Which statement correctly differentiates latent TB infection from active TB disease in terms of symptoms and contagion?

• A. Latent TB is highly contagious; active TB is not contagious.
• B. Latent TB infection has Mycobacterium tuberculosis infection without symptoms and is not contagious; active TB presents with symptoms (cough, fever, night sweats, weight loss) and is contagious.
• C. Latent TB always requires immediate isolation, while active TB does not.
• D. Both latent and active TB are equally contagious.

Answer: (B)

The key distinction is that latent TB infection means the bacteria are present but dormant—there are no symptoms and the person is not contagious. Active TB disease means the bacteria are actively multiplying, causing symptoms such as a persistent cough, fever, night sweats, and weight loss, and the person can spread the infection to others through airborne droplets. This combination—no symptoms and noncontagious for latent TB, versus symptoms and contagiousness for active TB—explains why the correct statement describes latent infection as asymptomatic and noncontagious and active disease as symptomatic and contagious. Latent TB is usually detected by a positive TB skin test or IGRA with a normal chest X-ray and no illness, and treatment aims to prevent reactivation. Active TB requires prompt diagnosis, isolation in settings with airborne precautions, and a multi-drug treatment regimen.