Influenza refers to a disease characterized primarily by coughing, sputum production, sore throat, and fever, after the respiratory tract has been infected by the influenza virus. Additionally, influenza may present symptoms such as nausea, abdominal pain, and diarrhea. The infectiousness of influenza is mainly transmitted through the inhalation of droplets from one person to another within a population. In China, influenza is a legally mandated Class B infectious disease, and is indeed contagious. Therefore, if you notice individuals around you with fever, cough, or sputum production who are suspected of having influenza, isolation should be implemented. Moreover, it is advisable to avoid crowded places to reduce the possibility of being infected by influenza. Furthermore, vaccination during the flu season is also an effective way to protect against influenza.