TB is an abbreviation for tuberculosis, an infectious disease caused primarily by the bacterium Mycobacterium tuberculosis, characterised by granulomatous lesions most commonly affecting the lungs but capable of involving multiple organs.
Explanation
Tuberculosis is transmitted via respiratory droplets and is one of the leading causes of infectious mortality worldwide. After inhalation, M. tuberculosis bacilli are engulfed by alveolar macrophages but persist and replicate within phagosomes, provoking a cell‑mediated immune response that forms granulomas. In most immunocompetent individuals the infection becomes latent and noncontagious, but about 10 percent develop active disease, particularly those with malnutrition, HIV infection or other immunocompromising conditions. Clinical manifestations of pulmonary TB include chronic cough, hemoptysis, weight loss, night sweats and fever. Extrapulmonary TB can affect lymph nodes, bones, the meninges and other organs. Diagnosis involves sputum microscopy, culture, nucleic acid amplification tests and radiographic imaging. Treatment requires prolonged multidrug regimens, typically six months of isoniazid, rifampicin, pyrazinamide and ethambutol for drug‑susceptible disease. Drug‑resistant TB strains, such as multidrug‑resistant (MDR‑TB) and extensively drug‑resistant TB, pose serious public health challenges. Preventive measures include screening and treatment of latent infection, BCG vaccination in high‑incidence countries and infection control in healthcare settings.
Clinical Presentation and Control
Symptoms of active pulmonary TB range from persistent productive cough and chest pain to systemic signs such as fatigue, weight loss, fever and night sweats. In miliary TB the bacteria disseminate throughout the body, leading to liver, spleen and bone marrow involvement; TB meningitis causes severe neurological deficits. Diagnosis can be supported by tuberculin skin testing or interferon‑gamma release assays, but these tests do not distinguish latent from active disease. Effective control requires adherence to directly observed therapy, contact tracing, vaccination programmes and public health measures to reduce transmission, particularly in settings with high HIV co‑infection rates. Development of new vaccines and shorter treatment regimens is ongoing to curb the global TB burden.
TB remains a major global health problem. Early detection, effective treatment and preventive strategies are crucial to reduce morbidity and mortality.
Related Terms: Mycobacterium tuberculosis, Tubercle, Latent infection, BCG vaccine, MDR‑TB