Influenza A is influenza, and the disease is spread through infectious sources, transmission routes, and susceptible people. 1. Sources of infection: The influenza population and hidden infected people are the main sources of infection. Influenza viruses are contagious at the end of the incubation period and in the acute stage. Influenza viruses can continue to be detoxified in respiratory secretions for 3-7 days, and for more than 1 week in people with impaired immune function and children. 2. Transmission: Influenza virus can be transmitted through droplet transmission (e.g. sneezing, coughing, etc.), direct contact with mucous membranes through the nasal cavity, mouth, eyes and other infections, or contact with contaminated items indirectly, in confined spaces may be transmitted through aerosols. 3. Susceptible population: Influenza is generally susceptible to the population. The presence of influenza should be actively consulted and reasonably treated under the guidance of a doctor to avoid aggravation of the condition.