Tuberculosis is an infectious disease caused by the tuberculosis bacterium. The cause is infection due to inhalation of tuberculosis bacteria contained in the cough of a tuberculosis patient, etc. Among them, those who excrete bacteria in sputum are called infectious tuberculosis. However, there is a big difference between infection and disease onset. Even when infected with TB bacteria, almost most people (80-90%) do not develop the disease. If the disease develops, it is usually within 4-6 months to 2 years after infection. TB disease can be cured with proper treatment (taking anti-TB drugs) within a certain period of time (minimum 6 months). Not all types of TB are contagious. Nor is any person with TB infectious at any time during his or her illness. Relatively speaking, some types of TB are often contagious, while extrapulmonary TB (e.g., bone TB, meningeal TB, etc.) is not contagious. When a bacillus-exhausting patient talks, coughs, sneezes, and other rapid exhalation movements, secretions with tuberculosis bacteria are ejected with the exhalation, forming droplets of varying sizes with varying amounts of bacteria. Particle nuclei containing bacteria are suspended in the air. If the droplets and particles containing bacteria inhaled by healthy people are adsorbed by the mucous membrane of the upper respiratory tract, they can be easily expelled from the body due to coughing caused by the movement of cilia. About 5% of the fine particles containing tuberculosis bacteria can enter the alveoli through the terminal bronchi and cause tuberculosis infection in the lungs. This is causing droplet infection. However, when the patient is cured, he or she is no longer an infectious agent. The easiest and most reliable way to measure and determine whether a patient is infectious is to smear the patient’s sputum and perform a microscopic examination. If the smear is positive for antacid bacilli, the patient is considered infectious, or “infectious”. The most infectious time for infectious tuberculosis is before detection and treatment. Therefore, early detection and proper and timely treatment of the source of infection should be emphasized.