Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis that mainly affects the lungs. It can spread through droplets in the air from coughing or sneezing. Symptoms include coughing, chest pain, and fatigue. Diagnosis involves sputum tests, chest x-rays, and tuberculin skin tests. Treatment involves a combination of antibiotics taken for 6-9 months. Preventive measures include BCG vaccination, isolation, and proper ventilation. Drug-resistant TB strains like MDR-TB and XDR-TB require longer and more toxic treatment regimens. HIV co-infection increases the risk of active TB disease.