Influenza is a viral respiratory infection characterized by fever, cough, headache, fatigue and inflammed respiratory membranes.
Influenza is much more serious than the common cold.
Cold and flu symptoms resemble each other, but differ in intensity. A cold rarely moves in to the lungs - the flu can cause pneumonia. You may be able to drag yourself to class with a cold, but with the flu, you'll be too ill to leave your bed. The most telling symptoms are fatigue and muscle aches which are normally absent with a cold. There is no cure for the flu.