Compared with most other viral respiratory infections, such as the common cold, influenza infection often causes a more severe illness. Most people who get the flu recover completely in one to two weeks, but some people develop serious and potentially life-threatening medical complications, such as pneumonia. Between 25-50 million people in the United States are infected each year with the influenza virus. In an average year, infection with influenza virus is associated with 20,000 deaths nationwide and more than 100,000 hospitalizations. Approximately 90 million workdays are lost and 30 million school days are missed each year as a result of influenza.
Vaccination can prevent disease caused by influenza.
Unlike vaccines used against other viruses such as measles, mumps, rubella and varicella, people need to be vaccinated annually against influenza. This is because the influenza virus often changes its genetic composition to evade the immune system of its host. Thus, people are susceptible to influenza virus infection throughout life. The Centers for Disease Control and Prevention recommends a flu shot for healthy adults over age 50 and high-risk children and adults. Unfortunately, less than one percent of healthy children and less than 30 percent of healthy adults, are routinely vaccinated.