Tuberculosis (TB)

Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis. It most often affects the lungs (pulmonary TB) but can involve any organ. TB spreads through the air when a person with active pulmonary TB coughs, sneezes, or speaks.

Not everyone infected becomes sick. Latent TB infection means the bacteria are present but inactive and cause no symptoms; it is not contagious. Active TB disease causes illness and can be transmitted. Both latent infection and active disease are treatable with antibiotics. Drug-resistant TB requires specialized regimens. Global control depends on case detection, complete treatment, infection control, and addressing social determinants.

Active pulmonary TB may cause:

• A cough lasting three weeks or longer
• Coughing up blood or sputum
• Chest pain
• Unintentional weight loss
• Fatigue
• Fever and night sweats
• Chills
• Loss of appetite

Extrapulmonary TB symptoms depend on the site (lymph nodes, bones, kidneys, brain/meninges, etc.). Latent TB has no symptoms. People with HIV or other immunocompromise may have atypical presentations.

TB is caused by Mycobacterium tuberculosis complex organisms. Transmission is airborne via droplet nuclei from people with active respiratory TB. Close, prolonged indoor contact poses the highest risk. After inhalation, the bacteria may be cleared, contained as latent infection, or progress to primary active disease. Reactivation of latent infection years later accounts for many adult cases, especially when immunity wanes.

Higher risk of infection or progression to disease includes:

• Close contact with someone who has active TB
• Living or working in high-prevalence settings (certain countries, correctional facilities, homeless shelters)
• HIV infection (strongest risk factor for progression)
• Immunosuppressive medicines or conditions (TNF inhibitors, transplant, silicosis, diabetes, severe kidney disease, head and neck cancer)
• Malnutrition and smoking
• Young children and older adults
• Injection drug use

Untreated active TB can cause severe lung damage, spread to other organs, and death. TB meningitis and miliary TB are life-threatening forms. Drug resistance (MDR-TB, XDR-TB) complicates treatment and outcomes. Treatment itself can cause side effects, including liver toxicity and, with some second-line drugs, hearing or psychiatric effects.

Prevention strategies include:

• Early detection and complete treatment of active TB to stop transmission
• Treatment of latent TB infection in people at elevated risk of progression
• Infection control (ventilation, isolation of infectious patients, protective equipment)
• BCG vaccine in infants in high-burden countries (limited efficacy against adult pulmonary TB)
• Addressing HIV, malnutrition, and crowded living conditions
• Screening high-risk populations

Evaluation for active TB may include:

• Medical history and physical examination
• Chest X-ray
• Sputum smear microscopy, nucleic acid amplification tests (e.g., Xpert MTB/RIF), and culture with drug-susceptibility testing
• Imaging and sampling of extrapulmonary sites when indicated

Latent TB is diagnosed with a tuberculin skin test (TST) or interferon-gamma release assay (IGRA), after active disease is excluded. Interpretation depends on risk factors and BCG history.

See a clinician for a cough lasting more than three weeks, especially with fever, night sweats, or weight loss, or after known exposure to someone with active TB. People with HIV, on immunosuppressants, or with other risk factors should discuss TB screening with their care team.

Active drug-susceptible TB — standard multi-drug regimens (typically isoniazid, rifampin, pyrazinamide, and ethambutol in an intensive phase, then isoniazid and rifampin) for about 6 months; shorter regimens are available in some guidelines for selected patients. Directly observed therapy improves completion rates.

Drug-resistant TB — individualized regimens using later-generation medicines (bedaquiline, pretomanid, linezolid, fluoroquinolones, and others) under specialist care; duration is longer.

Latent TB infection — shorter rifamycin-based regimens (e.g., 3HP, 4R) or isoniazid for 6–9 months, chosen by age, comorbidities, and drug interactions.

Monitoring for adherence, response, and drug toxicity is essential. HIV coinfection requires coordinated antiretroviral and TB therapy.

During treatment:

• Take every dose as prescribed; incomplete treatment risks relapse and resistance
• Attend all clinic and laboratory monitoring visits
• Report side effects (especially jaundice, severe fatigue, vision changes, neuropathy) promptly
• Cover coughs; follow isolation guidance until declared non-infectious
• Avoid alcohol to reduce liver strain from medicines
• Support household contact evaluation and preventive treatment when recommended

Bring:

• Symptom timeline and any known TB exposures or travel
• HIV status and other medical conditions
• Complete medication list (critical for drug-interaction checking with rifamycins)
• Prior TB test or treatment history
• Questions about regimen duration, side effects, isolation, and protecting household members