Tuberculosis is a contagious disease, and hearing the term "tuberculosis" inevitably makes people nervous. However, not all tuberculosis patients are contagious. Research shows that among tuberculosis patients, only those who have tuberculosis bacteria found in sputum smear tests are contagious. With a source of infection, the tuberculosis bacteria must be transmitted to others through certain routes. Airborne transmission is the main route of transmission for tuberculosis bacteria. When a tuberculosis patient coughs, sneezes, or speaks loudly, they release a large number of droplet nuclei containing tuberculosis bacteria into the air, which can be inhaled by healthy individuals and cause infection. The degree of tuberculosis bacteria infection mainly depends on factors such as the amount of bacteria the patient expels, the severity of coughing symptoms, and the extent of contact. Therefore, when there is a tuberculosis patient nearby, we first need to understand whether they are in the active phase of the disease, that is, expelling bacteria, and whether they are undergoing anti-tuberculosis chemotherapy. If the patient has a negative sputum test or has undergone chemotherapy for a positive sputum test, such patients have very low contagiousness, so there is no need to worry too much about being infected.