People who live or work in the same environment may be infected with TB bacteria at the same time, but being infected with TB bacteria does not mean that you have TB disease. Here there is a problem of “war” between TB bacteria and people. Since it is a “war”, there are two scenarios: one is that people overcome the TB bacillus and do not get sick, and the other is that the TB bacillus “sets up camp and grows and multiplies” in the human body and people get sick. The normal human body has resistance, and in a healthy state, the human body can resist many pathogenic microorganisms such as bacteria, viruses and mycoplasma. However, if the body’s resistance decreases, the tubercle bacilli will “take advantage of the situation” and cause lesions in the body.