Every second, someone becomes infected with tuberculosis (TB) someplace on Earth. Mycobacterium tuberculosis generally affects the lungs, but can attack any organ. TB occurs along a continuum, and infected individuals may have latent or active TB. In the United States, public health efforts between 1953 and the early 1980s successfully reduced the number of cases. The number began to grow in the 1980s, and several causes were implicated. In the last few years, the number of active TB cases has declined significantly, but drug-resistant TB has become a growing concern. The elderly are at high risk for TB, especially if they are long-term care residents.