Global Transmission of Influenza Viruses from Humans to Swine

July 25, 2012 — 

To determine the extent to which influenza viruses jump between humans and swine hosts, we undertook a large-scale phylogenetic analysis of pandemic A/H1N1/09 (H1N1pdm09) influenza virus genome sequence data. From this we identified at least 49 human-to-swine transmission events that occurred globally during 2009-2011, thereby highlighting the ability of the H1N1pdm09 virus to repeatedly transmit from humans to swine, even following adaptive evolution in humans. Similarly, we identified at least 23 separate introductions of human seasonal (non-pandemic) H1 and H3 influenza viruses into swine globally since 1990. Overall, these results reveal the frequency with which swine are exposed to human influenza viruses, indicate that humans make a substantial contribution to the genetic diversity of influenza viruses in swine, and emphasize the need to improve biosecurity measures at the human-swine interface, including influenza vaccination of swine workers.

Martha I. Nelson, Marie R. Gramer, Amy L. Vincent, & Edward C. Holmes; Global Transmission of Influenza Viruses from Humans to Swine; JGV Papers in Press. Published July 18, 2012 as doi:10.1099/vir.0.044974-0