The influenza virus is contagious for roughly 5 to 7 days after symptoms begin for most adults, with the contagious window starting about 1 day before symptoms appear and continuing through about 5 to 7 days after illness onset. Children, older adults, and people with weakened immune systems may shed the virus for longer, sometimes up to 7–10 days or more in some cases. The period of peak contagiousness is typically during the first 3 days of symptoms, when viral shedding and coughing are greatest. If you have flu symptoms, it’s wise to stay home and avoid close contact with others, especially high-risk individuals, until you’ve been fever-free for at least 24 hours without antipyretic medications and symptoms have started to improve.