I. Air-respiratory. This is the most important way of transmission of tuberculosis. If a patient speaks loudly, coughs or sneezes, many droplets with tuberculosis bacilli will be released, and if a susceptible person inhales such droplets, he or she can be infected. If a tuberculosis patient spits on the ground, the sputum will dry and the tuberculosis bacilli will be mixed with dust in the air and inhaled by a healthy person, which can also cause infection. Second, the digestive tract infection. The tableware and leftover food used by TB patients may be contaminated with Mycobacterium tuberculosis. Drinking unsterilized milk or dairy products can also infect bovine tuberculosis bacilli and cause intestinal tuberculosis. Third, mother-to-child transmission. When a mother with TB disease is pregnant, the TB bacillus in her body can enter the fetus through the blood of the umbilical cord, and the fetus can be infected by swallowing or inhaling the amniotic fluid containing TB bacillus, thus developing congenital TB disease.