Most people don’t associate jet bridges and moving walkways with swine flu. What really bothers us are airplanes: cramped, crowded aluminum tubes where a sneeze from across the aisle is enough to set off warning bells in our heads. In cultural mythology, airplanes are where superbugs are born and entire cabinfuls of passengers infected in a single trip — offloading hundreds of new carrier agents at journey’s end into vulnerable environments.
It turns out, though, that the likelihood of actually catching something on a plane is kind of low. You’d basically have to be sitting on top of someone to become infected by their germs. According to Aaron Carroll, co-author of Don’t Cross Your Eyes… They’ll Get Stuck That Way!, airplane manufacturers have more or less gotten air circulation onboard their products down to a science. Between drawing in clean, fresh air from outside the cabin and passing old air through high-quality filters designed to catch 99.999 percent of germs, the air inside a cabin is replaced some 20 times an hour — far more often than in office buildings or in houses, which exchange air every 12 and 5 times an hour, respectively.
Add to that the fact that each row of an aircraft’s air supply is recycled vertically rather than moving forward or backward through the cabin — meaning airborne germs that survive the filters come back to the same row rather than spreading to other passengers — and what you get is a system that’s pretty hard to beat.