According to the Centers for Disease Control, the flu usually comes on suddenly. People who have the flu often feel some or all of these symptoms:

FLU VS. COMMON COLD

Flu Symptoms (more intense than common cold):
- Fever
- Body aches
- Extreme tiredness
- Dry cough are more common and intense
- Chills
- HeadachesCommon

Cold Symptoms: 
- Stuffy/runny nose
- Cough
- Sore throat
- Fever is rare
- Slight body aches
- Mild fatigue

 Source: Centers for Disease Control