Virus and Sub-Types Diagram

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.

References: 1. Short KR, Richard M, Verhagen JH, et al. One health, multiple challenges: the inter-species transmission of influenza A virus. One Health. 2015;1:1–13. 2. Taubenberger JK, Kash JC. Influenza virus evolution, host adaptation and pandemic formation. Cell Host Microbe. 2010;7(6):440–451. doi:10.1016/j.chom.2010.05.009.