tuberculosis

tuberculosis
Name	Tuberculosis
Caption	Mycobacterium tuberculosis bacteria (stained red) in a sputum sample.
Field	Infectious disease, Pulmonology
Symptoms	Chronic cough, fever, night sweats, weight loss
Complications	Miliary tuberculosis, Pott disease, Meningitis
Onset	Weeks to years after exposure
Duration	Requires months of treatment
Causes	Mycobacterium tuberculosis
Risks	HIV/AIDS, Diabetes mellitus, Malnutrition, Smoking
Diagnosis	Chest X-ray, Sputum culture, Tuberculin skin test, Interferon-gamma release assay
Prevention	BCG vaccine, screening high-risk groups
Treatment	Antibiotics (e.g., Isoniazid, Rifampicin)
Medication	First-line anti-tuberculosis medications
Prognosis	Good with treatment
Frequency	~10 million new cases annually (2022)
Deaths	~1.3 million annually (2022)

tuberculosis. It is a communicable disease caused by the bacterium Mycobacterium tuberculosis, which most commonly affects the lungs. The infection is spread through the air when people with active pulmonary disease cough, sneeze, or speak. While a significant global health issue, it is preventable and curable with appropriate public health measures and medical treatment.

Overview

The disease has been known since antiquity, with evidence found in Egyptian mummies and described by Hippocrates. The causative agent was identified in 1882 by Robert Koch, a discovery for which he later received the Nobel Prize in Physiology or Medicine. The World Health Organization classifies it as a major global health threat alongside HIV/AIDS and Malaria. The Bacillus Calmette–Guérin vaccine, developed in the early 20th century, remains the only licensed vaccine, though its efficacy is variable.

Causes and transmission

The disease is caused by bacteria in the Mycobacterium tuberculosis complex. Transmission occurs via inhalation of airborne Droplet nuclei expelled by individuals with active, untreated pulmonary infection. Key risk factors that increase susceptibility include co-infection with HIV, which severely compromises the Immune system, as well as conditions like Diabetes mellitus and states of Malnutrition. Other significant risks are prolonged close contact in crowded settings such as Prisons or Homeless shelters, and behaviors like Smoking.

Signs and symptoms

Active pulmonary disease typically presents with a persistent Chronic cough lasting more than three weeks, often accompanied by Hemoptysis. Systemic symptoms include Fever, Night sweats, and significant Weight loss, collectively known as consumption. Extrapulmonary manifestations can affect almost any organ system; common sites include the Pleural cavity, Lymph nodes, Genitourinary system, Bones and joints (as in Pott disease), and the Central nervous system, leading to Meningitis.

Diagnosis

Diagnosis involves a combination of methods. A Chest X-ray often shows abnormalities in the upper lobes. Microbiological confirmation is achieved by identifying acid-fast bacilli in Sputum smears via Ziehl–Neelsen stain and culturing the bacteria on Lowenstein–Jensen medium. The Tuberculin skin test and blood-based Interferon-gamma release assays, such as the QuantiFERON, detect latent infection. Molecular tests like the Xpert MTB/RIF assay, endorsed by the World Health Organization, allow for rapid detection and identification of Rifampicin resistance.

Prevention

Prevention strategies center on vaccination and infection control. The Bacillus Calmette–Guérin vaccine is widely used in countries with high burden, though it offers inconsistent protection against pulmonary disease in adults. Preventing transmission in healthcare settings involves the use of Ultraviolet germicidal irradiation and N95 respirators. Public health programs focus on active Case finding and treating latent infection with regimens like Isoniazid preventive therapy, particularly in contacts of active cases and people living with HIV.

Treatment and management

Standard treatment for drug-susceptible disease requires a multi-drug regimen administered under Directly observed therapy to ensure adherence. The first-line regimen typically includes Isoniazid, Rifampicin, Ethambutol, and Pyrazinamide for two months, followed by Isoniazid and Rifampicin for four months. Management of drug-resistant forms, such as Multidrug-resistant tuberculosis and Extensively drug-resistant tuberculosis, involves longer, more complex regimens with second-line drugs like Bedaquiline and Delamanid, often requiring supervision at specialized centers like the National Jewish Health hospital.

Epidemiology

It remains a leading cause of death from a single infectious agent globally. In 2022, the World Health Organization estimated approximately 10 million new cases and 1.3 million deaths. The burden is highest in the South-East Asia and African regions, with countries like India, Indonesia, and Nigeria reporting the most cases. Major initiatives to combat the disease include the WHO End TB Strategy and the support of organizations like the Global Fund to Fight AIDS, Tuberculosis and Malaria and the Stop TB Partnership.

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