Tuberculosis is a chronic infectious disease caused by Mycobacterium tuberculosis. Patients with disseminated tuberculosis are an important source of infection. Mycobacterium tuberculosis is transmitted mainly through the respiratory tract. Mycobacterium tuberculosis is relatively resistant to dryness, cold, acid and alkali. Can tolerate cold, even if the cold to the freezing point, can not kill it, -6 ℃ – 8 ℃ environment class survival 4-5 years. Some physical and chemical methods can kill it, such as boiling for 10 minutes, sunlight or ultraviolet radiation for 2-7 hours, spitting spit on paper and burning it, 70-75% alcohol contact for 3-5 minutes, 1-2% phenol contact for 1-5 minutes. Since tuberculosis is a contagious disease, we have to learn to prevent it. Preventive measures for tuberculosis 1. Control the source of infection The main source of infection of tuberculosis is secondary tuberculosis patients. Since Mycobacterium tuberculosis is mainly disseminated with sputum out of the body, patients with Mycobacterium tuberculosis detected in sputum are infectious and are the source of infection. The degree of infectiousness depends on the amount of bacilli in the sputum. If sputum-positive patients receive early and rational chemotherapy, the number of Mycobacterium tuberculosis in the sputum is reduced, and its viability is also reduced or lost. The most dangerous sources of TB infection are those smear-positive patients who are undetected and not managed or treated appropriately. Therefore early detection of patients, especially those who are bacteriologically positive, and timely administration of rational chemotherapy is a central part of modern anti-TB efforts. Early detection of patients is achieved by timely X-ray chest radiographs and bacteriological examinations of suspected patients. 2. Cut off the infection route TB is mainly transmitted through the respiratory tract (coughing, sneezing, laughing, talking loudly, etc.), so spitting is prohibited. The sputum, daily necessities and things around the bacterium-positive patients should be disinfected and handled appropriately. 3, protection of susceptible groups Infants and children with imperfect cellular immune systems, the elderly, HIV-infected patients, immunosuppressant users, patients with chronic diseases and other immune deficiencies are susceptible groups of tuberculosis. (1) Vaccination with BCG vaccine, a non-pathogenic live vaccine, can give specific immunity to TB to those who are not infected with TB. (2) Improve the ability to resist infection and self-protection, establish good hygiene and living behavior habits, do not smoke, do not drink, bathe regularly, ensure adequate sleep, balanced diet, reasonable nutrition, strengthen physical exercise, prevent colds and flu, reasonable use of antibiotics; reduce contact with tuberculosis patients, visiting patients should take preventive measures such as with the permission of the doctor or with a mask.