At the beginning of the disease, there are often general flu symptoms, such as sudden onset, cough, sore throat, accompanied by fever, headache, myalgia, and discomfort. The symptoms continue to progress, with persistent high fever, shortness of breath, cyanosis, paroxysmal cough, and hemoptysis. The sputum volume is often small, but it may contain blood. Secondary bacterial infection often occurs within 2 weeks of onset, manifested as high fever or symptoms that are relieved once and then worsened again. The sputum becomes purulent, and symptoms and signs of bacterial pneumonia appear. The pathogens are mostly Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, etc. Influenza virus pneumonia is common in patients with chronic heart and lung diseases, chronic metabolic diseases, and chronic kidney disease, leading to the deterioration of the underlying disease. Chest X-ray examination shows inflammatory infiltration from the hilum to the periphery at the beginning of the disease, followed by scattered flakes and flocculent shadows, which are often distributed in multiple lung fields. In the late stage, it presents a fusion change, mostly concentrated in the inner and middle zones of the lung fields, similar to pulmonary edema. The diagnosis of influenza virus pneumonia depends on the onset and typical clinical manifestations during the influenza epidemic, the isolation of influenza virus from sputum and other secretions and lung tissue, and the exclusion of bacterial and other pathogenic infections such as meningococcal meningitis, Legionnaires' disease, mycoplasma pneumonia, etc. The diagnosis of secondary bacterial pneumonia can be confirmed by bacterial culture of sputum, lung tissue, pleural effusion, blood and other specimens.