Tuberculosis (TB) is not a hereditary disease; it is an infectious disease caused by the bacterium Mycobacterium tuberculosis. The primary sources of TB infection are patients and animals, particularly cattle, that excrete the bacteria. Open pulmonary TB patients who excrete bacteria are the main source of infection. After undergoing proper chemotherapy, as the amount of bacteria in the sputum decreases, the infectiousness of the disease diminishes. TB is primarily transmitted through the air. When TB patients cough or sneeze, the tuberculosis bacteria are suspended in droplet nuclei, which can be inhaled by healthy individuals, leading to infection. Inhaling dried sputum containing tuberculosis bacteria along with dust can also cause infection. Other routes of transmission, such as drinking contaminated milk leading to gastrointestinal infection, are extremely rare.