Having had the flu for a short period of time can lead to getting it again, such as re-infecting yourself with other subtypes of the flu virus. Influenza refers to the common cold and is caused by infection of the body with the influenza virus. There are many subtypes of influenza viruses, and influenza viruses are highly mutable, so new strains of influenza viruses can appear within a short period of time. After you have had the flu and have recovered from it, your body produces antibodies to the influenza virus, which correspond to the subtype of influenza virus you have been infected with, so it is unlikely that you will be infected with that subtype of influenza virus in a short period of time. If you are exposed to another subtype of influenza virus within a short period of time after recovery, you may be re-infected due to the lack of antibodies to that subtype of virus. It is recommended to take personal precautions during the influenza epidemic season.