The experiment's takeaway was this: When the perception of risk increases, the feeling of risk increases. This lesson is instructive in thinking about why some pockets of America are overreacting to the threat of Ebola.

The chances that Ebola will infect any given American is incredibly, incredibly small. There have been four infections in the United States since the first case was diagnosed here last month. On the Net, bad jokes abound about how low the chance of contracting Ebola is—jokes like "Americans are more likely to marry Rush Limbaugh than die of Ebola."

To our collective credit, the American people are thinking pretty calmly about the disease's threat. Just 24 percent of respondents to a recent Gallup Poll said they were worried about contracting Ebola. But for some communities who see themselves as being just a few degrees of separation away from Ebola, the threat has provoked panic. To extend the metaphor from the Michigan experiment, these communities are being sneezed on or are acting out of fear of being sneezed on.

Parents in Mississippi (a state that has not seen a case of Ebola) have pulled their children out of a middle school because the principal was recently in Africa. A school in Ohio closed for disinfection after Amber Vinson, a nurse who contracted the disease in Dallas, flew through Cleveland and made contact with a parent of a student. A Texas college has denied admission to students who come from Ebola-infected countries fearing they might bring the epidemic with them. Some conservative politicians are petitioning to close the southern border lest an Ebola-infected migrant stroll across it.

For these people, Ebola hits a psychological nerve, a base evolutionary reaction to recoil from the things that can cause us or our communities harm. And that reaction becomes stronger when the disease creeps closer. These psychological reactions happen on a gut level, and we aren't always aware they occur. It's important to recognize that even when the threat of Ebola seems to be growing closer to a community, it's probably further away than it appears.

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Brian Resnick is a former staff correspondent at National Journal and a former producer of The Atlantic's National channel. Connect Twitter