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Abstract
Transmission and maintenance of influenza A viruses (IAVs) between and across species are dependent on viruses remaining infectious while associated with both host and environmental components of the maintenance cycle. Transmission and maintenance of IAVs in wild aquatic avian reservoirs, primarily associated with the orders Anseriformes (ducks, geese) and Charadriiformes (gulls, shorebirds), are also dependent on short and long-distance bird movements which serve to link susceptible hosts. The first research objective addressed the potential role of environment in cross species transmission, specifically by characterizing the effects of temperature, pH, and salinity on the persistence and infectivity of swine and pandemic human IAVs in a distilled water model. The viruses did not differ significantly in their responses to these variables, indicating no apparent environmental adaptation as related to the movement of IAV into different host systems. The second and third objectives were aimed at understanding environmental persistence, transmission, and maintenance of IAV in a unique natural system: shorebirds at Delaware Bay. The stabilities of two of 19 IAV isolated from environmental sources and one Ruddy Turnstone (Arenaria interpres) at Delaware Bay were assessed under temperature, pH, salinity, and substrate conditions comparable to those found in the local microenvironment. All viruses remained infectious in a sand milieu for seven days, indicating that the beach environment can support short-term maintenance of IAV. Finally, the genomes of IAV isolated from shorebirds at overwintering sites in the southeastern United States were compared to those isolated from shorebirds at Delaware Bay several weeks to months later. A high degree of genetic similarity was detected for all eight gene segments, though the transfer of a homologous genome from winter to spring sites was not identified. This indicates that migrating Ruddy Turnstones are one source for introducing IAV into the Delaware Bay ecosystem. Once introduced, these viruses reassort with and are assimilated into the larger IAV gene pool at this unique site. Results of these projects allowed for the deconstruction of the factors responsible for persistence and movement of virus, and the subsequent reconstruction of the dynamics of these mechanisms at an ecological hotspot for IAV Delaware Bay.