Tuberculosis is not contagious after recovery. After recovering from tuberculosis, the sputum test is negative, and imaging may show calcified lesions, corrugated lesions, or hard nodular lesions, purified cavities, etc. Since the tuberculosis test is negative, no Mycobacterium tuberculosis is spread into the air and is not transmitted to others, but only in active tuberculosis is it transmitted to others. In active tuberculosis, the test is positive for Mycobacterium tuberculosis, so microscopic droplets of Mycobacterium tuberculosis can be spread into the air by coughing, sneezing, talking, laughing, and singing. Therefore, it is important to keep a certain distance and wear a mask for self-protection when in contact with patients with active tuberculosis.