We live in a germy world, says William Schaffner, infectious-disease specialist and chairman of the Department of Preventive Medicine at the Vanderbilt University School of Medicine in Nashville, Tenn. “If we went down to Times Square and began culturing people’s noses, something like 10% to 20% of them carry the antibiotic-resistant staph infection MRSA,” he adds.

For the most part, however, those bacteria are harmless since we all have immunities against them. Simple hygiene—showering, washing hands—”will keep the bad guys at bay,” he says.

Same goes for the barefoot march through airport security. The risk of catching athlete’s foot or another fungus from fellow travelers is very low.

“It’s in prolonged dampness that a toe fungus can get a foothold, so to speak,” says Dr. Schaffner. “So unless you’re in the middle of a monsoon and the airport has flooded, you’re not going to be sloshing through a sea of water and spreading foot germs.” Even in the humid month of August, when sweaty feet traipse through airport security, the area is essentially a dry environment.

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