Influenza (influenza for short) is an acute viral respiratory infection. It usually occurs in winter and spring. It mainly occurs in schools, units, factories and public entertainment places where people gather. According to the pathogen is divided into influenza A (influenza A), influenza B, influenza C. Influenza A virus can infect many kinds of animals and is the main pathogen of human influenza. The human population is generally susceptible and has some immunity after the disease. However, there is no cross-immunity between different subtypes. Four pandemics in the 20th century and the 2009 global pandemic were all caused by influenza A viruses. Influenza A is highly contagious and is spread mainly by droplets, but it can also be spread by direct or indirect contact with respiratory secretions and objects of the patient. The symptoms of influenza are usually heavier than those of the common cold, mainly a sudden onset of high fever, chills, headache for 3 to 5 days, and general malaise. Upper respiratory symptoms such as nasal congestion, runny nose, sneezing, etc. are relatively mild or insignificant, and a few cases may have diarrhea with watery stools. The fever subsides after 3 to 5 d, but the patient still feels significantly weak. A small number of patients have only mild upper respiratory symptoms without fever. Signs mainly include pharyngeal congestion and large tonsils. The prognosis of influenza A is good and most patients can recover, but young (less than 5 years old, especially children under 2 years old) and old people, those with pre-existing underlying diseases or immunocompromised, and pregnant women are prone to severe cases of influenza A. These patients are prone to primary influenza virus pneumonia, secondary bacterial pneumonia, and mixed viral bacterial pneumonia. The success rate of resuscitation in critically ill patients is low. School-age children, whose immune function is not fully developed, are also at high risk for influenza A because of the crowded environment in which they live. To prevent influenza A, you should do the following: a. One month before the influenza A epidemic season, you should be vaccinated against influenza A; b. During the influenza A epidemic season, try to avoid crowded places; c. Develop good personal hygiene habits, pay attention to hand hygiene, and use tissues to cover your nose and mouth when coughing and sneezing; d. Keep indoor air circulation; stay away from patients or animals that may be infected with the disease; e. If you come into contact with patients, closely Observe the change of body temperature and go to a specialist hospital as soon as possible for a clear diagnosis of fever; 6. Seven, in the outbreak of influenza A epidemic for susceptible people, especially young children and the elderly can be preventive medicine to prevent influenza A.