Flu Season Calendar

When (and what) exactly defines the “flu season” calendar?During flu season, people are at the highest risk of developing the influenza virus.

In the United States, the flu season is considered October through May.

During the 35-year period between 1976 and 2011, flu activity most often peaked in February. Other high-ranking months for flu activity include: January, March and December. To stay protected through flu season, you should get vaccinated as soon as the vaccine is available.

What is flu season, and why does it change from year to year?

In the U.S., flu season generally peaks in the winter, but the timing and duration of flu symptoms vary based on where influenza activity is occurring and the strain of influenza that is circulating.

What resources can I use to track flu season?

You can track the flu virus on the website for the Center for Disease Control and Prevention. The CDC collects, compiles and analyzes information on influenza activity year round in the United States and produces a weekly report from October through mid-May.

You can track the influenza virus and the current flu season online here:

When is the best time for a flu shot? Before or during flu season?

The best time for a flu shot is before flu season. According to the CDC, everyone 6 months of age and older should get their annual flu vaccine as soon as it is available. Vaccination before December is best since this timing ensures that protective antibodies are in place before flu activity is typically at its highest.


Centers for Disease Control and Prevention. Seasonal Flu (Influenza): The Flu Season. Retrieved from: January 29, 2012.

Smith, Nicole M. Prevention and Control of Influenza, Recommendations of the ACIP: Sources of Information Regarding Influenza and Its Surveillance. Retrieved from: January 29, 2012.

Centers for Disease Control and Prevention. Seasonal Influenza (Flu): When should I get a flu vaccination? Retrieved from: January 29, 2012.