Contact Us
- 800–CDC–INFO
- (800-232-4636)
- 888–232–6348 (TTY)
- cdcinfo@cdc.gov
The Flu Season
In the Northern hemisphere, winter is the time for flu. The timing and duration of flu seasons vary. While flu outbreaks can happen as early as October, most of the time influenza activity peaks in January or later. During the past 26 flu seasons, months with the heaviest flu activity (peak months) occurred in November one season, December four seasons, January five seasons, February 12 seasons, and March four seasons.
 |
Monitoring Flu Activity
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. The U.S. influenza surveillance system is a collaborative effort between CDC and its many partners in state and local health departments, public health and clinical laboratories, vital statistics offices, physicians, clinics and emergency departments, and the Departments of Defense and Veteran’s Affairs. Information in five categories is collected from 10 different data sources that allow CDC to:
- Find out when and where influenza activity is occurring
- Track influenza-related illness
- Determine what influenza viruses are circulating
- Detect changes in influenza viruses
- Measure the impact influenza is having on deaths in the United States
For more information about flu surveillance or to access these reports, visit Flu Activity & Surveillance.
- Page last modified July 16, 2008
- Content Source: Coordinating Center for Infectious Diseases (CCID)
- National Center for Immunization and Respiratory Diseases (NCIRD)
