The four stages of a cold are divided into the incubation period, the initial stage, the acute stage, and the recovery stage. 1. Incubation period: viruses, bacteria and other pathogenic microorganisms invade the organism, and do not cause clinical symptoms or only have a generalized feeling of weakness, which is called the incubation period of colds. 2. Early stage of cold: After the pathogenic microorganisms invade the body, they cause mild clinical symptoms, such as dry throat, itchy throat, nasal congestion, runny nose, cough, etc. This is the early stage of cold. This is the early stage of a cold. During this period, you should pay attention to rest and drink more warm water. 3. Acute phase of colds: The further development of the early stage of colds enters the acute phase, the symptoms of the onset of this period are more typical, common fever, cough, cough phlegm, sore throat, limb pain, such as the presence of bacterial infection, can appear cough yellow phlegm, yellow nasal discharge and other symptoms. Some patients have serious complications, such as pneumonia, chest pain or dyspnea. 4. Recovery period: After rest and treatment, cold symptoms are relieved and the disease is in recovery.