Tuberculosis that is cured without medication may come back later. More than 90% of tuberculosis cases are caused by Mycobacterium tuberculosis, and TB is mainly spread by droplets carrying Mycobacterium tuberculosis. The first infection of TB is usually called primary TB, and its recovery depends on the virulence of the infecting Mycobacterium tuberculosis and the strength of the body’s own immunity, and the Mycobacterium tuberculosis may not completely disappear from the body after recovery. When the body’s immune system declines, such as malnutrition and other diseases, resulting in weak resistance and impaired autoimmune function, there is a possibility of relapse through the following two ways: 1. Relapse caused by reactivation of the original TB foci in the body. 2. secondary tuberculosis caused by re-exposure to externally transmitted tuberculosis bacilli. Warm reminder: for patients who have been infected with tuberculosis in the past, they should actively exercise, enhance physical fitness, improve immunity, and consult the doctor in time if there is any discomfort.