HCWs refers to all paid and unpaid persons working in healthcare settings who have the potential for exposure to M. tuberculosis . TB is spread primarily by airborne droplets coughed up from the lungs of persons with active disease. Once inhaled, the organisms establish infection in the lungs and then disseminate throughout the body before the immune response brings the primary in fection under control.
Most infected persons have no symptoms of disease.
Following infection a small percentage of individuals will develop symptoms. About ten percent of persons who become infected will develop an active case of TB during their lifetime s. For decades the prevalance of tuberculosis in the United States was declining. Since the mid 1980's, however, the number of tuberculosis cases increased. This increase appears to be fueled by the development of the epidemic of HIV infection in this count ry.