Which symptom is most characteristic of active tuberculosis?

• A. Weight gain
• B. Absence of fever
• C. Persistent cough for more than 2-3 weeks
• D. Improved energy

Answer: (C)

Persistent cough that lasts more than two to three weeks is the hallmark of active tuberculosis. TB in the lungs triggers ongoing inflammation and mucus production, so the cough becomes a sustained symptom rather than a short-lived one like many other respiratory illnesses. The duration helps distinguish TB from acute infections such as a common cold or typical bronchitis, which usually improve within days to a couple of weeks.

Weight gain is not typical; active TB more often causes weight loss due to decreased appetite and systemic illness. Absence of fever isn’t a reliable clue, since fever can occur with TB (often low-grade), and some people may not have it at all. Improved energy would suggest recovery, not an active infection.