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. More on the current situation. Flu symptoms may include fever, coughing, sore throat, runny or stuffy nose, headaches, body aches, chills and fatigue.