Introduction

Tuberculosis (TB) is a contagious infectious disease primarily caused by the bacterium Mycobacterium tuberculosis. It remains one of the top 10 causes of death worldwide, with millions of new cases and deaths each year. TB primarily affects the lungs (pulmonary TB) but can impact other organs (extrapulmonary TB). Despite being curable and preventable, TB continues to pose significant public health challenges due to drug resistance, social determinants, and health system limitations.

Main Concepts

1. Etiology and Transmission

  • Causative Agent: Mycobacterium tuberculosis, a slow-growing, aerobic, acid-fast bacillus.
  • Transmission: Airborne; spread via droplets from coughs, sneezes, or speaking by individuals with active pulmonary TB.
  • Reservoir: Humans are the primary reservoir; animal TB (e.g., M. bovis) can also infect humans, typically through unpasteurized dairy products.

2. Pathogenesis

  • Infection Process: Inhaled bacilli reach the alveoli, where they are phagocytosed by macrophages. The immune system may contain the infection, leading to latent TB, or fail, resulting in active disease.
  • Latent TB Infection (LTBI): The bacteria remain dormant; individuals are asymptomatic and non-infectious but can develop active TB if immunity wanes.
  • Active TB Disease: Characterized by symptoms and the ability to transmit the disease.

3. Clinical Manifestations

  • Pulmonary TB: Chronic cough, hemoptysis, chest pain, night sweats, fever, weight loss, fatigue.
  • Extrapulmonary TB: May involve lymph nodes, pleura, bones, joints, genitourinary tract, meninges, or disseminate as miliary TB.
  • Risk Groups: People with HIV/AIDS, diabetes, malnutrition, smokers, and those in close contact with TB patients.

4. Diagnosis

  • Screening Tests: Tuberculin skin test (TST), interferon-gamma release assays (IGRAs).
  • Definitive Diagnosis: Sputum smear microscopy, culture, nucleic acid amplification tests (NAATs), chest radiography.
  • Drug Resistance Testing: Molecular assays (e.g., Xpert MTB/RIF) to detect resistance to rifampicin and other drugs.

5. Treatment

  • First-Line Drugs: Isoniazid, rifampicin, ethambutol, pyrazinamide (usually for 6 months).
  • Drug-Resistant TB: Multidrug-resistant TB (MDR-TB) requires longer, more complex regimens with second-line drugs (e.g., fluoroquinolones, bedaquiline).
  • Directly Observed Therapy (DOT): Ensures adherence to treatment to prevent resistance.

6. Prevention

  • BCG Vaccine: Bacillus Calmette-Guérin (BCG) provides variable protection, especially in children.
  • Infection Control: Early detection, isolation of infectious cases, use of masks, and ventilation in healthcare settings.
  • Contact Tracing: Identifying and treating latent TB in high-risk contacts.

Controversies

1. Vaccine Efficacy

  • The BCG vaccine’s effectiveness varies geographically and does not reliably prevent adult pulmonary TB.
  • Ongoing research into new vaccines (e.g., M72/AS01E) has shown promise, but widespread adoption and long-term efficacy remain under debate.

2. Drug Resistance

  • The rise of MDR-TB and extensively drug-resistant TB (XDR-TB) challenges current treatment protocols.
  • Access to new drugs (e.g., bedaquiline, delamanid) is limited in low-resource settings, raising ethical concerns about equity.

3. Social Determinants

  • TB disproportionately affects marginalized populations, including those living in poverty, crowded conditions, or with limited access to healthcare.
  • Stigma associated with TB can delay diagnosis and treatment, perpetuating transmission.

Relation to Current Events

Impact of COVID-19 Pandemic

  • The COVID-19 pandemic has disrupted TB services globally, leading to reduced case detection, delayed treatment, and increased mortality.
  • According to the World Health Organization’s Global Tuberculosis Report 2023, an estimated 10.6 million people fell ill with TB in 2022, with TB deaths rising for the second consecutive year, reversing years of progress (WHO, 2023).
  • The overlap of symptoms between COVID-19 and TB (e.g., cough, fever) complicates diagnosis and may lead to misdiagnosis or missed cases.

Plastic Pollution and TB

  • Recent studies have detected microplastics in the deepest ocean trenches, highlighting environmental pollution’s reach. While not directly linked, environmental degradation and poor living conditions can exacerbate TB risk factors, such as malnutrition and respiratory health, especially in vulnerable communities.

Tuberculosis and Health

  • Public Health Impact: TB remains a leading cause of death from infectious disease, particularly in low- and middle-income countries.
  • Co-morbidities: TB is a major cause of morbidity and mortality among people living with HIV/AIDS. Diabetes and malnutrition also increase susceptibility.
  • Global Health Goals: TB control is integral to the Sustainable Development Goals (SDGs), aiming to end the TB epidemic by 2030.
  • Antimicrobial Resistance: TB is a primary driver of antimicrobial resistance (AMR), threatening the effectiveness of current antibiotics.

Recent Research

A 2022 study published in The Lancet Infectious Diseases evaluated the efficacy of a new TB vaccine candidate, M72/AS01E, in preventing active pulmonary TB among adults with latent infection. The study found a 49.7% efficacy rate over three years, representing significant progress in TB vaccine development, though further research is needed to confirm long-term protection and effectiveness across diverse populations (Tait et al., 2022).

Conclusion

Tuberculosis remains a complex global health challenge influenced by biological, social, and environmental factors. Advances in diagnostics, treatment, and vaccine development offer hope, but persistent controversies and emerging threats like drug resistance and health system disruptions underscore the need for sustained investment and innovation. Addressing TB requires a multidisciplinary approach, integrating medical, social, and environmental strategies to reduce the disease burden and achieve global health targets.