Influenza is caused by a virus that spreads from one infected person to another.
Influenza can cause:
fever · sore throat · chills· cough · headache · muscle aches
Anyone can get influenza. Most people are ill with influenza for only a few days, but some get much sicker and may need to be hospitalized.
Influenza causes an average of 36,000 deaths each year in the U.S., mostly among the elderly.