Find A Physician More on Flu (Influenza) More on Flu (Influenza)
Research and Clinical Trials More on Flu (Influenza) What is
influenza (flu)? Influenza (or flu) is a highly contagious viral
respiratory tract infection. An estimated 5 to 20 percent of the
population in the US contract influenza each year. Influenza is
characterized by the abrupt onset of fever, muscle aches, sore
throat, and a nonproductive cough. Influenza can make people of
any age ill. Although most people are ill with influenza for
only a few days, some have a much more serious illness and may
need to be hospitalized. Influenza can also lead to pneumonia
and death. Influenza viruses are divided into three types,
designated as A, B, and C. - Influenza types A and B are
responsible for epidemics of respiratory illness that occur
almost every winter and are often associated with increased
rates for hospitalization and death. Efforts to control the
impact of influenza are focused on types A and B. - Influenza
type C usually causes either a ve