Overview
Chronic bacterial infection primarily affecting the lungs, caused by Mycobacterium tuberculosis. The world's deadliest infectious disease with 10.8 million new cases and 1.25 million deaths annually.
Symptoms
Symptoms | Frequency | Severity | Onset |
|---|---|---|---|
| Cough | 95% | Moderate | Early |
| Fever | 60% | Mild | Early |
| Loss of appetite | 55% | Mild | Early |
| Night sweats | 70% | Mild | Early |
| Weight loss | 65% | Moderate | Early |
| Chills | 30% | Mild | Early |
| Malaise | 60% | Mild | Early |
| Hemoptysis | 20% | Severe | Peak |
| Productive cough | 80% | Moderate | Peak |
| Chest tightness | 40% | Moderate | Peak |
| Shortness of breath | 35% | Moderate | Peak |
| Wheezing | 15% | Mild | Peak |
| Back pain | 10% | Moderate | Late |
| Confusion | 3% | Severe | Late |
| Headache | 8% | Moderate | Late |
| Joint swelling | 5% | Mild | Late |
| Neck stiffness | 5% | Severe | Late |
| Dark urine | 3% | Mild | Late |
| Fatigue | 75% | Mild | Any phase |
| Swollen lymph nodes | 25% | Mild | Any phase |
| Abdominal pain | 8% | Mild | Any phase |
Transmission
Overview
Infectious disease primarily affecting the lungs, caused by Mycobacterium tuberculosis.
Overview
Tuberculosis (TB) is caused by Mycobacterium tuberculosis, a slow-growing acid-fast bacillus transmitted via airborne droplet nuclei (1–5 μm particles that remain suspended in air for hours). TB primarily affects the lungs (pulmonary TB, ~85%) but can involve any organ (extrapulmonary TB: lymph nodes, bones, CNS, kidneys, etc.). After exposure, 5–10% of immunocompetent individuals develop active TB (usually within 2 years); the remainder harbor latent TB infection (LTBI) — asymptomatic, non-infectious, but with lifetime 5–15% risk of reactivation. HIV co-infection dramatically increases risk: 15–20× higher progression to active TB. TB is curable with standardized multi-drug regimens, but drug resistance (MDR-TB, XDR-TB) is a growing global emergency.
Emergency Signs
Seek medical care promptly if:
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Cough lasting ≥2 weeks, especially with hemoptysis (blood in sputum)
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Unexplained weight loss, night sweats, and persistent low-grade fever
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Neck stiffness with headache and fever (TB meningitis — emergency)
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Difficulty breathing or chest pain after prolonged cough
Seek EMERGENCY care if:
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Massive hemoptysis (large amount of blood coughed up)
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Severe headache with confusion, vomiting, and photophobia
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Sudden weakness or paralysis of limbs (spinal TB compression)
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Signs of sepsis: high fever, rapid pulse, confusion, low blood pressure
Detailed Symptoms
Most common signs and symptoms
Latent TB infection (LTBI):
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Asymptomatic; not infectious
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Positive tuberculin skin test (TST/Mantoux) or interferon-gamma release assay (IGRA)
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Normal chest X-ray (or calcified granuloma)
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Identified through screening contacts, immigrants, healthcare workers
Active pulmonary TB (classic presentation — insidious onset over weeks):
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Chronic cough lasting ≥2–3 weeks (initially dry, becoming productive)
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Hemoptysis (blood in sputum — may range from blood-streaked to frank hemorrhage)
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Night sweats (drenching, requiring change of bedclothes)
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Unintentional weight loss and anorexia
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Low-grade fever (often afternoon/evening pattern)
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Fatigue and malaise
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Chest pain (pleuritic)
Extrapulmonary TB (~15% of cases; higher in HIV+):
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TB lymphadenitis: Painless cervical lymph node enlargement (scrofula); most common extrapulmonary form
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TB meningitis: Gradual onset headache, fever, cranial nerve palsies, confusion — medical emergency
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Skeletal TB (Pott disease): Vertebral body destruction, paravertebral abscess, kyphosis
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Miliary TB: Disseminated disease with diffuse tiny nodules on CXR; fever, hepatosplenomegaly, multiorgan involvement; may present acutely in immunocompromised
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Genitourinary TB: Sterile pyuria, hematuria, epididymitis, infertility
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Pericardial TB: Pericardial effusion, constrictive pericarditis
Knowing the symptoms is the first step to a quick response.
Course of Disease
Typical disease course:
- Primary infection: Inhalation of M. tuberculosis bacilli → primary complex in lungs. Most individuals (90%) contain the infection → latent TB infection (LTBI). Asymptomatic, TST/IGRA positive.
- Latent TB (months to decades): No symptoms, not infectious. Bacilli survive dormant in granulomas.
- Reactivation / active TB: Insidious onset over weeks to months:
- Chronic productive cough (>2–3 weeks), hemoptysis (10–20%).
- Constitutional symptoms: night sweats, fever, weight loss, fatigue.
- Upper lobe cavitary disease on chest X-ray (classic finding).
- Progressive disease (untreated): Cavitation, bilateral disease, endobronchial spread. Cachexia ("consumption"). Miliary dissemination or extrapulmonary TB (lymph nodes, pleura, bones, meninges, genitourinary) in immunosuppressed.
Infectivity: Sputum smear-positive patients are most infectious. Infectivity drops dramatically within 2 weeks of effective treatment.
Diagnosis
How this disease is identified
Active pulmonary TB:
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Sputum smear microscopy (Ziehl-Neelsen): 3 samples (including early morning); sensitivity ~60% for smear-positive TB. Quick and cheap; remains backbone in resource-limited settings.
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GeneXpert MTB/RIF Ultra (Xpert): Automated nucleic acid amplification test (NAAT); sensitivity ~88% (higher than smear); detects rifampicin resistance in 2 hours. WHO-endorsed as initial diagnostic test.
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Sputum culture (Löwenstein-Jensen or MGIT liquid): Gold standard; 10–42 day turnaround; essential for drug susceptibility testing (DST). Sensitivity >80%.
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Chest X-ray: Upper lobe infiltrates, cavitation, hilar lymphadenopathy (primary TB); miliary pattern in disseminated TB. Not specific — must be combined with microbiological confirmation.
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Drug susceptibility testing (DST): Mandatory for all culture-positive cases; line-probe assay (LPA) for rapid rifampicin + isoniazid resistance detection.
Latent TB:
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Tuberculin skin test (TST/Mantoux): Intradermal injection; read at 48–72 hours; ≥5 mm (HIV+, contacts), ≥10 mm (high-risk groups), ≥15 mm (no risk factors). False positive with BCG vaccination.
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IGRA (QuantiFERON-TB Gold Plus / T-SPOT.TB): Blood test; not affected by BCG; preferred for BCG-vaccinated populations.
TB meningitis: CSF shows lymphocytic pleocytosis, very high protein, very low glucose; Xpert from CSF (sensitivity ~70%); culture essential.
Treatment
Available treatment methods
Active drug-susceptible TB (WHO standard regimen):
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Intensive phase (2 months): Rifampicin + Isoniazid + Pyrazinamide + Ethambutol (RHZE) — daily
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Continuation phase (4 months): Rifampicin + Isoniazid (RH) — daily
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Total: 6 months for pulmonary TB; 9–12 months for TB meningitis and bone TB
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Directly Observed Therapy (DOT): WHO recommends treatment observation to ensure adherence and prevent resistance
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Pyridoxine (Vitamin B6): Co-prescribe with isoniazid to prevent peripheral neuropathy
MDR-TB (resistant to rifampicin + isoniazid):
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BPaL regimen (Bedaquiline + Pretomanid + Linezolid): 6 months; WHO-recommended since 2022; cure rate ~89%
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Alternatively: 9–18 month regimen with bedaquiline, fluoroquinolone, linezolid, clofazimine, cycloserine
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Requires specialist management and monitoring (hepatotoxicity, QT prolongation, optic neuritis)
XDR-TB (MDR + fluoroquinolone resistance):
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BPaL-based regimen; individualized DST-guided treatment; 18–24 months historically; newer regimens shorter
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Mortality remains high (30–50% historically; improving with BPaL)
Latent TB treatment (preventive therapy):
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3HP: Rifapentine + isoniazid weekly × 3 months (WHO preferred; 12 doses total)
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4R: Rifampicin daily × 4 months
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6H or 9H: Isoniazid daily × 6 or 9 months (older regimens; more hepatotoxicity)
Monitoring: Monthly sputum cultures until conversion; liver function tests (baseline + monthly for first 2 months); visual acuity for ethambutol.
Most cases are effectively treated with early diagnosis.
Prevention Details
How to protect yourself
BCG Vaccination:
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Bacillus Calmette-Guérin (BCG) — live attenuated M. bovis vaccine
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Given at birth or shortly after in endemic countries; single dose (no booster)
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Efficacy: 70–80% protection against severe childhood TB (miliary, meningitis); highly variable (0–80%) against adult pulmonary TB
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Does NOT prevent infection or eliminate LTBI — prevents progression to severe disease in children
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NOT routinely recommended for travelers — considered only for children <5 years with prolonged exposure in high-burden settings
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BCG causes positive TST (but NOT positive IGRA) — use IGRA for screening BCG-vaccinated individuals
Infection control:
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Respiratory isolation for smear-positive pulmonary TB patients
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N95 respirator for healthcare workers in TB settings
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Ventilation and UV germicidal irradiation in healthcare facilities
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Latent TB screening for close contacts (window period: 8–10 weeks for TST conversion)
TB preventive treatment for travelers:
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Post-travel LTBI screening recommended for travelers with ≥3 months cumulative time in high-burden countries (or significant healthcare/congregate setting exposure)
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Pre-travel baseline TST/IGRA for comparison
Preparation is the best protection.
Travel Advice
Risk to travelers:
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High risk: Prolonged stays (≥3 months) in high-burden countries (South and Southeast Asia, Sub-Saharan Africa)
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Moderate risk: Healthcare workers, volunteers in TB clinics/hospitals, prison visitors, refugee camp workers
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Lower risk: Short-term tourism in standard accommodations
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Pre-travel: – Baseline TST or IGRA (to enable post-travel comparison) – BCG is NOT recommended for adult travelers (poor efficacy for pulmonary TB; interferes with TST screening) – N95 masks for healthcare settings in high-burden areas
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During travel: – Avoid prolonged close contact in crowded, poorly ventilated spaces (public transport, shelters) – Healthcare volunteers should follow infection control protocols
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Post-travel: – Repeat TST/IGRA at 8–10 weeks after return if ≥3 months in high-burden country – If conversion detected: chest X-ray + consider preventive therapy (3HP or 4R) – Seek evaluation for persistent cough (≥2 weeks), night sweats, weight loss, hemoptysis
How common is it?
Statistics and geographic data
TB remains the world's deadliest infectious disease (surpassing COVID-19 since 2023):
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Global burden (2023 WHO report): 10.8 million new cases, 1.25 million deaths (including ~167,000 HIV-associated TB deaths)
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Top 8 countries (75% of global burden): India (27%), Indonesia (10%), China (7%), Philippines (7%), Pakistan (6%), Nigeria (5%), Bangladesh (4%), Democratic Republic of Congo (4%)
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HIV-TB co-infection: TB is the leading killer of people with HIV; ~6.2% of new TB cases are HIV-positive (highest in Africa: 27%)
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Drug resistance: ~410,000 MDR/RR-TB cases in 2023; highest rates in former Soviet states (up to 35% of new cases in some countries)
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Latent TB: ~25% of the world's population has LTBI (~2 billion people); vast reservoir for future active disease
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Treatment gap: Only 7.5 million of 10.8 million were diagnosed and treated in 2023 (30% missing)
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Economic impact: TB causes estimated $12 billion/year in lost productivity; catastrophic costs affect 48% of TB-affected households
Incidence is declining ~2%/year globally — far below the 10%/year needed to meet WHO End TB 2035 targets.
Risk Factors
Who is most at risk
Travel to high-burden countries (Southeast Asia, Sub-Saharan Africa, Western Pacific), HIV co-infection, immunosuppressive therapy, close contact with active TB cases, healthcare workers, residents of congregate settings (shelters, prisons), malnutrition, diabetes, smoking, silicosis.
Complications Details
Potential complications
TB is the leading infectious disease killer globally:
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Mortality (active TB): 1.25 million deaths in 2023 (WHO)
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case fatality 10–40% without treatment (drug-susceptible)
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30–50% for MDR/XDR-TB historically
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Drug resistance: MDR-TB: ~410,000 new cases/year (2023 WHO)
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XDR-TB emerging globally
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treatment is prolonged, expensive, and has more side effects
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Hemoptysis: Massive hemoptysis (>600 mL/24h) from bronchial artery erosion — life-threatening
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requires bronchial artery embolization or surgery
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Destroyed lung: Extensive fibrosis, bronchiectasis, aspergilloma (fungal ball in cavities) — chronic respiratory insufficiency
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TB meningitis complications: Hydrocephalus, stroke (vasculitis), cranial nerve palsies, cognitive disability
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mortality 20–50% even with treatment
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Pott disease: Vertebral collapse, spinal cord compression, paraplegia
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Immune reconstitution inflammatory syndrome (IRIS): In HIV+ patients starting ART
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paradoxical worsening of TB symptoms
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Drug side effects: Hepatotoxicity (RHZ), optic neuritis (ethambutol), peripheral neuropathy (isoniazid), thrombocytopenia (rifampicin), QT prolongation (bedaquiline)
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Post-TB lung disease: ~50% of successfully treated patients have residual lung impairment (obstructive, restrictive, or mixed pattern)
Recovery & Outlook
Expected outcomes and recovery
Latent TB: 5–10% lifetime risk of reactivation in immunocompetent individuals. Treatment with isoniazid (9 months) or rifampin (4 months) reduces reactivation risk by 60–90%.
Drug-susceptible pulmonary TB:
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With standard 6-month treatment (2HRZE/4HR): cure rate >95%.
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Without treatment: ~50% die within 5 years, ~25% spontaneously resolve, ~25% become chronically ill.
Drug-resistant TB:
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MDR-TB (resistant to isoniazid + rifampin): treatment duration 9–20 months, cure rate 50–75%.
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XDR-TB: cure rate 30–50% with newer agents (bedaquiline, pretomanid, linezolid).
Extrapulmonary TB: Prognosis depends on site. TB meningitis has 20–30% mortality and significant neurological morbidity.
