Influenza, also called the flu, is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. There are two main types of influenza viruses: Types A and B, which cause seasonal flu epidemics each year. Influenza can cause mild to severe illness, and sometimes can be fatal.
The flu often causes these symptoms:
- Fever or feeling feverish/chills
- Sore throat
- Runny or stuffy nose
- Muscle or body aches