Tuberculosis (TB) is a communicable infectious disease caused mainly by Mycobacterium tuberculosis. It mostly affects the lungs (pulmonary TB) but can also spread to other parts of the body (extrapulmonary TB). TB spreads through tiny droplets released when a person with active TB coughs, sneezes or speaks.
Healthy individuals often contain the infection without symptoms — this is called latent TB. When immunity weakens (HIV, old age, malnutrition), the bacteria become active and cause tissue destruction, leading to active TB, which can be fatal if untreated.
Epidemiology
- TB is one of the world’s most common infectious diseases.
- India has the highest TB burden globally.
- WHO reports that 2–3 million Indians suffer TB every year out of a global 8.7 million cases.
- It is one of India’s biggest public health challenges.
Etiology
TB is caused by Mycobacterium tuberculosis. Infection occurs when a person inhales infected droplets released by someone with active TB during coughing, laughing, speaking or sneezing.
Risk Factors
- HIV infection (strongest risk factor)
- Frequent close contact with TB patients
- Malnutrition
- Poverty and poor living conditions
- Old age
- Alcoholism and smoking
- Diabetes
- Chronic lung diseases
- Immunosuppressive therapy (steroids, TNF-α inhibitors)
Pathophysiology
When droplet nuclei are inhaled, bacteria reach the alveoli, where they are taken up by macrophages. TB organisms survive inside these cells and multiply.
Body responds by forming a granuloma — a structured collection of macrophages and lymphocytes that walls off the bacteria. People with granulomas but no symptoms have latent TB and are not contagious.
About 10% of people with latent TB may develop active disease in their lifetime, especially within the first 2 years of infection. HIV patients have up to 10% risk per year.
Clinical Manifestations
Symptoms of Active Pulmonary TB
- Persistent cough for more than 2 weeks
- Green, yellow or blood-stained sputum
- Low-grade fever
- Night sweats
- Weight loss and anorexia
- Fatigue and general weakness
- Chest pain and shortness of breath
- Hemoptysis (coughing up blood)
Extrapulmonary TB Symptoms
Depends on site:
- Lymph nodes: swelling in neck or armpit
- Bones/joints: pain in spine, hip or knee
- Genitourinary TB: painful urination, flank pain, blood in urine
- Meningeal TB: headache, stiff neck, confusion
Diagnosis
1) Medical History & Physical Examination
Symptoms such as chronic cough, fever, night sweats and weight loss are evaluated.
2) Laboratory Tests
- Sputum smear & culture: confirms active TB but culture may take weeks.
- Sputum cytology: checks for abnormal cells.
- Tuberculin Skin Test (Mantoux): small injection tested after 48–72 hrs.
- TB blood tests: (IGRA) measures immune response to TB.
3) Imaging
- Chest X-ray: shows lung lesions or cavities.
- CT/MRI: used for extrapulmonary TB.
4) Diagnosis of Extrapulmonary TB
- Biopsy of affected tissue
- Urine culture (renal TB)
- Lumbar puncture (TB meningitis)
Drug Resistance Tests
Drug susceptibility testing is vital, especially when treatment fails or TB is suspected to be drug resistant.
Treatment
First-Line Drugs
- Isoniazid (INH)
- Rifampicin
- Pyrazinamide
- Ethambutol
- Streptomycin
Standard treatment usually lasts 6 months. More than one drug must always be used to prevent resistance.
Second-Line Drugs
- Para-aminosalicylic acid
- Ethionamide
- Cycloserine
- Kanamycin
- Rifabutin
Treatment of MDR-TB
Multidrug-resistant TB (MDR-TB) requires stronger medicines for 18–24 months. Newer drugs include bedaquiline, delamanid, linezolid and sutezolid.
DOTS (Directly Observed Treatment, Short-course)
DOTS is WHO’s recommended TB control strategy. It includes:
- Strong government commitment
- Diagnosis by sputum smear microscopy
- Standardized treatment directly observed by a health worker
- Uninterrupted supply of TB medicines
- Standardized recording and reporting system
Prevention
1) Education & Screening
- Identify people exposed to TB patients
- Encourage early check-ups and testing
- Cover mouth while coughing to prevent droplet spread
2) Early Diagnosis and Treatment
Treating active TB early reduces severe complications and prevents transmission.
3) Healthy Lifestyle
- Good nutrition
- Avoid smoking and alcohol
- Get adequate sleep and exercise
4) BCG Vaccination
Newborns in high-risk areas receive BCG vaccine to protect against severe childhood TB.
How TB Spreads
TB is spread by:
- Coughing, sneezing, singing, laughing by active TB patients
TB is NOT spread by:
- Casual contact
- Sharing food, utensils, cigarettes or drinks
- Shaking hands
- Using public phones
Detailed Notes:
For PDF style full-color notes, open the complete study material below: