Influenza incubation period 1 to 3 days, can be as short as 6 hours, as long as 4 days. According to the clinical manifestations can be divided into: 1, typical influenza Acute onset of high fever, chills or chills, headache, body pain, fatigue, loss of appetite and other symptoms of systemic toxicity is obvious while the symptoms of the whistle tract is mild. A few patients may have nasal congestion, runny nose and eye symptoms such as photophobia and lacrimation. Cough, retrosternal discomfort or burning, dry throat and sore throat are also more common. Body temperature may reach 40°C. The face is flushed and the pharynx and outer canthus of the conjunctiva are mildly congested. Dry rales may be present in the lungs. The fever mostly peaks within 1 to 2 days and subsides within 3 to 4 days. After the fever subsides, the inspiratory symptoms are more pronounced and disappear after 3 to 4 days, but malaise can last for 1 to 2 weeks. This type is the most common. Mild type of patients with fever not more than 39 ℃, the symptoms are mild, the duration of the disease 2 to 3 days. 2, influenza virus pneumonia Influenza virus infection can be converted from simple type to pneumonia type, or directly manifested as pneumonia type, pneumonia type is caused by influenza virus infection from the upper whistle tract continues to spread down the whistle tract, primary influenza virus pneumonia is likely to occur in patients with underlying lung and heart disease (especially rheumatic heart disease, patients with left atrial valve stenosis), pregnant women or people in an immunodeficient state, but Up to half of the cases reported have not been confirmed as having underlying disease. The typical onset of pneumonic influenza is characterized by persistent high fever, rapid onset of dyspnea, cyanosis, severe cough, and frothy mucus sputum or blood in the sputum; examination reveals low whistling sounds in both lungs, filled with croup, but no solid signs. The chest X-ray showed scattered flocculent shadows on both sides of the lungs, spreading from the hilum to the periphery; the manifestations were consistent with adult respiratory distress syndrome (ARDS), and the patient could die of heart failure or peripheral circulatory failure. The duration of the disease can be as long as 3 to 4 weeks. Blood gas analysis shows marked hypoxia. Influenza virus can be easily isolated from sputum, and many neutrophilic polynuclear granulocytes can be seen on sputum smear; however, no pathogenic bacteria grow on sputum and blood culture, and antimicrobial therapy is ineffective, and the mortality rate can exceed 50%. Influenza in infants and the elderly often affects the lower whistle, especially when it leads to pneumonia, and about 1/4 of pediatric cases hospitalized for lower whistle infections are caused by influenza viruses. The incidence of influenza pneumonia and bronchiolitis in the elderly increases with age, ranging from 36% in the 60-69 age group to 73% in the 70+ age group. Influenza pneumonia in the elderly often lacks initial symptoms and is easily overlooked. When pneumonia is detected, it is often accompanied by critical conditions such as obvious dehydration, acidosis or impaired consciousness. 3. Toxic and gastrointestinal type Toxic type is extremely rare. The virus invades the neurological and cardiovascular systems and causes toxic symptoms, with clinical signs of encephalitis or meningitis, mainly high fever and coma, often delirium in adults, convulsions in children, and signs of meningeal irritation, and a mild increase in brain crest fluid cell count. Individual cases may have decreased blood pressure or shock due to vascular nervous system disorders or adrenal hemorrhage. Gastrointestinal influenza is common in children, with nausea, vomiting, diarrhea, and abdominal pain as the main symptoms, and recovery usually takes 2 to 3 days.