There is no more powerful image of fear than a population gripped by plague. A novel flu virus exploded through Mexico last week, killing some 150, infecting hundreds more, and generating images of masked citizens and grim officials enumerating the latest toll. By April 29, the virus had spread to at least nine countries, leading health officials to raise the alert level and warn that a pandemic is imminent; the most recent influenza pandemic, in 1968, killed around a million people.
Fear thrives on uncertainty, and the current swine-flu virus has left health officials pondering crucial, unanswered questions:...