The genetic material of influenza A virus (IAV) is made up of 8 segments of RNA containing 8–11 genes, which code for different attributes of the virus (e.g., attachment, replication).1 The H (hemagglutinins or HA) and N (neuraminidase or NA) components of the IAV are the key genes responsible for attachment and release of the virus from respiratory cells, respectively.1,2
Different sub-types of IAV are named according to differences in the HA and NA components, which can evolve over time due to genetic shift and drift.1,2 The most common sub-types of IAV affecting swine globally are H1N1, H1N2, and H3N2.1,2 There is little cross reactivity between the subtypes, which helps to explain why pigs are often “re-infected” with different influenza A viruses throughout their life.
