Influenza, also called flu, is caused by influenza viruses, which are categorized into three types: A, B, and C. After infecting a human, symptoms exhibited by a patient include fever, sore throat, cough, and phlegm, which characterizes the disease called influenza. This disease is classified as a Class B infectious disease in China and has a certain level of contagiousness among populations. It can also be transmitted to humans from certain animals, such as birds and pigs. In the prevention of influenza, the first step is to isolate the patient and the source of infection. The patient must not be contacted. Second, it is necessary to cut off the transmission routes, for example, industries related to the slaughter of poultry and pork should be avoided. Third, it is important to boost resistance and nutrition. Fourth, opening windows to ventilate and avoid overly polluted air can also help in preventing influenza.