The U.S. Department of Health and Human Services reports that the flu can last one to two weeks in adults. The young, elderly and those with weakened immune systems can have the flu for longer period of time.
HHS also reports that people are contagious one day before symptoms become apparent through five to seven days after symptoms appear. The Centers for Disease Control and Prevention recommends that anyone with the flu stay at home and avoid contact with healthy individuals for at least 24 hours after any fever has disappeared. Symptoms of the flu include fever, head and body aches, fatigue, cough, sore throat, runny or stuffy nose, chills and in some cases diarrhea and vomiting.