Here's some information that might answer that common question
and hopefully, clear the confusion!
How to diagnose Influenza
(Flu)
If you have a fever (usually 39-41 deg C) and 2-3 of the symptoms
listed below, you have the flu!
Common Symptoms : Fever, Headache, Sore Throat, Dry Cough,
Lethargy, Myalgia (Muscle Pain)
Less Common Symptoms : Sneezing, Painful and Watery Eyes, Blocked /
Runny Nose
Flu vs the Common
Cold
Flu
Onset of symptoms : Sudden
Fever : High, 38-41 deg C
Muscle Aches : Severe
Malaise or Fatigue : Severe
Sore throat and cough : Early onset
Chest symptoms : Substernal burning common
Sneezing : Occasional
Duration : 7-10 days
Common Cold
Onset of Symptoms : Gradual
Fever : None or mild (less than 38 deg C)
Muscle Aches : Usually mild
Malaise / Fatigue : Usually Mild
Sore Throat and Cough : Mild course, peaking on Day 2-3
Chest Symptoms : Mild, if any
Sneezing : Common
Duration : 3-4 Days
Hope this information helps! 
