Tuberculosis continues to be the leading cause of death in the world from a single infectious organism. Each year there are an estimated 8 rnillion new cases of the disease worldwide. Approximately one-third of the global population is believed to have latent infection and is therefore at risk of developing the disease. In parts of the developed world, the steady decline in the incidence of TB over the past century has recently ceased or even reversed. The resurgence has been attributed to a combination of deterioration of specific TB control programs, the HIV epidemic, immigration from countries where infection is highly prevalent, emergence of multidrug resistant strains, rising poverty, and homelessness and overcrowding among urban populations. In 1993 the World Health Organization declared that tuberculosis was a global emergency.