The specific time it takes for TB to have visible lesions is significantly related to the patient’s own resistance, the number of infected TB bacteria and the virulence. If the patient’s resistance to TB infection is weak and the number of infected TB bacilli is high or the virulence is strong, the lung lesions are usually evident in about four weeks, but if the patient’s resistance is strong, there may be no clinical manifestations even if the patient is sometimes infected with TB bacilli. When the resistance of the organism decreases again, symptoms of tuberculosis as well as imaging manifestations may appear. Some patients usually start to have visible lesions only after months or years, while some patients may not develop the disease for life after infection with the tubercle bacillus.