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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
The use of early summer mosquito surveillance to predict late summer West Nile virus activityGinsberg, Howard S.2010

The use of early summer mosquito surveillance to predict late summer West Nile virus activity

Keywords

Aedes;Culex;surveillance;West Nile virus, WNV

Abstract

Utility of early-season mosquito surveillance to predict West Nile virus activity in late summer was assessed in Suffolk County, NY. Dry ice-baited CDC miniature light traps paired with gravid traps were set weekly. Maximum-likelihood estimates of WNV positivity, minimum infection rates, and % positive pools were generally well correlated. However, positivity in gravid traps was not correlated with positivity in CDC light traps. The best early-season predictors of WNV activity in late summer (estimated using maximum-likelihood estimates of Culex positivity in August and September) were early date of first positive pool, low numbers of mosquitoes in July, and low numbers of mosquito species in July. These results suggest that early-season entomological samples can be used to predict WNV activity later in the summer, when most human cases are acquired. Additional research is needed to establish which surveillance variables are most predictive and to characterize the reliability of the predictions.

Authors

Ginsberg, Howard S., Rochlin, Ilia and Campbell, Scott R.

Year Published

2010

Publication

Journal of Vector Ecology

Locations
DOI

10.1111/j.1948-7134.2010.00055.x

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20618645

Bird Community Composition Linked to Human West Nile Virus Cases Along the Colorado Front RangeMcKenzie, Valerie J.2010

Bird Community Composition Linked to Human West Nile Virus Cases Along the Colorado Front Range

Keywords

WNV

Abstract

In the present study, we examined whether bird community composition can predict the annual number of human West Nile virus (WNV) cases on a per county basis in the Colorado Front Range, a region that experienced high numbers of human cases during the early part of the North American epidemic. We analyzed data sets pertaining to birds and human WNV cases from multiple existing databases between the years 2002 and 2008. Based on previous studies that used amplification fractions to compare the relative competence of different bird species, ten bird species that are common in Colorado were selected and categorized as high amplification birds, such as the American Robin (Turdus migratorius), or low amplification birds, such as the American Crow (Corvus brachyrhynchos). A general linear modeling analysis was used with an information theoretic (AIC) model sorting approach to examine which of the models best predicted the number of human WNV cases per county. Candidate models included year as a covariate and one of several bird community descriptors (e.g., richness, diversity, total bird abundance, high amplification abundance, or low amplification abundance). Results demonstrated that high amplification birds were a significant predictor of human WNV cases between 2002 and 2008. Our results suggest that a small subset of the bird community with high amplification fractions may drive the dynamics of human disease risk for West Nile. This study has implications for surveillance of West Nile and may offer insight into disease risk associated with other vector-borne zoonotic diseases.

Authors

McKenzie, Valerie J. and Goulet, Nicolas E.

Year Published

2010

Publication

EcoHealth

Locations
DOI

10.1007/s10393-010-0360-8

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21125307

Economic Conditions Predict Prevalence of West Nile VirusHarrigan, Ryan J.2010

Economic Conditions Predict Prevalence of West Nile Virus

Keywords

WNV

Abstract

Understanding the conditions underlying the proliferation of infectious diseases is crucial for mitigating future outbreaks. Since its arrival in North America in 1999, West Nile virus (WNV) has led to population-wide declines of bird species, morbidity and mortality of humans, and expenditures of millions of dollars on treatment and control. To understand the environmental conditions that best explain and predict WNV prevalence, we employed recently developed spatial modeling techniques in a recognized WNV hotspot, Orange County, California. Our models explained 85-95% of the variation of WNV prevalence in mosquito vectors, and WNV presence in secondary human hosts. Prevalence in both vectors and humans was best explained by economic variables, specifically per capita income, and by anthropogenic characteristics of the environment, particularly human population and neglected swimming pool density. While previous studies have shown associations between anthropogenic change and pathogen presence, results show that poorer economic conditions may act as a direct surrogate for environmental characteristics related to WNV prevalence. Low-income areas may be associated with higher prevalence for a number of reasons, including variations in property upkeep, microhabitat conditions conducive to viral amplification in both vectors and hosts, host community composition, and human behavioral responses related to differences in education or political participation. Results emphasize the importance and utility of including economic variables in mapping spatial risk assessments of disease.

Authors

Harrigan, Ryan J., Thomassen, Henri A., Buermann, Wolfgang, Cummings, Robert F., Kahn, Matthew E. and Smith, Thomas B.

Year Published

2010

Publication

PLOS One

Locations
DOI

10.1371/journal.pone.0015437

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21103053

Field-Based Estimates of Avian Mortality from West Nile Virus InfectionWard, Michael P.2010

Field-Based Estimates of Avian Mortality from West Nile Virus Infection

Keywords

WNV

Abstract

One of the unique characteristics of West Nile virus (WNV) in North America is the large number of bird species for which the virus can be fatal. WNV mortality has been documented through experimental infections of captive birds and necropsies of free-ranging birds. Investigations of WNV-related mortality in wild birds often focus on species with dramatic population declines (e.g., American Crow, Corvus brachyrhynchos); however, few studies have addressed WNV-related mortality in species not exhibiting marked population declines since the arrival of WNV. We conducted a mark-recapture study of 204 Northern Cardinals (Cardinalis cardinalis) in an area with endemic WNV activity to estimate WNV-related mortality. Previous research has shown that once a bird is infected and recovers from WNV it develops antibodies making it resistant to future infection. Assuming that mortality risks from non-WNV causes were the same for individuals with (had been exposed to WNV) and without antibodies (had not been exposed to WNV), we compared the survival rates of birds with and without WNV antibodies to estimate the impact of WNV on wild birds. An information theoretic approach was used, and the apparent survival was found to be 34.6% lower for individuals without antibodies during the period when WNV was most active (July-September). However, the apparent survival rate was 9.0% higher for individuals without antibodies over the rest of the year. These differences in apparent survival suggest that WNV increases mortality during the WNV season and that chronic effects of WNV infection may also be contributing to mortality. Although WNV appears to have increased mortality rates within the population, population trend data do not indicate declines, suggesting that some cardinal populations can compensate for WNV-related mortality.

Authors

Ward, Michael P., Beveroth, Tara A., Lampman, Richard, Raim, Arlo, Enstrom, David and Novak, Robert

Year Published

2010

Publication

Vector-Borne and Zoonotic Diseases

Locations
DOI

10.1089/vbz.2008.0198

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20370425

Bloodmeal Host Congregation and Landscape Structure Impact the Estimation of Female Mosquito (Diptera: Culicidae) Abundance Using Dry Ice-Baited TrapsThiemann, Tara2011

Bloodmeal Host Congregation and Landscape Structure Impact the Estimation of Female Mosquito (Diptera: Culicidae) Abundance Using Dry Ice-Baited Traps

Keywords

Culex tarsalis, Anopheles freeborni, dry ice-baited traps, abundance, California, WNV

Abstract

Vegetation patterns and the presence of large numbers of nesting herons and egrets significantly altered the number of host-seeking Culex tarsalis Coquillett (Diptera: Culicidae) collected at dry ice-baited traps. The numbers of females collected per trap night at traps along the ecotone of Eucalyptus stands with and without a heron colony were always greater or equal to numbers collected at traps within or under canopy. No Cx. tarsalis were collected within or under Eucaplytus canopy during the peak heron nesting season, even though these birds frequently were infected with West Nile virus and large number of engorged females could be collected at resting boxes. These data indicate a diversion of host-seeking females from traps to nesting birds reducing sampling efficiency.

Authors

Thiemann, Tara, Nelms, Brittany and Reisen, William K.

Year Published

2011

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME10273

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21661310

Simulation of the seasonal cycles of bird, equine and human West Nile virus casesLaperriere, Vincent2011

Simulation of the seasonal cycles of bird, equine and human West Nile virus cases

Keywords

Zoonosis; Arbovirus; Infectious disease; West Nile virus; Epidemic model; Climate forcing; Temperature dependent parameters; Seasons, WNV

Abstract

The West Nile virus (WNV) is an arthropod-borne virus (arbovirus) circulating in a natural transmission cycle between mosquitoes (enzootic vectors) and birds (amplifying hosts). Additionally, mainly horses and humans (dead-end hosts) may be infected by blood-feeding mosquitoes (bridge vectors). We developed an epidemic model for the simulation of the WNV dynamics of birds, horses and humans in the U.S., which we apply to the Minneapolis metropolitan area (Minnesota). The SEIR-type model comprises a total of 19 compartments, that are 4 compartments for mosquitoes and 5 compartments or health states for each of the 3 host species. It is the first WNV model that simulates the seasonal cycle by explicitly considering the environmental temperature. The latter determines model parameters responsible for the population dynamics of the mosquitoes and the extrinsic incubation period. Once initialized, our WNV model runs for the entire period 2002–2009, exclusively forced by environmental temperature. Simulated incidences are mainly determined by host and vector population dynamics, virus transmission and herd immunity, respectively. We adjusted our WNV model to fit monthly totals of reported bird, equine and human cases in the Minneapolis metropolitan area. From this process we estimated that the proportion of actually WNV-induced dead birds reported by the Centers for Disease Control and Prevention is about 0.8%, whereas 7.3% of equine and 10.7% of human cases were reported. This is consistent with referenced expert opinions whereby about 10% of equine and human cases are symptomatic (the other 90% of asymptomatic cases are usually not reported). Despite the restricted completeness of surveillance data and field observations, all major peaks in the observed time series were caught by the simulations. Correlation coefficients between observed and simulated time series were R = 0.75 for dead birds, R = 0.96 for symptomatic equine cases and R = 0.86 for human neuroinvasive cases, respectively.

Authors

Laperriere, Vincent, Brugger, Katharina and Rubel, Franz

Year Published

2011

Publication

Preventive Veterinary Medicine

Locations
DOI

10.1016/j.prevetmed.2010.10.013

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21093946

North American West Nile virus genotype isolates demonstrate differential replicative capacities in response to temperatureAndrade, C. C.2011

North American West Nile virus genotype isolates demonstrate differential replicative capacities in response to temperature

Keywords

WNV

Abstract

The presence of West Nile virus (WNV) was first documented in California, USA, during the summer of 2003, and subsequently the virus has become endemic throughout the state. Sequence analysis has demonstrated that the circulating strains are representative of the North American (WN02) genotype that has displaced the East Coast genotype (NY99). A recent study has indicated that enhanced vector competence at elevated temperatures may have played a role in the displacement of the East Coast genotype by WN02. In the current study, four WN02 strains from California, including an initial 2003 isolate (COAV997), were compared to strain NY99 in growth curve assays in mosquito and duck embryonic fibroblast (DEF) cell lines at differing, biologically relevant temperatures to assess the relative temperature sensitivities of these natural isolates. COAV997 was significantly debilitated in viral replication in DEF cells at 44 °C. Full-length sequence comparison of COAV997 against the NY99 reference strain revealed non-synonymous mutations in the envelope glycoprotein (V159A), non-structural protein 1 (NS1) (K110N) and non-structural protein 4A (NS4A) (F92L), as well as two mutations in the 3' UTR: C→T at nt 10 772 and A→G at nt 10 851. These non-synonymous mutations were introduced into the NY99 viral backbone by site-directed mutagenesis. A mutant containing the NS1-K110N and NS4A-F92L mutations exhibited a debilitated growth phenotype in DEF cells at 44 °C, similar to that of COAV997. One explanation for the subsistence of this genotype is that COAV997 was obtained from an area of California where avian host species might not present elevated temperatures. These data indicate that the NS1 and NS4A mutations identified in some WN02 isolates could reduce thermal stability and impede replication of virus at temperatures observed in febrile avian hosts.

Authors

Andrade, C. C., Maharaj, P. D., Reisen, W. K. and Brault, A. C.

Year Published

2011

Publication

Journal of General Virology

Locations
DOI

10.1099/vir.0.032318-0

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21775581

The Impact of Adulticide Applications on Mosquito Density in Chicago, 2005Mutebi, John-Paul2011

The Impact of Adulticide Applications on Mosquito Density in Chicago, 2005

Keywords

WNV

Abstract

The city of Chicago used ground ultra-low volume treatments of sumithrin (ANVIL 10+10) in areas with high West Nile virus infection rates among Culex mosquitoes. Two sequential treatments in Morbidity and Mortality Weekly Reports wk 31 and 32 decreased mean mosquito density by 54% from 2.5 to 1.1 mosquitoes per trap-day, whereas mosquito density increased by 153% from 1.3 to 3.3 mosquitoes per trap-day at the nonsprayed sites. The difference between these changes in mosquito density was statistically significant (confidence intervals for the difference in change: -4.7 to -1.9). Sequential adulticide treatments in September (wk 34 and 35) had no effect on mosquito density, probably because it was late in the season and the mosquitoes were presumably entering diapause and less active. Overall, there was significant decrease in mosquito density at the trap sites treated in all 4 wk (wk 31, 32, 34, and 35), suggesting that sustained sequential treatments suppressed mosquito density. Maximum likelihood estimates (MLE) of infection rate estimates varied independently of adulticide treatments, suggesting that the adulticide treatments had no direct effect on MLE. Mosquito trap counts were low, which was probably due to large numbers of alternative oviposition sites, especially catch basins competing with the gravid traps.

Authors

Mutebi, John-Paul, Delorey, Mark J., Jones, Roderick C., Plate, David K., Gerber, Susan I., Gibbs, Kevin P., Sun, Gouhe, Cohen, Nicole J. and Paul, William S.

Year Published

2011

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/10-6045.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21476450

Emergence of Culex pipiens from Overwintering HibernaculaCiota, Alexander T.2011

Emergence of Culex pipiens from Overwintering Hibernacula

Keywords

Culex pipiens, overwintering, mark–recapture, West Nile virus, WNV

Abstract

Overwintering populations of Culex pipiens, the principal enzootic vector of West Nile virus in the northeastern USA, were studied over 3 consecutive winters from 2006 to 2008, using mark–recapture techniques to determine when Cx. pipiens females began to disperse from overwintering hibernacula and how their survival influenced early season populations. In February of each year, Cx. pipiens were aspirated and marked using fluorescent powder; 4,067, 752, and 3,070 diapausing Cx. pipiens were marked in each successive year. Mosquitoes were then trapped from mid-April to early May of each year using 19 Centers for Disease Control and Prevention (CDC) light traps and 16 CDC gravid traps. A total of 348, 39, and 111 Culex mosquitoes were captured in the spring of 2006, 2007, and 2008, respectively. The number of mosquitoes marked in overwintering habitats is generally positively correlated with the number of mosquitoes recaptured in the early spring (linear regression, R2  =  0.79, P  =  0.04), yet results also suggest that seasonal variations beyond overwintering population size are likely important in determining the success of emergent populations. A single marked Cx. pipiens was captured in both 2006 and 2008. In 2006, the mosquito was captured 0.5 km from its overwintering site while in 2008 the mosquito was captured 0.3 km from its overwintering site. In all study years, mosquitoes consistently began exiting overwintering hibernacula the 3rd week of April, yet evidence of earlier exodus was observed in 2007, when outside temperatures were significantly higher in preceding days and months.

Authors

Ciota, Alexander T., Drummond, Cori L., Drobnack, Jason, Ruby, Meghan A., Kramer, Laura D. and Ebel, Gregory D.

Year Published

2011

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/8756-971X-27.1.21

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21476444

Molecular evolution of West Nile virus in a northern temperate region: Connecticut, USA 1999–2008ARMSTRONG, PHILIP M.2011

Molecular evolution of West Nile virus in a northern temperate region: Connecticut, USA 1999–2008

Keywords

Phylogeny; Flaviviridae; Flavivirus; West Nile virus; Molecular epidemiology; Viral evolution, WNV

Abstract

West Nile virus (WNV) has become firmly established in northeastern US, reemerging every summer since its introduction into North America in 1999. To determine whether WNV overwinters locally or is reseeded annually, we examined the patterns of viral lineage persistence and replacement in Connecticut over 10 consecutive transmission seasons by phylogenetic analysis. In addition, we compared the full protein coding sequence among WNV isolates to search for evidence of convergent and adaptive evolution. Viruses sampled from Connecticut segregated into a number of well-supported subclades by year of isolation with few clades persisting ≥ 2 years. Similar viral strains were dispersed in different locations across the state and divergent strains appeared within a single location during a single transmission season, implying widespread movement and rapid colonization of virus. Numerous amino acid substitutions arose in the population but only one change, V → A at position 159 of the envelope protein, became permanently fixed. Several instances of parallel evolution were identified in independent lineages, including one amino acid change in the NS4A protein that appears to be positively selected. Our results suggest that annual reemergence of WNV is driven by both reintroduction and local-overwintering of virus. Despite ongoing evolution of WNV, most amino acid variants occurred at low frequencies and were transient in the virus population.

Authors

ARMSTRONG, PHILIP M., Vossbrinck, Charles R., Andreadis, Theodore G., Anderson, John F., Pesko, Kendra N., Newman, Ruchi M., Lennon, Niall J., Birren, Bruce W., Ebel, Gregory D. and Henn, Mathew R.

Year Published

2011

Publication

Virology

Locations
DOI

10.1016/j.virol.2011.06.006

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21723580

Recent Articles

Effects of Temperature on Emergence and Seasonality of West Nile Virus in California

by Hartley, D. M., Barker, C. M., Le Menach, A., Niu, T., Gaff, H. D. and Reisen, W. K.

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...

published 2012 in American Journal of Tropical Medicine and Hygiene

Weather Variability Affects Abundance of Larval culex (diptera: Culicidae) in Storm Water Catch Basins in Suburban Chicago

by Gardner, Allison M., Hamer, Gabriel L., Hines, Alicia M., Newman, Christina M., Walker, Edward D. and Ruiz, Marilyn O.

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...

published 2012 in Journal of Medical Entomology


Wild Birds as Sentinels for Multiple Zoonotic Pathogens Along an Urban to Rural Gradient in Greater Chicago, Illinois

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

Wild birds are important in the maintenance and transmission of many zoonotic pathogens. With increasing urbanization and the resulting emergence of zoonotic diseases, it is critical to understand the relationships among birds, vectors, zoonotic pathogens, and the urban landscape. Here, we use wild birds as sentinels across a gradient of urbanization to understand the relative risk of diseases ...

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