It is like the scene in The Wizard of Oz where Dorothy, the Tin Man, and the Scarecrow are fretting about the dangers of “lions and tigers and bears, oh my!” when the actual dangers they will face include, instead, a witch, flowers, and monkeys. Media have been promoting fear of a series of infections in America over the last couple years — measles, hantavirus, Ebola, and, most recently, cyclospora — though these diseases are far from the most significant threats to Americans’ health.