The annual number of influenza-associated deaths from respiratory and circulatory cases varies widely from year-to-year, ranging from an estimated 3,349 to 48,614.
Centers for Disease Control and Prevention. Estimates of Deaths Associated with Seasonal Influenza: United States, 1976-2007. Morbidity and Mortality Weekly Report. August 27, 2010; 59(33): 1057-62. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5933a1.htm