Influenza A viruses (IAVs) of subtypes H1N1, H1N2 and H3N2 are endemic in swine populations worldwide. There is bidirectional IAV transmission between humans and swine and the 2009 pandemic influenza virus was of swine origin. The swine IAVs are different from human IAVs of the same subtypes and can be distinguished from them antigenically. This is due to a separate and different virus evolution in swine, and a tremendous and continuing genetic and antigenic diversity. Though swine influenza is among the 10 priority zoonotic diseases according to EFSA, surveillance remains weak. We will perform influenza surveillance in swine in Flanders, and characterize the isolated viruses genetically and antigenically. This way, we will identify the predominant swine IAVs and novel subtypes, lineages, clades and genotypes. We will compare these viruses with those circulating in swine in other parts of the world and with contemporary human IAVs. In addition, we will study the implications of swine IAV evolution for swine and human health. First, we will identify candidate swine influenza vaccine strains using a surveillance-based approach. We intend to identify objective criteria for the selection of vaccine strains that adequately capture viral diversity. Second, we will examine whether some of the novel swine IAV strains may be better fit to replicate in humans. For this purpose, we will use air-liquid interface cultures of nasal and bronchial epithelia from human donors.