It’s contagious. It belongs to infiltrative pulmonary tuberculosis. When accompanied by large areas of caseous necrosis, it often progresses acutely and has highly toxic symptoms. It often occurs on the basis of exudative or proliferative lesions. If the body's resistance is reduced, the bacterial load is excessive, and the allergic reaction is strong, tuberculosis bacteria in exudative lesions will continue to multiply after defeating macrophages, causing the cells to become cloudy and swollen, then undergo fatty degeneration, dissolve and fragment, until the cells become necrotic. After the death of inflammatory cells, proteolytic enzymes are released, causing tissue dissolution and necrosis, forming coagulative necrosis. Because it contains a large amount of lipids, the lesions appear yellowish-gray under naked eye observation, are loose and brittle, and look like cheese, hence the name caseous necrosis. In primary pulmonary tuberculosis, if the body's immunity is low, such caseous necrosis contains a large number of Mycobacterium tuberculosis, and some of them are expelled from the bronchi to form cavities, which can spread along the airways or blood, causing other types of pulmonary tuberculosis. The most important and effective preventive measure is to minimize contact with tuberculosis patients. In addition to active treatment, patients must also develop good hygiene habits, avoid spitting, and wrap sputum and other respiratory secretions in paper for incineration.