Natural viruses and bacteria can be deadly enough; the 1918 Spanish Flu killed 50 million people in four months. But risky new research, carried out in an unknown number of labs around the world, are creating even more dangerous humanmade pathogens. (Original score by Point Lobo.) 

Interviewees: Beth Willis, former chair, Containment Laboratory Community Advisory Committee; Dr Lynn Klotz, senior fellow at the Center for Arms Control and Non-Proliferation.