Results of a Serosurvey of a Rural Population for West Nile Virus Antibodies

Cooper, Jeanie
Graham, Josh
Hutchison, Jim
Hosking, Seth
Printz, Rod
Niemeyer, Kelli
Richardson, Dallan
Gard, Philip
McFall, Jonathon
West Nile Virus (WNV) is an RNA arbovirus in the family Flaviviridae. While birds are the primary reservoir for the virus, humans can be a terminal host. In Wyoming, the Culex tarsalis mosquito acts as the primary vector. Most human infections are asymptomatic. In less than 1% of infections, however, severe symptoms including paralysis, encephalitis, and death may occur. Fremont County, population 40,123, is a hot spot for WNV in Wyoming. It is hypothesized that an inverse relationship exists between the number of reported cases and the percentage of residents previously exposed to WNV. For this serosurvey, approximately 10 milliliters of blood was drawn from 60 subjects residing in Fremont County. The blood was allowed to clot and then centrifuged to separate the serum. Serum samples were then tested for the presence of West Nile Virus IgG antibodies using Enzyme Linked Immunosorbent Assays (ELISA). The presence of high titers of IgG antibodies is indicative of past exposure to the virus. Preliminary ELISA results indicate that approximately 11% (95% CI: 5% to 22%) of the population of Fremont County has been exposed to WNV. These results indicate that a majority of the population is still at risk for WNV infection.
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