In the first infection of tuberculosis, also called primary tuberculosis, the symptoms are relatively mild or even asymptomatic, plus it is difficult to detect because it has healed itself. If Mycobacterium tuberculosis infects the human body for the first time, the body’s immune system will eliminate most of the Mycobacterium tuberculosis, which will stop the reproduction of Mycobacterium tuberculosis in the body and only a small amount of Mycobacterium tuberculosis remains, and most of the Mycobacterium tuberculosis that has not been eliminated will remain dormant for a long time. The symptoms of primary tuberculosis may only be coughing, coughing up sputum, or even no symptoms, and there may not be any physical signs when the lesion is small, and this process is easy to be ignored, and the primary tuberculosis may be cured by itself after a period of time. After a long period of dormancy of Mycobacterium tuberculosis, there are no symptoms to reoccur. Infection with Mycobacterium tuberculosis can be detected when a PPD test is done, or when a chest X-ray reveals old TB lesions. If there are further symptoms such as low-grade fever and cough, it may be secondary tuberculosis. You should go to the hospital as soon as possible for treatment under the supervision of a doctor.