Unit
- Epidemiological scale: Tuberculosis is among the top 10 causes of death worldwide, with approximately 10 million new cases annually. The highest burden occurs in Southeast Asia, Africa, and the Western Pacific regions. Understanding these figures helps administrators allocate resources effectively.
- Transmission dynamics: Mycobacterium tuberculosis spreads via airborne droplets when an infected person coughs or sneezes. Close contact for prolonged periods increases risk. Poor ventilation and overcrowded settings amplify transmission, making infection control a priority in congregate settings.
- Latent vs. active TB: About one-quarter of the global population has latent TB infection, meaning they carry the bacteria without symptoms and are not contagious. Active TB develops when the immune system fails to contain the infection, causing cough, fever, night sweats, and weight loss.
- Risk factors: HIV coinfection, malnutrition, diabetes, smoking, and immunosuppressive therapies significantly increase the risk of progressing from latent to active TB. Administrators must consider these factors when designing screening programs for high-risk populations.
- Socioeconomic impact: TB disproportionately affects impoverished communities with limited access to healthcare. The disease can lead to lost productivity, catastrophic health expenditures, and stigma. Program managers should integrate social support into control strategies.
- Drug-resistant TB: Multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) pose a growing threat. Resistance arises from improper treatment or incomplete adherence. Managing drug-resistant cases requires specialized regimens and prolonged follow-up.
- Historical context: TB was once a leading cause of death in industrialized nations. The advent of antibiotics in the mid-20th century reduced incidence, but resurgence in the 1980s due to HIV and neglect led to renewed global efforts such as the WHO End TB Strategy.
- Global targets: The World Health Organization aims for a 90% reduction in TB incidence and a 95% reduction in deaths by 2035 compared to 2015 levels. Progress requires strengthened health systems, universal health coverage, and multisectoral collaboration.
- Diagnostic methods: Smear microscopy remains a rapid, low-cost tool for detecting acid-fast bacilli in sputum. Culture is the gold standard but takes weeks. Molecular tests like GeneXpert simultaneously detect TB and rifampicin resistance within two hours, greatly improving case detection and guiding treatment decisions in resource-limited settings, enabling prompt initiation of appropriate therapy.
- Treatment regimens: Standard first-line therapy for drug-sensitive pulmonary TB consists of a 2-month intensive phase with isoniazid, rifampicin, pyrazinamide, and ethambutol, followed by a 4-month continuation phase with isoniazid and rifampicin. Adherence is critical; directly observed therapy (DOT) significantly improves completion rates and reduces relapse. Poor adherence can lead to acquired drug resistance.
- Prevention strategies: Bacillus Calmette-Guerin (BCG) vaccination is widely used in high-burden countries to protect infants against severe disseminated TB and tuberculous meningitis. Infection control in healthcare settings includes airborne precautions, adequate ventilation, and use of N95 respirators. Latent TB infection treatment with isoniazid or rifampicin reduces the risk of progression to active disease by up to 90%.
Terminology
- Latent TB infection (LTBI)
- A state where a person is infected with M. tuberculosis but has no active disease and cannot transmit the bacteria.
- Active TB disease
- Symptomatic infection that can spread to others, typically diagnosed by positive culture or nucleic acid amplification test.
- MDR-TB
- Tuberculosis resistant to at least isoniazid and rifampicin, the two most effective first-line drugs.
Quick Revision
- Tuberculosis is a major global killer, with 10 million new cases each year.
- Transmission occurs via airborne droplets; risk increases in crowded, poorly ventilated spaces.
- Latent TB infection is asymptomatic and noncontagious; active TB requires treatment.
- Risk factors include HIV, malnutrition, diabetes, and immunosuppression.
- Drug-resistant forms threaten progress and demand specialized management.