Which is one phase of primary TB?

• A. Primary Infection
• B. Latent TB Infection
• C. Active TB Disease
• D. Reactivation TB

Answer: (A)

The first event after inhaling Mycobacterium tuberculosis is the primary infection. This phase marks the initial establishment of infection in the lungs and nearby lymph tissue. Often it causes no symptoms because the immune system walls off the bacilli within granulomas, and you may see a localized lesion called a Ghon focus, potentially part of a Ghon complex. This stage is distinct from latent TB infection, where the bacteria remain dormant without illness or transmission, and from active TB disease or reactivation TB, which describe later progression when the bacteria become active or reactivate after dormancy. So identifying primary infection as the phase fits the initial, first-infection stage of TB.