Influenza is a contagious, upper-respiratory disease caused by many different strains of influenza viruses. While many people use the imprecise term “flu” to describe 24- or 48-hour bouts of illness, real influenza can interfere with normal daily activities for as long as a week.
Influenza is not a minor inconvenience. As many as 200,000 Americans are hospitalized because of it each year, and as many as 36,000 die of the disease or complications associated with it.
Children under age 1, people 65 or older, and people suffering from underlying medical conditions are at a higher risk of serious complications.