Master of Public Health, The Ohio State University, 2018, Public Health

Influenza A virus is a zoonotic pathogen whose introduction to humans from animals could potentially cause a pandemic. Animal-linage influenza A viruses (IAVs) that infect humans are referred to as variant IAVs, which are designated with a `v' after the subtype. To better understand the epidemiology of IAV in exhibition swine and resulting H3N2v in humans, we performed a phylogenetic analysis using full genome sequences from 279 IAV isolates collected from exhibition swine in 5 states from 2013-2015 and 23 of the 25 H3N2v cases reported during those same years. Sixty-six fairs (23.7%) had at least one sample that was positive for IAV and 20 of those fairs (30.3%) had more than one IAV genotype circulating in the pigs. An overall 3-year prevalence of 9.7% (95% CI: 9.1-10.3) was observed. However, the prevalence of IAV in swine significantly decreased from 2014 to 2015 when the proportion of fairs with IAV infected pigs decreased from 30.14% (95% CI: 19.6-40.1) in 2014 to 13.5% (95% CI: 6.9-20.1) in 2015. We found 19 IAV genotypes infecting swine and 6 IAV genotypes in humans, with 5 genotypes in both host species. There was a positive correlation between the number of fairs at which a genotype was present among the pigs and the number of human cases of that same genotype. Additionally, we showed that H3N2v isolates clustered tightly with exhibition swine isolates that were prevalent in the same year. Our data indicate that there are multiple genotypes of swine-lineage IAV that can infect humans, and highly prevalent IAV genotypes during a given year are the strains most likely to infect humans.

Committee: Andrew Bowman DVM, MS, PhD (Advisor); Armando Hoet DVM, PhD (Committee Member); Gregory Habing DVM, PhD (Committee Member); Kurt Stevenson MD, MPH (Committee Member) Subjects: Animal Diseases; Animals; Public Health