Influenza viruses enter the body mainly by the mouth and nose during breathing and invade the nose, throat and pharynx causing inflammation. Influenza viruses are generally spread through airborne droplets, contact between susceptible and infected persons, or contact with contaminated objects. The incubation period of upper respiratory tract infection is short, and the onset of the disease is rapid. Early symptoms such as dry or sore throat often appear, followed by nasal congestion, runny nose, sneezing and coughing. After entering the respiratory mucosa epithelium through the nose and mouth, the influenza virus can reduce the viscosity of the respiratory mucus layer, infect some respiratory epithelial cells, replicate and proliferate in the cells, resulting in vacuolation and degeneration of the epithelial cells, and finally cell lysis and death, and within a few hours, rapidly produce daughter virions to spread to neighboring cells, thus repeating the virus proliferation cycle. Therefore, it is important to avoid crowded places during the high influenza virus season, wear masks when going out, and wash hands, disinfect and ventilate as often as possible.