Tuberculosis (TB) is a serious infectious disease caused by the bacterium Mycobacterium tuberculosis, most commonly affecting the lungs but potentially spreading to other parts of the body such as the kidneys, spine, or brain. It spreads through the air when people with active TB disease cough, sneeze, speak, or spit, releasing tiny droplets containing the bacteria that others can inhale. Many infected individuals develop latent TB infection, where the bacteria remain dormant without causing symptoms or being contagious, but in some cases—especially if the immune system weakens—the infection progresses to active TB disease, characterized by persistent cough (often lasting weeks or producing blood-tinged sputum), chest pain, fatigue, weight loss, fever, and night sweats. TB is both preventable and curable with a course of antibiotics (typically lasting 4–6 months or longer for drug-resistant strains), though multidrug-resistant forms pose ongoing challenges globally; without proper treatment, it can be fatal and remains one of the world’s leading causes of death from a single infectious agent.