Tuberculosis is an infection caused by a bacteria, mycobacterium tuberculosis.
If the bacteria enters the lung, it can multiply and can cause disease. It affects the lungs and, sometimes, other parts of the body. These secretions contain TB bacteria. If a person with tuberculosis is coughing and a shower of these droplets enters the air, people breathing that air may become infected. Health care workers may be exposed to the tuberculosis bacteria by taking care of patients with tuberculosis who have the bacteria in their sputum.