A Systematic Review analyzing the Comparative Ecology and Evolution of Swine Influenza Viruses in China and the United States

Keywords: influenza, medical & health geography, swine flu
Abstract Type: Poster Abstract

Abstract

Influenza-A viruses (IAVs) are responsible for substantial human and animal morbidity and mortality. Pigs, in particular, can act as intermediate host “mixing vessels” that generate pandemic IAV strains through genetic reassortment among avian, swine, and/or human IAVs. Since 2009, novel swine IAVs (SIVs) arising from reassortment between the 2009 pandemic H1N1 virus and enzootic SIVs have frequently been detected in swine populations worldwide, most noticeably in China and the US. Importantly, a number of these novel SIVs have caused spillovers to humans and raised concerns about a future influenza pandemic. Although evolutionary events (i.e., reassortment and mutations) have been readily documented, it is not clear which evolutionary events pose threats to human and animal health, and which ecological principles are driving such events. In this study, we review the role of ecological drivers on pandemic swine influenza evolution in China and the US, the two largest pork producing countries accounting for 60% of the global swine population. By using a comparative approach, we describe the unique swine system ecologies among the two countries and their contributions to SIV evolution including intercontinental movement of genetic segments. For example, China has a higher proportion of backyard hog production and lower rates of vaccination compared to the US, while the US has a high feral hog population that may further enhance SIV evolution at the wildlife-domestic animal interface. Finally, we highlight critical gaps in our understanding of IAV evolution at the human-swine interface and the need for further comparative studies.