Journal of Tropical Diseases & Public Health

TB-HIV Coinfection

Tuberculosis (TB) and HIV (Human Immunodeficiency Virus) are two significant public health challenges that often co-occur, particularly in resource-limited settings. TB is a bacterial infection caused by Mycobacterium tuberculosis, while HIV is a virus that attacks the immune system, leading to acquired immunodeficiency syndrome (AIDS). The coexistence of these two infections significantly complicates treatment, increases morbidity and mortality, and poses challenges for public health efforts.

Epidemiology

• Global Burden: TB is one of the leading causes of death among people living with HIV. The World Health Organization (WHO) estimates that approximately one-quarter of the world's population is infected with TB, and among those living with HIV, TB is the most common opportunistic infection.
• Coinfection Rates: It is estimated that about 10% to 15% of people with HIV develop TB at some point in their lives, while HIV-positive individuals are 20 to 37 times more likely to develop active TB compared to HIV-negative individuals.

Pathophysiology

• Immune Suppression: HIV weakens the immune system, making individuals more susceptible to opportunistic infections like TB. The CD4+ T lymphocyte count is a crucial indicator of immune function in HIV-positive individuals; lower counts correlate with a higher risk of TB infection.
• TB Reactivation: In individuals with latent TB infection (LTBI), HIV can reactivate the dormant bacteria, leading to active TB disease.

Diagnosis

• Challenges: Diagnosing TB in HIV-positive individuals can be more challenging due to atypical presentations, lower sensitivity of diagnostic tests, and the possibility of extrapulmonary TB (TB occurring outside the lungs).
• Diagnostic Methods:
  • Tuberculin Skin Test (TST): Less reliable in HIV-positive individuals due to an impaired immune response.
  • Interferon Gamma Release Assays (IGRAs): Blood tests that are more effective for diagnosing latent TB in people with HIV.
  • Sputum Culture and Smear Microscopy: Essential for diagnosing active pulmonary TB.
  • Chest X-ray: Used to identify pulmonary TB, although it may present atypically in HIV-positive individuals.

Treatment

• Antiretroviral Therapy (ART): Starting ART is critical for managing HIV and reducing the risk of TB. It helps restore immune function and reduces mortality.
• TB Treatment:
  • Standard TB Regimen: Treatment typically involves a combination of antibiotics, commonly including:
    • Isoniazid
    • Rifampicin
    • Pyrazinamide
    • Ethambutol (for the initial phase)

• Timing of Therapy: The timing of starting ART in relation to TB treatment is crucial:
  • HIV-Positive Patients with TB: ART should ideally be initiated within the first 8 weeks of starting TB treatment, particularly if the CD4+ count is below 350 cells/mm³.

Complications

• Drug Interactions: Certain anti-TB medications can interact with antiretroviral drugs, necessitating careful management of treatment regimens.
• Immune Reconstitution Inflammatory Syndrome (IRIS): After starting ART, some individuals may experience a paradoxical worsening of TB symptoms due to an exaggerated immune response as their immune system begins to recover.

Prevention

• Screening: Routine screening for TB in people living with HIV is essential to detect latent TB infection and prevent progression to active disease.
• Preventive Therapy: Isoniazid preventive therapy (IPT) is recommended for HIV-positive individuals with latent TB infection to reduce the risk of developing active TB.
• Vaccination: The Bacillus Calmette-Guerin (BCG) vaccine is not routinely used in HIV-positive individuals due to its variable efficacy and the potential for disseminated BCG disease.

Public Health Implications

• Integrated Care: Effective management of TB and HIV coinfection requires an integrated approach that addresses both diseases simultaneously, including screening, diagnosis, and treatment.
• Global Efforts: Collaborative efforts among governments, NGOs, and healthcare providers are essential to reduce the burden of TB-HIV coinfection, particularly in high-burden countries.