Which statement best distinguishes latent TB infection from active TB disease?

• A. Asymptomatic and noncontagious vs symptomatic and contagious
• B. Asymptomatic and contagious vs symptomatic and noncontagious
• C. Symptomatic and contagious vs asymptomatic and noncontagious
• D. Asymptomatic and noncontagious vs asymptomatic and contagious

Answer: (A)

The main concept is the difference in symptoms and contagiousness between latent TB infection and active TB disease. In latent TB, the bacteria are present but dormant, so there are no symptoms and the person is not contagious. In active TB disease, the bacteria are actively multiplying, which causes symptoms such as a persistent cough, fever, night sweats, and weight loss, and the person can spread the infection to others through airborne droplets. Therefore, the statement that latent TB is asymptomatic and noncontagious while active TB is symptomatic and contagious best distinguishes the two. The other options mix these features in ways that don’t fit how latent and active TB behave—for example, suggesting contagiousness with latent infection or noncontagiousness with active disease.