A nuclear holocaust was our worst fear for decades during the Cold War, but prophets of doom have now raised the specter of a different kind of holocaust, a swift and lethal plague that no vaccine or drug can stop. Is such a nightmare possible? While no scientist believes that entire cities could be wiped out, a menacing threat to human life could infect and wipe out millions around the world. Deadly viruses, bacteria and parasites are returning to haunt us. Every corner of the world is now within reach. Exotic microbes can travel from the heart of Africa to New York City in a single day. In a world of changing climate and surging populations, microbes are finding new openings to infect us and spread, and, we discover, there are many more diseases out there than we have names for.