Tuberculosis (TB) is an infectious disease primarily of the respiratory system caused by bacteria. Most human cases are attributable to species in the mycobacteria group, especially Mycobacterium tuberculosis. Historically known as "consumption," TB can present as active pulmonary disease or as a latent infection that may reactivate later in life. It remains an important global public‑health problem because of its persistence, potential severity, and interaction with other conditions.
Characteristics and transmission
TB is transmitted most often when someone with active pulmonary disease expels infectious droplets by coughing, speaking or sneezing; those droplets are inhaled by others. After exposure, the organism may be contained by the immune system, producing a latent infection without symptoms, or may progress to active disease with symptoms such as a persistent cough, fever, night sweats, weight loss and sometimes coughing up blood. Although the lungs are most commonly affected, TB can involve many organs (extrapulmonary TB), including lymph nodes, bones, kidneys and the lining of the brain.
Diagnosis and clinical features
Diagnosis combines clinical assessment, imaging and laboratory tests. Common tools include chest radiography, microscopic examination and culture of sputum, nucleic acid amplification tests, skin testing and interferon‑gamma release assays to detect immunological evidence of infection. Distinguishing latent infection from active disease is central to management and public‑health response.
Treatment and drug resistance
Treating drug‑sensitive TB typically requires a multi‑drug antibiotic regimen given for several months to prevent relapse and resistance. Standard courses commonly use isoniazid, rifampicin, pyrazinamide and ethambutol in initial phases. Drug‑resistant forms — notably multidrug‑resistant TB (MDR‑TB) and extensively drug‑resistant TB (XDR‑TB) — arise when strains become resistant to key antibiotics, making therapy longer, more complex and less certain in outcome.
Prevention, vaccination and public health
Prevention combines case finding, appropriate treatment of active cases to stop transmission, contact tracing and social measures that reduce overcrowding and improve nutrition and ventilation. A vaccine, bacille Calmette‑Guérin (BCG), offers useful protection against severe childhood forms of TB but provides variable protection against adult pulmonary disease. Public‑health approaches also include directly observed therapy (DOT) programs, screening of high‑risk groups, and integration with HIV services because HIV infection increases the risk of progression from latent to active TB.
History, impact and notable facts
Evidence of TB appears in ancient texts and skeletal remains; the causal bacterium was identified by Robert Koch in 1882, a milestone that paved the way for modern diagnostics and treatment. Despite effective drugs and vaccines, TB persists due to social inequality, health system gaps and the emergence of resistant strains. Ongoing research focuses on faster diagnostics, shorter treatment regimens, new drugs and improved vaccines.
For more detailed scientific and public‑health information, consult sources on the causative bacteria and authoritative health guidance at reputable institutions and research bodies. Additional background and resources are available through general summaries and technical pages: mycobacterial biology, M. tuberculosis summaries and materials on respiratory disease control here.
