Pneumonia can also be diagnosed in elderly people with normal white blood cells, for example, but with a significant inflammatory infiltrate on lung CT, and cannot be determined solely by an elevated or decreased blood count. The clinical diagnosis of pneumonia depends on a combination of clinical symptoms, physical examination, and ancillary tests. If the patient has respiratory symptoms such as cough, sputum, fever, etc., and dry or wet rales are detected in the lungs, and the chest radiograph or lung CT shows an inflammatory infiltrate, the diagnosis of pneumonia can be confirmed clinically. After the diagnosis of pneumonia is confirmed, we need to evaluate the causative organism, and the treatment of different causative organisms is also different. For bacterial infections, we need to treat with antibiotics; for viral infections, we need to use antipyretic or antiviral drugs; for atypical pathogens, we need to use macrolide antibiotics or quinolone antibiotics.