Different types of influenza (flu viruses) can infect the nose, throat, and lungs. Flu viruses spread in communities each fall and winter. This period is known as flu season. Flu illness can be mild, but it can also be severe and lead to hospitalization or death.

In the United States, influenza types A and B cause seasonal flu each year.

The best way to prevent the flu is to receive a flu vaccine every year. The vaccine can prevent infection or reduce the severity of illness if you do get sick.