Tuberculosis (TB) remains one of the most serious infectious diseases globally, caused by the bacterium Mycobacterium tuberculosis. It primarily affects the lungs but can also spread to other organs, including the brain, spine, and kidneys. Despite being preventable and curable, TB continues to pose a significant public health challenge, especially in developing nations.
What Is Tuberculosis?
Tuberculosis is an airborne bacterial infection that spreads through droplets released when a person with active pulmonary TB coughs, sneezes, or speaks. There are two main forms:
- Latent TB Infection (LTBI): The bacteria remain in the body in an inactive state and cause no symptoms.
- Active TB Disease: The bacteria multiply and cause noticeable symptoms, and the patient is contagious.
Without proper treatment, active TB can be fatal.
Causes and Transmission of TB
1. Bacterial Cause
The pathogen responsible is Mycobacterium tuberculosis, a slow-growing, acid-fast bacillus. Its waxy cell wall allows it to survive in hostile environments and resist many common antibiotics.
2. Mode of Transmission
TB is transmitted via the airborne route. Prolonged close contact with an infected person increases the risk. It cannot be spread through:
- Handshakes
- Shared food or drinks
- Toilets or bedding
3. Risk Factors
- HIV infection
- Diabetes mellitus
- Substance abuse
- Malnutrition
- Use of immunosuppressive drugs
- Living in crowded conditions
- Exposure in healthcare settings
Symptoms of Tuberculosis
Pulmonary TB Symptoms
- Persistent cough (lasting more than 3 weeks)
- Coughing up blood or sputum
- Chest pain
- Fever and night sweats
- Weight loss and loss of appetite
- Fatigue and weakness
Extrapulmonary TB Symptoms
Occurs when TB affects organs other than the lungs:
- TB Meningitis: Headache, confusion, stiff neck
- TB Lymphadenitis: Swollen, painful lymph nodes
- Skeletal TB: Back pain (spinal TB), joint swelling
- Genitourinary TB: Pelvic pain, blood in urine
- Miliary TB: Disseminated form presenting with multiple small lesions in multiple organs
Diagnosis of Tuberculosis
1. Medical History and Physical Exam
A thorough evaluation includes risk factor assessment and checking for physical signs like lung rales, swollen lymph nodes, and weight loss.
2. Tuberculin Skin Test (TST)
Also known as the Mantoux test, this involves injecting a small amount of purified protein derivative (PPD) into the skin. A raised bump indicates exposure, though not necessarily active disease.
3. Interferon-Gamma Release Assays (IGRAs)
Blood tests such as QuantiFERON-TB Gold measure the immune response to TB bacteria and are preferred in BCG-vaccinated individuals.
4. Sputum Tests
- Acid-fast bacilli (AFB) smear microscopy
- Sputum culture (gold standard for diagnosis)
- Nucleic Acid Amplification Tests (NAATs) like GeneXpert MTB/RIF detect TB DNA and resistance to rifampicin.
5. Imaging
- Chest X-rays or CT scans reveal cavities, infiltrates, or nodular lesions typically found in the upper lobes of the lungs.
Treatment Options for Tuberculosis
1. Standard Drug Therapy for Active TB
The first-line treatment includes a 6-month regimen:
- Intensive Phase (first 2 months): Isoniazid, Rifampicin, Pyrazinamide, Ethambutol
- Continuation Phase (next 4 months): Isoniazid and Rifampicin
2. Treatment for Latent TB
To prevent reactivation, LTBI is treated with:
- Isoniazid for 6–9 months
- Rifampicin for 4 months
- Combination therapy (Isoniazid + Rifapentine weekly for 3 months)
3. Drug-Resistant TB (DR-TB)
- Multidrug-resistant TB (MDR-TB): Resistant to isoniazid and rifampicin
- Extensively drug-resistant TB (XDR-TB): Resistant to first-line and several second-line drugs
Treatment involves longer, more toxic regimens including fluoroquinolones, bedaquiline, linezolid, and cycloserine.
4. Directly Observed Treatment, Short-course (DOTS)
A globally recommended strategy ensuring patient compliance by having a health worker monitor each dose taken.
TB Prevention Strategies
1. BCG Vaccination
The Bacillus Calmette-Guérin (BCG) vaccine is administered at birth in high-burden countries. It offers partial protection, especially against severe pediatric forms like miliary TB and TB meningitis.
2. Infection Control Measures
- Ensuring ventilation in healthcare settings
- Using respiratory protective equipment
- Isolating active TB cases
- Implementing airborne precautions
3. Contact Tracing and Screening
Close contacts of TB patients should be screened using IGRA or TST, followed by chest X-ray if needed.
4. Nutrition and Immune Support
Proper nutrition, stress management, and addressing comorbidities like HIV or diabetes improve overall immunity and reduce TB risk.
Complications of Untreated TB
- Massive hemoptysis (coughing up blood)
- Respiratory failure
- Bronchiectasis
- Chronic lung damage
- Spinal deformities (in skeletal TB)
- Meningeal TB can lead to coma or death
- Increased mortality in HIV-positive individuals
Tuberculosis and HIV Co-Infection
TB is the leading cause of death among people with HIV/AIDS. Co-infection complicates diagnosis and treatment.
Special Considerations
- Start antiretroviral therapy (ART) within 2 weeks of TB treatment if CD4 count is below 50 cells/μL.
- Drug interactions between rifampicin and ART drugs must be carefully managed.
Global Burden of Tuberculosis
- According to the WHO Global TB Report, over 10 million people fall ill with TB annually.
- TB kills over 1.3 million people every year, making it the second leading infectious killer after COVID-19.
- High-burden countries include India, China, Indonesia, Nigeria, and the Philippines.
Living With and Managing Tuberculosis
1. Medication Adherence
Skipping doses or stopping treatment early can lead to drug resistance, treatment failure, and relapse.
2. Psychological Support
TB carries a social stigma in many cultures. Counseling and community support play a vital role in treatment adherence and mental well-being.
3. Regular Follow-Up
Frequent visits help monitor treatment response, detect side effects early, and prevent relapse.
4. Public Awareness and Education
Educating communities about TB symptoms, transmission, and the importance of early diagnosis can drastically reduce transmission rates.
Conclusion: Combating Tuberculosis Requires Unified Effort
Tuberculosis is not merely a medical condition but a social disease that reflects inequality, poverty, and poor health infrastructure. A multidisciplinary approach involving early detection, appropriate therapy, vaccination, and public health education is essential to control and ultimately eliminate TB.
