Which statement differentiates latent TB infection from active TB disease?

• A. Latent TB infection is asymptomatic and cannot transmit; Active TB is symptomatic and contagious
• B. Latent TB infection is symptomatic; Active TB is asymptomatic
• C. Both latent and active TB cannot transmit
• D. Active TB cannot be diagnosed with TST

Answer: (A)

Latent TB infection means the bacteria are present but kept in check by the immune system. The person feels fine, has no symptoms, and cannot transmit the infection to others. Active TB disease, on the other hand, presents with symptoms such as a persistent cough, fever, night sweats, and weight loss, and the person is contagious, spreading bacteria through airborne droplets. A positive TB test (TST or IGRA) can occur in both states, so these tests don’t by themselves distinguish latent infection from active disease. Diagnosis relies on evaluating symptoms plus chest imaging and microbiologic findings (like sputum smear or culture) to determine whether the disease is active. This difference in symptoms and contagiousness is what differentiates latent TB from active TB.