More people die each year from tuberculosis than from any other infectious disease, the annual death toll being almost three million (over 95% of which are in developing countries) with eight million new cases being diagnosed every year. It is estimated that one-third of the world's population - nearly two billion people - is now infected, of which 5-10% will develop the disease. In 1993, the World Health Organization recognized tuberculosis as a 'global health emergency', the first time that a disease had ever been marked in this way. The emergence of drug-resistant forms of the disease combined with the paucity of new drugs makes the challenge of understanding and combating the disease especially urgent. This book explores the interplay between the Mycobacterium and its host by focusing on the research currently underway on the sequencing of the genome of Mycobacterium tuberculosis, and on the genetic and epidemiological studies of communities exposed to the disease (and on related animal models). From a synthesis of these data, new insights into the understanding of the pathogenesis, prevention and treatment of tuberculosis emerge.