Secondary TB is best described as:

• A. An active infection occurring after latent TB, often with upper-lobe cavitation
• B. A dormant infection with no symptoms
• C. A mild bronchitis unrelated to TB
• D. An infection limited to extrapulmonary sites only

Answer: (A)

Secondary TB, or reactivation TB, is an active infection that emerges when latent TB becomes active again, often years after the initial infection. The bacilli persist in a dormant state within granulomas and resume multiplication when immune containment wanes. It typically involves the upper lobes of the lungs where oxygen tension is higher, and cavitation can develop due to caseous necrosis, creating highly infectious lesions. Clinically you may see cough, night sweats, weight loss, and sometimes coughing up blood. This fits best because latent TB is asymptomatic, and a mild bronchitis or an infection limited strictly to extrapulmonary sites does not capture the classic pulmonary cavitary reactivation pattern.