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United States Articles found through PubMed 2000-2012

Description

West Nile Virus (WNV) is a mosquito-borne virus that can infect humans. Originally known in East Africa, WNV has now spread throughout the world. The first case of WNV in the western hemisphere was identified in New York in 1999, and within 5 years the disease had spread throughout the United States and into Canada, Latin America, and the Caribbean. While most of WNV infections cause no symptoms, the remaining cases show flu-like symptoms, and can lead to neurological disease or death.

latest article added on November 2013

ArticleFirst AuthorPublished
Persistent West Nile Virus Transmission and the Apparent Displacement St. Louis Encephalitis Virus in Southeastern California, 2003–2006Reisen, William K.2008

Persistent West Nile Virus Transmission and the Apparent Displacement St. Louis Encephalitis Virus in Southeastern California, 2003–2006

Keywords

West Nile virus, St. Louis encephalitis virus, western equine encephalomyelitis virus, Culex tarsalis, Culex pipiens quinquefasciatus, WNV

Abstract

West Nile virus (family Flaviviridae, genus Flavivirus, WNV) invaded the Colorado Desert biome of southern California during summer 2003 and seemed to displace previously endemic St. Louis encephalitis virus (family Flaviviridae, genus Flavivirus, SLEV, an antigenically similar Flavivirus in the Japanese encephalitis virus serocomplex). Western equine encephalomyelitis virus (family Togaviridae, genus Alphavirus, WEEV), an antigenically distinct Alphavirus, was detected during 2005 and 2006, indicating that conditions were suitable for encephalitis virus introduction and detection. Cross-protective “avian herd immunity” due to WNV infection possibly may have prevented SLEV reintroduction and/or amplification to detectable levels. During 2003–2006, WNV was consistently active at wetlands and agricultural habitats surrounding the Salton Sea where Culex tarsalis Coquillett served as the primary enzootic maintenance and amplification vector. Based on published laboratory infection studies and the current seroprevalence estimates, house sparrows, house finches, and several Ardeidae may have been important avian amplifying hosts in this region. Transmission efficiency may have been dampened by high infection rates in incompetent avian hosts, including Gamble’s quail, mourning doves, common ground doves, and domestic pigeons. Early season WNV amplification and dispersal from North Shore in the southeastern portion of the Coachella Valley resulted in sporadic WNV incursions into the urbanized Upper Valley near Palm Springs, where Culex pipiens quinquefasciatus Say was the primary enzootic and bridge vector. Although relatively few human cases were detected during the 2003–2006 period, all were concentrated in the Upper Valley and were associated with high human population density and WNV infection in peridomestic populations of Cx. p. quinquefasciatus. Intensive early mosquito control during 2006 seemed to interrupt and delay transmission, perhaps setting the stage for the future reintroduction of SLEV.

Authors

Reisen, William K., Fang, Ying, Lothrop, Hugh D., Wheeler, Sarah S., Kennsington, Marc, Gutierrez, Arturo, Garcia, Sandra and Lothrop, Branka

Year Published

2008

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2008)45[494:PWNVTA]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18533445

Locating suitable habitats for West Nile Virus-infected mosquitoes through association of environmental characteristics with infected mosquito locations: a case study in Shelby County, TennesseeOzdenerol, Esra2008

Locating suitable habitats for West Nile Virus-infected mosquitoes through association of environmental characteristics with infected mosquito locations: a case study in Shelby County, Tennessee

Keywords

WNV

Abstract

Background Since its first detection in 2001, West Nile Virus (WNV) poses a significant health risk for residents of Shelby County in Tennessee. This situation forced public health officials to adopt efficient methods for monitoring disease spread and predicting future outbreaks. Analyses that use environmental variables to find suitable habitats for WNV-infected mosquitoes have the potential to support these efforts. Using the Mahalanobis Distance statistic, we identified areas of Shelby County that are ecologically most suitable for sustaining WNV, based on similarity of environmental characteristics to areas where WNV was found. The environmental characteristics in this study were based on Geographic Information Systems (GIS) data, such as elevation, slope, land use, vegetation density, temperature, and precipitation. Results Our analyses produced maps of likely habitats of WNV-infected mosquitoes for each week of August 2004, revealing the areas that are ecologically most suitable for sustaining WNV within the core of the Memphis urban area. By comparing neighbourhood social characteristics to the environmental factors that contribute to WNV infection, potential social drivers of WNV transmission were revealed in Shelby County. Results show that human population characteristics and housing conditions such as a high percentage of black population, low income, high rental occupation, old structures, and vacant housing are associated with the focal area of WNV identified for each week of the study period. Conclusion We demonstrated that use of the Mahalanobis Distance statistic as a similarity index to assess environmental characteristics is a potential raster-based approach to identify areas ecologically most suitable for sustaining the virus. This approach was also useful to monitor changes over time for likely locations of infected mosquito habitats. This technique is very helpful for authorities when making decisions related to an integrated mosquito management plan and targeted health education outreach.

Authors

Ozdenerol, Esra, Bialkowska-Jelinska, Elzbieta and Taff, Gregory N

Year Published

2008

Publication

International Journal of Health Geographics

Locations
DOI

10.1186/1476-072X-7-12

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18373868

Comparative Analysis of Distribution and Abundance of West Nile and Eastern Equine Encephalomyelitis Virus Vectors in Suffolk County, New York, Using Human Population Density and Land Use/Cover DataRochlin, I.2008

Comparative Analysis of Distribution and Abundance of West Nile and Eastern Equine Encephalomyelitis Virus Vectors in Suffolk County, New York, Using Human Population Density and Land Use/Cover Data

Keywords

mosquito vectors, urban, rural, GIS, West Nile virus, WNV

Abstract

Five years of CDC light trap data from Suffolk County, NY, were analyzed to compare the applicability of human population density (HPD) and land use/cover (LUC) classification systems to describe mosquito abundance and to determine whether certain mosquito species of medical importance tend to be more common in urban (defined by HPD) or residential (defined by LUC) areas. Eleven study sites were categorized as urban or rural using U.S. Census Bureau data and by LUC types using geographic information systems (GISs). Abundance and percent composition of nine mosquito taxa, all known or potential vectors of arboviruses, were analyzed to determine spatial patterns. By HPD definitions, three mosquito species, Aedes canadensis (Theobald), Coquillettidia perturbans (Walker), and Culiseta melanura (Coquillett), differed significantly between habitat types, with higher abundance and percent composition in rural areas. Abundance and percent composition of these three species also increased with freshwater wetland, natural vegetation areas, or a combination when using LUC definitions. Additionally, two species, Ae. canadensis and Cs. melanura, were negatively affected by increased residential area. One species, Aedes vexans (Meigen), had higher percent composition in urban areas. Two medically important taxa, Culex spp. and Aedes triseriatus (Say), were proportionally more prevalent in residential areas by LUC classification, as was Aedes trivittatus (Coquillett). Although HPD classification was readily available and had some predictive value, LUC classification resulted in higher spatial resolution and better ability to develop location specific predictive models.

Authors

Rochlin, I., Harding, K., Ginsberg, H. S. and Campbell, S. R.

Year Published

2008

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2008)45[563:CAODAA]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18533453

Identification of hyperendemic foci of horses with West Nile virus disease in TexasWittich, Courtney A.2008

Identification of hyperendemic foci of horses with West Nile virus disease in Texas

Keywords

WNV

Abstract

Objective—To determine whether West Nile virus (WNV) disease hyperendemic foci (hot spots) exist within the horse population in Texas and, if detected, to identify the locations. Sample Population—Reports of 1,907 horses with WNV disease in Texas from 2002 to 2004. Procedures—Case data with spatial information from WNV epidemics occurring in 2002 (1,377 horses), 2003 (396 horses), and 2004 (134 horses) were analyzed by use of the spatial scan statistic (Poisson model) and kriging of empirical Bayes smoothed county attack rates to determine locations of horses with WNV disease in which affected horses were consistently (in each of the 3 study years) clustered (hyperendemic foci, or hot spots). Results—2 WNV hot spots in Texas, an area in northwestern Texas and an area in eastern Texas, were identified with the scan statistic. Risk maps of the WNV epidemics were qualitatively consistent with the hot spots identified. Conclusions and Clinical Relevance—WNV hot spots existed within the horse population in Texas (2002 to 2004). Knowledge of disease hot spots allows disease control and prevention programs to be made more efficient through targeted surveillance and education.

Authors

Ward, Michael P., Wittich, Courtney A., Fosgate, Geoffrey T. and Srinivasan, Raghavan

Year Published

2008

Publication

American Journal of Veterinary Research

Locations
DOI

10.2460/ajvr.69.3.378

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18312137

Salt Marsh as Culex salinarius Larval Habitat in Coastal New YorkRochlin, Ilia2008

Salt Marsh as Culex salinarius Larval Habitat in Coastal New York

Keywords

WNV

Abstract

Culex salinarius is considered one of the most likely bridge vectors involved in the human transmission cycle of West Nile virus (WNV) and eastern equine encephalomyelitis virus (EEEV) in the northeastern USA. The larval habitats of this species in the coastal region of New York State are currently poorly known. Between 2005 and 2007, a larval survey was carried out to identify and characterize possible larval habitats in Suffolk County, encompassing natural and man-made freshwater wetlands, artificial containers, and salt marshes. Only relatively undisturbed salt marsh yielded Cx. salinarius larvae in considerable numbers from several sites over a period of 2 years. The immature stages of this species were found associated with Spartina patens and S. alterniflora of the upper marsh at salinities ranging from 4.3 to 18.8 parts per thousand. Both heavily impacted and relatively undisturbed salt marshes produced several hundreds of adult Cx. salinarius per Centers for Disease Control and Prevention (CDC) light trap per night, an order of magnitude higher than CDC light traps deployed at upland sites. The ability of Cx. salinarius to use both heavily impacted and relatively undisturbed salt marshes for reproduction has significant repercussions for marsh restoration and vector control practices.

Authors

Rochlin, Ilia, Dempsey, Mary E., Campbell, Scott R. and Ninivaggi, Dominick V.

Year Published

2008

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/5748.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18939687

Ecologic Factors Associated with West Nile Virus Transmission, Northeastern United StatesBrown, Heidi E.2008

Ecologic Factors Associated with West Nile Virus Transmission, Northeastern United States

Keywords

WNV

Abstract

Since 1999, West Nile virus (WNV) disease has affected the northeastern United States. To describe the spatial epidemiology and identify risk factors for disease incidence, we analyzed 8 years (1999-2006) of county-based human WNV disease surveillance data. Among the 56.6 million residents in 8 northeastern states sharing primary enzootic vectors, we found 977 cases. We controlled for population density and potential bias from surveillance and spatial proximity. Analyses demonstrated significant spatial spreading from 1999 through 2004 (p0.75 cases/100,000 residents) than counties with the most (>70%) forest cover. These results quantify urbanization as a risk factor for WNV disease incidence and are consistent with knowledge of vector species in this area.

Authors

Brown, Heidi E., Childs, James E., Diuk-Wasser, Maria A. and Fish, Durland

Year Published

2008

Publication

Emerging Infectious Diseases

Locations
DOI

10.3201/eid1410.071396

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18826816

Host-Seeking Heights, Host-Seeking Activity Patterns, and West Nile Virus Infection Rates for Members of the Culex pipiens Complex at Different Habitat Types Within the Hybrid Zone, Shelby County, TN, 2002 (Diptera: Culicidae)Savage, Harry M.2008

Host-Seeking Heights, Host-Seeking Activity Patterns, and West Nile Virus Infection Rates for Members of the Culex pipiens Complex at Different Habitat Types Within the Hybrid Zone, Shelby County, TN, 2002 (Diptera: Culicidae)

Keywords

Culex pipiens complex, host-seeking activity period, host-seeking height, West Nile virus, pipiens, WNV

Abstract

Host-seeking heights, host-seeking activity patterns, and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) infection rates were assessed for members of the Culex pipiens complex from July to December 2002, by using chicken-baited can traps (CT) at four ecologically different sites in Shelby County, TN. Host-seeking height was assessed by CT placed at elevations of 3.1, 4.6, and 7.6 m during one 24-h period per month. Host-seeking activity was assessed by paired CT placed at an elevation of 4.6 m. Can traps were sampled at one 10-h daytime interval and at seven 2-h intervals during the evening, night, and morning. Cx. pipiens complex mosquitoes accounted for 87.1% of collected mosquitoes. Culex (Melanoconion) erraticus (Dyar & Knab) accounted for 11.9% of specimens. The average number of Cx. pipiens complex mosquitoes collected per 24-h CT period from July to September was lowest at a rural middle income site (1.7), intermediate at an urban middle income site (11.3), and highest at an urban low income site (47.4). Can traps at the forested site failed to collect Cx. pipiens complex mosquitoes. From July to September at urban sites, Culex pipiens pipiens L. was the rarest of the three complex members accounting for 11.1–25.6% of specimens. At the rural site, Culex pipiens quinquefasciatus Say was the rarest member of the complex. Cx. p. pipiens was not collected after September. Mean abundance of Cx. pipiens complex mosquitoes was higher in traps at 7.6 m than in traps at 4.6 m. Abundances at 3.1 m were intermediate and not significantly different from abundances at the other heights. Initiation of host-seeking activity was associated with the end of civil twilight and activity occurred over an extended nighttime period lasting 8–10 h. All 11 WNV-positive mosquitoes were Cx. pipiens complex mosquitoes collected from urban sites in traps placed at elevations of 4.6 and 7.6 m. Infection rates were marginally nonsignificant by height. Infection rates, host-seeking heights, and activity patterns were not significantly different among members of the Cx. pipiens complex.

Authors

Savage, Harry M., Anderson, Michael, Gordon, Emily, McMillen, Larry, Colton, Leah, Delorey, Mark, Sutherland, Genevieve, Aspen, Stephen, Charnetzky, Dawn, Burkhalter, Kristen and Godsey, Marvin

Year Published

2008

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2008)45[276:HHHAPA]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18402144

West Nile Virus Antibodies in Permanent Resident and Overwintering Migrant Birds in South-Central KansasShelite, Thomas R.2008

West Nile Virus Antibodies in Permanent Resident and Overwintering Migrant Birds in South-Central Kansas

Keywords

WNV

Abstract

We conducted serological studies, using epitope-blocking ELISAs directed at West Nile virus (WNV) and flavivirus antibodies, of wild birds in south-central Kansas, the first for this state, in the winters of 2003-04 through 2005-06. Overwintering migratory species (primarily the American tree sparrow and dark-eyed junco) consistently showed significantly lower seropositivity than permanent residents (primarily the northern cardinal). The cardinal showed annual variation in seropositivity between winters. Of 35 birds that were serial sampled within a single winter, one cardinal may have seroconverted between late December and mid-February, providing a preliminary suggestion of continued enzootic transmission, chronic infection, or bird-bird transfer as overwintering mechanisms. Breeding population size of the cardinal did not change after the introduction of WNV to Kansas. Of eighteen birds that were serial sampled between winters, none seroconverted. Among overwintering migrants, the Harris' Sparrow showed the highest seropositivity, possibly related to its migration route through the central Great Plains, an area of recent high WNV activity. The finding that permanent resident birds exhibit higher seropositivity than migrant birds suggests that resident birds contribute to the initiation of annual infection cycles,although this conclusion is speculative in the absence of data on viral titers and the length of viremia. KeyWords: West Nile Virus-flavivirus-birds-epitope-blocking ELISA-winter.

Authors

Shelite, Thomas R., Rogers, Christopher M., Litzner, Brandon R., Johnson, R. Roy and Schneegurt, Mark A.

Year Published

2008

Publication

Vector-Borne and Zoonotic Diseases

Locations
DOI

10.1089/vbz.2007.0176

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18471059

Evaluation of Manhole Inserts as Structural Barriers to Mosquito Entry into Belowground Stormwater Systems Using a Simulated Treatment DeviceHarbison, Justin E.2009

Evaluation of Manhole Inserts as Structural Barriers to Mosquito Entry into Belowground Stormwater Systems Using a Simulated Treatment Device

Keywords

WNV

Abstract

Belowground proprietary stormwater treatment devices can produce mosquitoes, including vectors of West Nile virus. Elimination of vertical entry points such as pick holes in manhole covers may reduce the number of mosquitoes entering and reproducing in these structures. Plastic manhole dish inserts were evaluated as structural barriers against mosquito entry through pick holes in a simulated stormwater treatment device. Inserts were 100% effective at preventing mosquito entry through covers when no other openings existed. In devices configured with an open lateral conveyance pipe, the addition of an insert under the cover reduced mosquito oviposition significantly. Subsequent trials to further elucidate mosquito entry through manhole covers found a significant positive correlation between increasing number of pick holes and mosquito oviposition. Results of the study suggest the potential for manhole dish inserts to decrease the number of mosquitoes entering belowground structures. The different available stormwater treatment systems and site-specific installations may, however, provide a much greater variety of possible alternate entry points for mosquitoes than was addressed in the current study. Further work is needed in field installations to quantify the significance of pick holes to mosquito entry and determine under what conditions, if any, manhole dish inserts would be most effective and appropriate.

Authors

Harbison, Justin E., Metzger, Marco E., Allen, Vaikko and Hu, Renjie

Year Published

2009

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/09-5897.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/19852227

Risk factors for human infection with West Nile Virus in Connecticut: a multi-year analysisLiu, Ann2009

Risk factors for human infection with West Nile Virus in Connecticut: a multi-year analysis

Keywords

WNV

Abstract

Background: The optimal method for early prediction of human West Nile virus (WNV) infection risk remains controversial. We analyzed the predictive utility of risk factor data for human WNV over a six-year period in Connecticut. Results and Discussion: Using only environmental variables or animal sentinel data was less predictive than a model that considered all variables. In the final parsimonious model, population density, growing degree-days, temperature, WNV positive mosquitoes, dead birds and WNV positive birds were significant predictors of human infection risk, with an ROC value of 0.75. Conclusion: A real-time model using climate, land use, and animal surveillance data to predict WNV risk appears feasible. The dynamic patterns of WNV infection suggest a need to periodically refine such prediction systems. Methods: Using multiple logistic regression, the 30-day risk of human WNV infection by town was modeled using environmental variables as well as mosquito and wild bird surveillance.

Authors

Liu, Ann, Lee, Vivian, Galusha, Deron, Slade, Martin D, Diuk-Wasser, Maria, Andreadis, Theodore, Scotch, Matthew and Rabinowitz, Peter M

Year Published

2009

Publication

International Journal of Health Geographics

Locations
DOI

10.1186/1476-072X-8-67

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/19943935

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Temperature has played a critical role in the spatiotemporal dynamics of West Nile virus transmission throughout California from its introduction in 2003 through establishment by 2009. We compared two novel mechanistic measures of transmission risk, the temperature-dependent ratio of virus extrinsic incubation period to the mosquito gonotrophic period (BT), and the fundamental reproductive rati...

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Culex pipiens L. (Diptera: Culicidae) and Culex restuans Theobald are the primary enzootic and bridge vectors of West Nile virus in the eastern United States north of 36° latitude. Recent studies of the natural history of these species have implicated catch basins and underground storm drain systems as important larval development sites in urban and suburban locales. Although the presence of la...

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by Hamer, S. A., Lehrer, E. and Magle, S. B.

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published 2012 in Zoonoses and Public Health

Completeness of West Nile Virus Testing in Patients with Meningitis and Encephalitis During an Outbreak in Arizona, Usa

by WEBER, I. B., LINDSEY, N. P., BUNKO-PATTERSON, A. M., BRIGGS, G., WADLEIGH, T. J., SYLVESTER, T. L., LEVY, C., KOMATSU, K. K., LEHMAN, J. A., FISCHER, M. and STAPLES, J. E.

Accurate data on West Nile virus (WNV) cases help guide public health education and control activities, and impact regional WNV blood product screening procedures. During an outbreak of WNV disease in Arizona, records from patients with meningitis or encephalitis were reviewed to determine the proportion tested for WNV. Of 60 patients identified with meningitis or encephalitis, 24 (40%) were te...

published 2012 in Epidemiology and Infection