Date of Award

2026

Document Type

Embargoed Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Dr. Catherine Miller

Second Advisor

Dr. Rachel Larsen

Third Advisor

Dr. Doug Currie

Abstract

West Nile virus (WNV) is the leading cause of mosquito-borne illness in the United States and remains a persistent public health concern. Although most infections are asymptomatic, the virus poses a significant threat to the elderly and immunocompromised populations, who are at the greatest risk for developing severe complications. Symptoms of WNV ranging from flu-like complications to neuroinvasive disease. Neuroinvasive West Nile is a severe form of WNV, which can cause swelling of the brain, a life-threatening condition that requires immediate hospitalization and poses lifelong complications. Despite evidence of widespread circulation of WNV since its introduction to the United States in 1999, population-level exposure remains poorly characterized, and no seroprevalence studies have previously been conducted in Maine. Maine is significant not only because of the current lack of data on WNV exposure in the population, but also because of the heightened risk that WNV poses to Maine's population. Maine has the oldest population in the country, putting its population at the greatest risk for severe or neuroinvasive disease. This study aimed to establish the first-ever baseline for the seroprevalence of WNV exposure among immunocompetent adults currently residing in Southern Maine. Blood samples were collected from 112 adult volunteers using a minimally invasive finger-stick method. Serum was isolated and screened for WNV-specific IgG antibodies using an optimized pseudovirionbased enzyme-linked immunosorbent assay (ELISA). A subset of samples was further tested using a confirmatory WNV whole-virus lysate ELISA to assess assay concordance and specificity. Among 83 subjects tested under finalized screening conditions, 19 exceeded the predetermined positivity threshold, corresponding to a seroprevalence of 22.9% (95% CI: 14.8– 34.2%). Confirmatory testing using WNV lysate demonstrated overall concordance with the screening assay while revealing a small number of discordant cases, consistent with differences in antigen presentation and assay sensitivity. These findings support that WNV exposure among adults in Southern Maine is substantially higher than previously hypothesized based on known, regional data. This study provides the first serological evidence of WNV exposure in Maine and establishes a foundation for expanded surveillance efforts, risk assessment, and public health planning related to mosquito-borne disease transmission in the region.

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Available for download on Saturday, August 11, 2029

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