The flu and the common cold are caused by different viruses. So a cold can’t really “morph” into the flu. If you or your child develops the flu, it was caused by a flu virus in the first place. Because the two types of illnesses have similar symptoms, it can be challenging to tell the difference between them based on how you feel. Colds generally don’t result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations.