Respiratory transmission is the most important mode of transmission of TB. During pregnancy, the tuberculosis bacilli in the mother’s body can enter the fetus through the blood of the umbilical cord, and the fetus can also become infected by swallowing or inhaling amniotic fluid containing tuberculosis bacilli. There are three most common routes of transmission of TB: First, airborne-respiratory transmission is the primary mode of transmission of TB. Mycobacterium tuberculosis bacteria are present in foci of TB in the lungs and bronchi, or in the lung space and sputum of secretions from the trachea. When a patient speaks loudly and coughs or sneezes, many tiny droplets are released. The patient can release 3,500 droplets in one cough, and even more when sneezing hard. Only those droplets with a diameter of 5-10 microns can float in the air for a long time, and if a susceptible person inhales such droplets with Mycobacterium tuberculosis, he can be infected. In addition, spitting infection is also an important route of infection, if a person with tuberculosis spits out sputum containing mycobacterium tuberculosis on the ground, the sputum dries, the mycobacterium tuberculosis in the sputum and dust mixed together, flying in the air, can be inhaled by healthy people to cause infection. Second, food transmission. The tableware and leftover food used by TB patients may be contaminated with Mycobacterium tuberculosis, such as sharing tableware with TB patients or eating leftover food from patients, or eating vegetables and drinking soup in a bowl, etc. Mycobacterium tuberculosis may be introduced through diet. Drinking unpasteurized milk or dairy products can also infect bovine Mycobacterium tuberculosis. If you pour a sputum jar for a patient with bacillus excretion and accidentally get sputum on your hands, you may also get infected if you do not wash your hands carefully and eat food with your hands. Some women like to feed their babies by chewing food with their mouths, so if she is a TB-excreting patient, the baby is likely to be infected. In general, the digestive tract is more resistant to Mycobacterium tuberculosis. Once Mycobacterium tuberculosis enters the stomach, it is easily killed by a large amount of stomach acid, so it is not easy to get infected unless a large amount of Mycobacterium tuberculosis is swallowed. Most cases of digestive tract tuberculosis are caused by drinking unboiled milk. Third, vertical transmission. The fetus can also be infected by swallowing or inhaling amniotic fluid containing tuberculosis bacteria, which can cause congenital tuberculosis in the fetus. Dr. Zhou pointed out that in addition to the above-mentioned modes of infection, Mycobacterium tuberculosis can also be directly infected by wounds on the skin or mucous membranes. In addition, tuberculosis is a zoonotic disease, many animals such as pigs, cats, dogs, cattle, sheep, monkeys, etc. can suffer from tuberculosis, humans and these animals are often in contact, can also be infected by animals suffering from tuberculosis, or infect their own tuberculosis to the animals they keep. People with tuberculosis should do the following: 1. Do not face others when coughing, sneezing or laughing loudly, and cover your mouth with a handkerchief; 2. Do not share the same head when sleeping to avoid infection during the night when coughing; develop good hygiene habits and do not spit; 3. Use a single bowl and chopsticks; wash and dry bedding frequently. Healthy people should: be relatively isolated from people with tuberculosis in the infectious period, avoid talking with people with tuberculosis face to face in close proximity, do not eat food left over from people with tuberculosis, and wash hands carefully with soap after emptying sputum cans.