Sputum smear-negative tuberculosis patients are less likely to be contagious with 15 days of treatment. Sputum smear-positive tuberculosis is more contagious, sputum smear-negative tuberculosis is less contagious, and the probability of contagiousness of 15 days of treatment for sputum smear-negative patients is reduced. Generally, sputum smear results are negative for more than 3 different periods of time, proving that the patient is not contagious. It usually takes about 2 months for sputum smear-positive TB patients to achieve this result. Sputum smear-negative people themselves are less infectious, and 15 days of treatment is relatively less infectious. Tuberculosis is a chronic infectious disease that requires prolonged anti-tuberculosis treatment, which usually lasts about 6 months to 1 year, so even if the sputum smear is negative, it is recommended to continue the anti-tuberculosis treatment under the guidance of a doctor.