What is the difference between the flu and a common cold?

The difference between a flu and a cold can be difficult to determine, because they do have very similar symptoms. They're both a virus. The cold generally comes on a little bit more slowly. It's not quite as serious, runny nose, cough, a little fatigue, whereas the flu virus comes on much more quickly. You can also have fevers, more productive cough, more general body aches, fatigue, that kind of thing. Both can come with a lot of symptoms, but the flu virus can be far more problematic for people, cause other more serious health conditions. That's the fever and more severe symptoms.