X-Plain™ Tuberculosis Reference Summary Tuberculosis, or TB, is a bacterial infection that causes more deaths in the world than any other infectious disease. About 2 billion people are infected with tuberculosis worldwide. In the United States, about 15 million people are infected. When tuberculosis becomes active, it kills 60% of those who are not treated. This amounts to 3 million deaths worldwide every year. In the United States, about 20,000 tuberculosis infections become active every year. There is a treatment for tuberculosis. When treated, 90% of patients who have an active tuberculosis infection survive. This reference summary explains latent and active tuberculosis infections. The program discusses the diagnosis, treatment, and prevention of tuberculosis. Causes Tuberculosis is an infection caused by a bacterium called Mycobacterium tuberculosis. The bacterium is also called tubercle bacillus. Tuberculosis spreads from person to person through air as a person with active tuberculosis coughs, sneezes, or expels air.