Bubonic plague, smallpox, polio, HIV—the timeline of history is punctuated with diseases that have shaped the social atmospheres of the eras, defined the scope of science and medicine, and stolen many great minds before their time. But there is one disease that seems to have stalked humanity far longer than any other: tuberculosis. Fossil evidence indicates that TB has haunted humans for more than half a million years. No one is exempt. It affects rich and poor, young and old, risk takers and the abstinent. Simply by coughing, spitting or even talking, an infected individual can spread the bacterium that causes the disease.