After the cure of tuberculosis, there is no infectiousness, no clinical symptoms, only old tuberculosis lesions, and the physical examination can be passed. Old foci of pulmonary tuberculosis can be seen as isolated or multiple calcified foci, or sclerotic foci, and foci with cords, clear margins or purified cavities, or pleural thickening, adhesions or calcifications. Patients with pulmonary tuberculosis, through standardized anti-tuberculosis treatment, generally disappear their symptoms in about two weeks and are not infectious. The source of TB infection is mainly sputum-carrying patients. TB patients can spread microdroplets of Mycobacterium tuberculosis into the air through coughing, sneezing, talking, laughing, etc., and can survive in the air for several hours, which can cause infection after being inhaled by others.