You are typically contagious with the flu from about 1 day before symptoms appear to about 5 to 7 days after becoming sick. Some people, especially young children and those with weakened immune systems, may be contagious for a longer period. The virus spreads mainly through respiratory droplets when you cough, sneeze, or talk, so it's important to stay home when you're sick, cover your mouth when coughing, and practice good hand hygiene to prevent spreading the infection.