The struggle against deadly microbes is endless. Diseases that have plagued human beings since ancient times still exist, new maladies make their way into the headlines, we are faced with vaccine shortages, and the threat of germ warfare has reemerged as a worldwide threat. In this riveting account, medical historian Howard Markel takes an eye-opening look at the fragility of the American public health system. He tells the distinctive stories of six epidemics-tuberculosis, bubonic plague, trachoma, typhus, cholera, and AIDS-to show how our chief defense against diseases from outside the United States has been to attempt to deny entry to carriers. He explains why this approach