Risk Factors Associated with Human Infection during the 2006 West Nile Virus Outbreak in Davis, a Residential Community in Northern California

Abstract

We collected a total of 15,329 mosquitoes during weekly sampling in Davis, CA, from April through mid-October 2006 at 21 trap sites uniformly spaced 1.5 km apart over an area of approximately 26 km(2). Of these mosquitoes, 1,355 pools of Culex spp. were tested by multiplex reverse transcriptase-polymerase chain reaction, of which 16 pools (1.2%) were positive for West Nile virus (WNV). A degree-day model with a developmental threshold of 14.3 degrees C accurately predicted episodic WNV transmission after three extrinsic incubation periods after initial detection. Kriging interpolation delineated that Culex tarsalis were most abundant at traps near surrounding agriculture, whereas Cx. pipiens clustered within residential areas and greenbelt systems in the old portion of Davis. Spatial-temporal analyses were performed to test for clustering of locations of WNV-infected dead birds and traps with WNV-positive Cx. tarsalis and Cx. pipiens; human case incidence was mapped by census blocks. Significant multivariate spatial-temporal clustering was detected among WNV-infected dead birds and WNV-positive Cx. tarsalis, and a WNV-positive Cx. pipiens cluster overlapped areas with high incidences of confirmed human cases. Spatial analyses of WNV surveillance data may be an effective method to identify areas with an increased risk for human infection and to target control efforts to reduce the incidence of human disease.

Mosquitoes and West Nile Virus Along a River Corridor from Prairie to Montane Habitats in Eastern Colorado

“…pipiens are important local WNV vectors (Bolling et al 2007, Gujral et al 2007), which agrees with other studies in the western U.S. (e.g., Reisen et al 2004Reisen et al , 2008Reisen et al , 2009Bell et al 2005;DiMenna et al 2006DiMenna et al , 2007Nielsen et al 2008;Kent et al 2009). The study by Bolling et al (2007) also revealed that the highly abundant human-biter Aedes vexans occasionally is infected with WNV in the Front Range.…”

“…tarsalis females recorded by us for the plains in 2007 agrees with another study from Weld County in 2007 that also reported high WNV infection rates in Cx. tarsalis (Kent et al 2009 (Nielsen et al 2008). Notably, we did not record any WNV infection in Culex mosquitoes in foothills-montane areas above 1,550 m.…”

Landscape, demographic and climatic associations with human West Nile virus occurrence regionally in 2012 in the United States of America

“…Around Davis, California, warm nightly temperatures and positive WNV Cx. pipiens mosquito pools indicated high risk for human WNV incidence (Nielsen et al, 2008). In the Chicago, Illinois area cumulative high temperature differences were a key factor for distinguishing years with higher mosquito infection and higher human illness rates (Ruiz et al, 2010).…”

“…In the USA, there have been numerous national (Landesman et al, 2007;Soverow et al, 2009), state/regional (Day and Shaman, 2008;DeGroote et al, 2008;Wimeberly et al, 2008;Liu et al, 2009), and local Nielsen et al, 2008;Ghosh and Guha, 2010) studies that have investigated or discussed the relationships between WNV infections and at least one landscape, demographic or climatic-related variable. However, to date there have been a lack of studies comprehensively examining regional patterns of WNV occurrence in relation to a range of landscape, demographic and climatically related variables based on ranges of WNV mosquito vector species in the coterminous USA.…”

Efficacy of Aerial Spraying of Mosquito Adulticide in Reducing Incidence of West Nile Virus, California, 2005

“…tarsalis, respectively (8)(9)(10). To reduce WNV transmission and human exposure to mosquitoes in 2005, the Sacramento-Yolo Mosquito and Vector Control District (SYMVCD) implemented a battery of control practices from their Integrated Pest Management plan (11), an ecosystem-based strategy focused on long-term control of mosquito populations (D. Brown, SYMVCD, pers.…”