a threat to all of humanity, but he does think that an embargo on travel from the most heavily affected nations might be necessary to contain the disease. He supports this analysis in terms that are especially disquieting for citizens of countries where Ebola is already present. “Severe pathogens . . . can be stopped by the very fact that they’re destructive,” he says. “If they kill off their host, whatever’s going to happen is going to happen locally.” In other words, epidemics burn out on their own when the disease has no one left to infect, provided they’re not able to hop across oceans on airplanes.