Flu refers to illnesses caused by a number of different influenza viruses. Flu can cause a range of symptoms and effects, from mild to lethal. Most healthy people recover from the flu without problems, but certain people are at high risk for serious complications. In the U.S., epidemiologists at the Centers for Disease Control (CDC) work with states to collect, compile and analyze reports of flu outbreaks. Flu symptoms may include fever, coughing, sore throat, runny or stuffy nose, headaches, body aches, chills and fatigue.
In the United States, the flu season is usually from fall through early spring. The peak of flu season has occurred anywhere from late November through March. The overall health impact (e.g., infections, hospitalizations, and deaths) of a flu season varies from year to year. On average, each year in the United States:
- 5 to 20 percent of the population get the flu
- More than 200,000 people are hospitalized from flu-related complications
- Deaths from flu-related causes range from 3,300 to 48,600 (average 23,600)