Flu, or influenza, is a contagious respiratory disease that infects 10 to 20 percent ofĀ U.S. residents. The U.S. Centers for Disease Control and Prevention estimates that an annual average of 114,000Ā Americans are hospitalized due to flu complications, with 36,000 deaths. The 2003-2004 āflu seasonā beganĀ earlier than expected, with a sudden surge in cases in November 2003; severity was also greater than normal.
