What is the hallmark symptom of tuberculosis?

The hallmark symptom of tuberculosis (TB) is a persistent cough lasting more than three weeks. This symptom is significant because it reflects the chronic nature of the infection, which primarily affects the lungs when it is pulmonary tuberculosis. The cough may produce sputum, which can sometimes be blood-tinged, and its duration is what typically alerts health professionals to consider TB as a potential diagnosis.

Other symptoms of TB may include fever, night sweats, fatigue, and weight loss, but the persistent cough is the most characteristic sign that leads to further investigation and diagnosis. In the context of TB, while high fever, chills, chest pain, and shortness of breath can occur, they are not as defining for the disease as the prolonged cough. Hence, the presence of a cough lasting more than three weeks serves as a key indicator for clinicians to suspect tuberculosis and conduct appropriate testing.