The flu, or influenza, typically lasts for about one to two weeks. However, the duration can vary depending on the individual and their overall health. The onset of symptoms is usually sudden and can include fever, chills, cough, sore throat, runny or stuffy nose, body aches, headache, fatigue, and weakness. The flu is most contagious during the first three to four days of symptoms, and people are typically contagious for up to a week. However, some people may be contagious for longer, particularly if they are still experiencing symptoms or if they have a weakened immune system.