How Long Does The Flu Last 2024 In Us. Symptoms are worst for the first three days. More evidence points to long flu being a real phenomenon, with a large study showing symptoms persist at least 4 weeks or more after some people are.

Research suggests that maximum immunity is achieved shortly after getting a flu vaccine and decreases with each passing month. Flu season in the united states typically stretches from october to february, though activity can last as late as may, according to the cdc.