Whether or not a tuberculosis infection is contagious depends on three main aspects. i. The number of Mycobacterium tuberculosis bacteria. Second, the virulence of Mycobacterium tuberculosis. Third, the infected person’s own immune status. Second, if the tuberculosis patient after active standardized anti-tuberculosis treatment, the number of mycobacterium tuberculosis excretion is obviously reduced, that is, the virulence of mycobacterium tuberculosis is obviously reduced, and this time is not easy to cause large area infection. Third, if the infected person’s own immune function is reduced, including more underlying diseases, such as chronic obstructive pulmonary disease, diabetes, silicosis workers, etc., these cases are easily infected if infected with Mycobacterium tuberculosis. In conclusion, whether Mycobacterium tuberculosis infection can be transmitted afterwards is closely related to one’s own immune function as well as the number and virulence of the excreted bacteria.