Mapping Changes in West Nile Virus Activity from 2012 to 2025 using Mosquito Surveillance Data

Abstract

West Nile virus (WNV) is the leading mosquito-borne disease in the U.S., infecting birds, mosquitoes, and humans. Because mosquito activity varies across regions, seasons and over time, spatial surveillance is needed to identify areas at high risk. Although mosquito surveillance programs collect WNV data, changes in positive pool distribution over time are not always clearly visualized, leading to inaccurate conclusions. Prince William County has ongoing surveillance of WNV in mosquitoes. Each year mosquito samples collected weekly from at least 50 sites are tested for WNV. This study compares the spatial distribution of the samples to detect changes in virus positivity. Weekly surveillance records (epiyear, epiweek, trapsite, etc.) were merged with a master coordinate list in GoogleSheets by sorting sites alphabetically per year and copying coordinates across active sites. Next, in GoogleMyMaps, these sheets were used to generate four annual maps showing trap locations, combined positive/negative sites, positive-only sites, and negative-only sites. Compared to 2012, more locations in 2025 had positive mosquitoes. Positivity peaked cyclically every few years between 2012-2019, then increased steadily from 2019 to 2025. Sites with positive pools during multiple years over the 14 year surveillance include Woodbridge, Neabsco, Manassas/Manassas Park, and I-95. These maps show how spatiotemporal analysis helps track WNV changes and identify high-risk areas. Using effective digital mapping to track mosquito activity, officials can target their vector-control efforts and their public health interventions. Future research will examine the effects of weather on mosquito behavior and virus transmission.