What's a seasonal flu ? Seasonal flu (also known as influenza) is a highly infectious [inˈfekʃəs](传染的) illness caused by a flu virus [ˈvaiərəs](病毒). The virus infects [inˈfekts](感染) your lungs and upper airways(上呼吸道), causing a sudden high temperature and general aches and pains(周身疼痛). You could also lose your appetite [ˈæpitait](食欲), feel nauseous [ˈnɔ:ʃəs, -zi:əs](想呕吐的) and have a dry cough. You may need to stay in bed until your symptoms get better. The influenza vaccine [vækˈsi:nˈvækˌsi:n](疫苗) is the best way to prevent [priˈvent](预防) the flu, and flu prevention should be a goal for everyone. When should I get a flu shot?
Because flu season may begin as early as October and run through May, the best time to get a flu shot is in October or November. You can still get an influenza vaccine in December or later, but earlier may be more beneficial [ˌbeniˈfiʃəl](有利的) in preventing flu.