Imagine a world where affordable, quality health care is available to every person, and where infectious disease and infant and maternal mortality are as rare in the poorest parts as they are in wealthier countries. The world has already come a long way toward meeting this goal. But to finish the job, we need to change our thinking. To be sure, the incidence of child mortality and cases of deadly infectious diseases have dropped dramatically around the world. For example, polio, which once paralyzed a thousand children every day, has been eliminated from all but three countries, with just 33 cases last year.