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.
Flu symptoms may include fever, coughing, sore throat, runny or stuffy nose, headaches, body aches, chills and fatigue. In H1N1 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.