Abstract
West Nile virus (WNV) has become the most epidemiologically important mosquito-borne disease in the United States, causing ~50,000 cases since its introduction in 1999. Transmitted primarily by Culex species, WNV transmission requires the complex interplay between bird reservoirs and mosquito vectors, with human cases the result of epizootic spillover. To better understand the intrinsic factors that drive these interactions, we have compiled infection data from sentinel chickens, mosquito vectors, and human cases in Iowa over a 15 year period (2002–2016) to better understand the spatial and temporal components that drive WNV transmission. Supplementing these findings with mosquito abundance, distribution, and host preferences data, we provide strong support that Culex tarsalis is the most important vector of human WNV infections in the region. Together, our analysis provides new insights into WNV infection patterns in multiple hosts and highlights the importance of long-term surveillance to understand the dynamics of mosquito-borne-disease transmission.
Highlights
In an era of increased concern over mosquito-borne viruses, West Nile virus (WNV) continues to have the largest epidemiological impact in the United States, causing ~50,000 cases and over 2,100 deaths since its introduction in 19991
Factors influencing WNV transmission have been broadly described across the United States[8,25,26,27], yet our understanding of WNV transmission in the Midwest has heavily relied on studies of the Chicago metropolitan area[10,12,28,29,30,31,32] with only limited characterization of WNV epidemiology and transmission dynamics in other locations of the Midwest[14,15,33,34,35]
We provide a comprehensive view of 15 years of WNV transmission in Iowa (2002 to 2016) following its introduction into the state
Summary
In an era of increased concern over mosquito-borne viruses, West Nile virus (WNV) continues to have the largest epidemiological impact in the United States, causing ~50,000 cases and over 2,100 deaths since its introduction in 19991. Previous reports describing patterns of WNV transmission in densely populated urban/suburban areas[9,10,11,12] and rural environments[13,14], suggest that distinct mechanisms of peridomestic and sylvatic transmission may influence the epidemiology of WNV across the US8 This is supported by considerations of land use and landscape ecology, which serve as important determinants in shaping the geographical distributions of mosquito vectors[15,16,17,18,19]. By examining host infection rates from spatial and temporal perspectives, we have determined when and where WNV is most actively being transmitted in Iowa, which suggests underlying biotic and abiotic mechanisms that likely influence WNV transmission Together, these data provide strong support that Cx. tarsalis is the predominant vector of human WNV transmission in Iowa. These analyses provide new insights into WNV transmission dynamics in the Upper Midwest region and highlight the importance of long-term surveillance to understand mosquito borne-disease
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