Influenza (also known as flu) is a contagious respiratory illness caused by flu viruses. It can cause mild to severe illness, and at times can lead to death. Flu is different from a cold. Flu usually comes on suddenly. People who are sick with flu often feel some or all of these symptoms:
- Fever* or feeling feverish/chills
- Sore throat
- Runny or stuffy nose
- Muscle or body aches
- Fatigue (tiredness)
- Some people may have vomiting and diarrhea, though this is more common in children than adults.
*It’s important to note that not everyone with flu will have a fever.