Tuberculosis control activities focus on identification and treatment of sputum smear positive tuberculosis patients. As soon as these patients can be treated, they not only have an optimal chance for cure, they also no longer spread Mycobacterium tuberculosis (M.tb) in the community. Screening is a systematic search for tuberculosis disease, often performed by radiological or by sputum smear examinations. On the other hand, Screening for Infection with M.tb is with immunological tests. Persons infected with M.tb have an increased risk to develop active tuberculosis in the future. Screening for infection is recommended in tuberculosis contact tracing and in several risk groups for the progression to tuberculosis disease, specifically before the start of immunosuppressive therapy with tumor necrosis factor antagonists or in transplant recipients. Several immunological tests are available. If compared to the traditional in vivo Mantoux tuberculin skin test, in vitro blood tests called Interferon Gamma Release Assays (IGRA) are more specific because the cell wall antigens used for the tests are not present in the wall of Bacille Calmitte Guerin BCG and most atypical mycobacteria. Another advantage of IGRA is the mitogen positive control, which detects unreliable tests in immunodeficiency. Persons found to be infected with M.tb are treated with prophylactic isoniacid for 9 months.