Tuberculosis is caused by an infection of the lungs by the bacterium Mycobacterium tuberculosis, and it is a very common infectious respiratory disease clinically. Typically, the early stage of tuberculosis is accompanied by mild fever to varying degrees, usually occurring in the afternoon, along with coughing, expectoration of blood, chest tightness, shortness of breath, and even chest pain, weight loss, fatigue, and night sweats as accompanying clinical symptoms.

In the early stages, the diagnosis of tuberculosis in patients is generally made through these specific clinical symptoms, along with some sputum culture and chest X-ray examinations. Usually, most patients with early-stage tuberculosis will experience symptoms of low-grade fever, but these patients have a characteristic of fever that occurs in the afternoon and does not require antipyretics as it can return to normal by itself in the evening.