Influenza (the flu) is an infection of the nose, throat, and lungs caused by influenza viruses.
There are many different influenza viruses that are constantly changing. They cause illness, hospital stays and deaths in the United States each year.
Older people, young children, and people with certain health conditions, are at high risk for serious flu complications. Each year about 20,000 children younger than 5 years old are hospitalized from flu complications like pneumonia.
Here are some flu basics and steps you can take if you or someone in your family does get sick.