The flu can be spread by individual who have virus but haven't developed symptoms yet. The big difference in symptoms for the flu and the "common" cold is running a higher fever. Colds tend to have fevers that are less than 100.4F while the flu generally goes higher. Colds usually start with a sore throat and then develop nasal symptoms. Individuals with the flu tend to have moderate to severe fatigue. Since there can be overlap of symptoms between the illnesses and can vary from person to person, it can be confusing. The most common difference is usually that higher temperature in the flu.