Tuberculosis, or TB, is a preventable infectious disease caused by a bacterium called Mycobacterium tuberculosis. TB can attack any part of the body, but primarily attacks the lungs. TB disease was once a leading cause of death in the United States. Worldwide, TB still causes more deaths than any other infectious disease.During the 1940s, scientists discovered the first of many drugs used to treat TB. As a result, TB slowly began to disappear in the U.S. Unfortunately, TB infection has made a comeback in recent decades. After 1984, the number of TB cases reported in the U.S. began to increase. More than 25,000 cases were reported in 1993.