Most influenza is not contagious after 1 to 7 days of illness and is not contagious to others. However, seriously ill patients may still be contagious for more than 7 days. Influenza is an acute respiratory infectious disease caused by influenza virus, through droplets, contact and other infectious, mostly in the fall and winter, common symptoms include high fever, fatigue, general body aches and pains, respiratory symptoms are mild, but usually in 3 to 14 days can be self-cured, or life-threatening in severe cases. Influenza virus mutates easily and is highly contagious, patients are contagious for 1 to 7 days after the onset of the disease, and the disease is most contagious for the first 2 to 3 days, most of them will not be infectious to others after 1 to 7 days, but those who are seriously ill may be contagious for more than 7 days. Annual influenza vaccination can effectively prevent influenza, and at the same time need to maintain good personal hygiene habits, try to avoid contact with influenza patients. Seek medical attention if you experience any of the above symptoms.