Influenza, or the 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.
Two strains of flu, seasonal flu and the H1N1 (Swine) flu, are currently circulating in the United States. A third, highly lethal H5N1 (Bird) flu is being closely tracked overseas.
Most healthy people recover from the flu without problems, but certain people are at high risk for serious complications.
Extensive efforts are underway to track and monitor the spread of all flu viruses. In the U.S., epidemiologists at the Centers for Disease Control (CDC) are working with states to collect, compile and analyze reports of flu outbreaks. More on the current situation from the CDC.
Flu symptoms may include fever, coughing, sore throat, runny or stuffy nose, headaches, body aches, chills and fatigue. In H1N1 (Swine) flu infection, vomiting and diarrhea may also occur.
Annual outbreaks of the seasonal flu usually occur during the late fall through early spring. Most people have natural immunity, and a seasonal flu vaccine is available. In a typical year, approximately 5 to 20 percent of the population gets the seasonal flu and approximately 36,000 flu-related deaths are reported.