Influenza, commonly known as the flu, is a contagious respiratory illness caused by viruses that infect the nose, throat, and lungs. It can range from mild to severe. When ill with the flu, people often feel some (or even all) of these flu symptoms:
- Fever or feeling feverish/chills (not everyone with the flu actually gets a fever)
- Cough
- Sore throat
- Runny or stuffy nose
- Muscle or body aches
- Headaches