Understanding Tuberculosis Transmission: How Is TB Spread?

Tuberculosis (TB) is caused by Mycobacterium tuberculosis. Transmission occurs almost exclusively via airborne droplet nuclei (1–5 µm) generated when a person with active pulmonary or laryngeal TB coughs, sneezes, speaks, or sings.

Key Transmission Facts

• Not spread by: Touching, sharing utensils, kissing, food, water, blood (rare), casual contact (elevator, bus, brief conversation).
• Requires: Prolonged, close contact in enclosed, poorly ventilated spaces (hours, not minutes).
• Infectiousness correlates with: Sputum smear positivity, cavitary disease, cough frequency, lack of treatment.
• Effective treatment rapidly reduces transmission: Most patients non-infectious after 2 weeks of appropriate therapy.

High-Risk Settings

• Household contacts
• Healthcare facilities (especially before diagnosis)
• Correctional facilities, homeless shelters, refugee camps
• Immunocompromised populations (HIV)

Prevention

• Early diagnosis & treatment (cough >2 weeks → sputum GeneXpert/AFB).
• Respiratory isolation (negative pressure room, N95 for staff, surgical mask for patient).
• Ventilation, UVGI.
• Contact investigation & latent TB infection (LTBI) treatment.
• BCG vaccine (limited efficacy against pulmonary TB in adults).

Latent TB infection (LTBI) is not contagious; only active disease transmits.