An active surveillance of influenza viruses in swine is necessary for two basic reasons; to track the influenza virus evolution for improvements of the currently available diagnostic tests as well as for generating more effective vaccines for prevention and control of disease [49]. The currently available scientific data on swine influenza viruses would serve as a key to understand their evolutionary dynamics and transmission patterns. Therefore, this systematic review, for the first time, summarizes all four types of influenza viruses in the swine populations worldwide.