A leading doctor offers answers on the one of the most urgent questions of our time: How do we prevent the next global pandemic?

The 2014 Ebola epidemic in Liberia terrified the world--and revealed how unprepared we are for the next outbreak of an infectious disease. Somewhere in nature, a killer virus is boiling up in the bloodstream of a bird, bat, monkey, or pig, preparing to jump to a human being. This not-yet-detected germ has the potential to wipe out millions of lives over a matter of weeks or months. That risk makes the threat posed by ISIS, a ground war, a massive...