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West Nile Virus in the United States — A Historical Perspective  [PDF]
John T. Roehrig
Viruses , 2013, DOI: 10.3390/v5123088
Abstract: Prior to 1999, West Nile virus (WNV) was a bit player in the screenplay of global vector-borne viral diseases. First discovered in the West Nile District of Uganda in 1937, this Culex sp.-transmitted virus was known for causing small human febrile outbreaks in Africa and the Middle East. Prior to 1995, the last major human WNV outbreak was in the 1950s in Israel. The epidemiology and ecology of WNV began to change in the mid-1990s when an epidemic of human encephalitis occurred in Romania. The introduction of WNV into Eastern Europe was readily explained by bird migration between Africa and Europe. The movement of WNV from Africa to Europe could not, however, predict its surprising jump across the Atlantic Ocean to New York City and the surrounding areas of the United States (U.S.). This movement of WNV from the Eastern to Western Hemisphere in 1999, and its subsequent dissemination throughout two continents in less than ten years is widely recognized as one of the most significant events in arbovirology during the last two centuries. This paper documents the early events of the introduction into and the spread of WNV in the Western Hemisphere.
A comparison of six analytical disease mapping techniques as applied to West Nile Virus in the coterminous United States
Daniel A Griffith
International Journal of Health Geographics , 2005, DOI: 10.1186/1476-072x-4-18
Abstract: West Nile Virus (WNV [1,2]), first isolated in the West Nile District of Uganda in 1937, is a flavivirus transmitted by a mosquito vector, with a general incubation period of 2–14 days following a bite by an infected mosquito, and is closely related to the St. Louis encephalitis virus that also is found in the United States (US). WNV can infect humans, birds, mosquitoes, horses and some other mammals, with mosquitoes becoming infected after feeding on the blood of birds that carry the virus (this virus enters and circulates in a mosquito's bloodstream for a few days before it settles in the insect's salivary glands); of particular concern is that the adult WNV-carrying Culex species of mosquito is able to survive through winters. WNV primarily results in bird mortality, and human and equine encephalitis. In temperate latitudes, West Nile encephalitis cases occur primarily in the late summer or early fall; WNV tends to be carried by less than 1 out of every 100 mosquitoes residing in geographic regions in which it actively circulates. WNV, with its first detected US case on Long Island in 1999, has swiftly diffused across the continental US (Figure 1a and Table 1) as well as elsewhere in the Western Hemisphere. This virus enjoyed a surprisingly rapid rate of diffusion, spreading from the New York City area to nearby localities contagiously, as well as leaping across space in a hierarchical fashion through, for example, bird migration routes (see http://westnilemaps.usgs.gov/ webcite). Although presently a person has a low risk of contracting WNV, many people infected with this virus – more than 16,000 have tested positive to date – tend to experience mild (e.g., flu-like symptoms such as fever, headache, body ache and skin rash) or no symptoms (i.e., never realizing that they have been exposed to WNV), with less than 1% of those infected developing serious illness (e.g., high fever, severe headache, stiff neck, disorientation, tremors, muscle weakness, paralysis and
A Review of Vaccine Approaches for West Nile Virus  [PDF]
Arun V. Iyer,Konstantin G. Kousoulas
International Journal of Environmental Research and Public Health , 2013, DOI: 10.3390/ijerph10094200
Abstract: The West Nile virus (WNC) first appeared in North America in 1999. The North American lineages of WNV were characterized by the presence of neuroinvasive and neurovirulent strains causing disease and death in humans, birds and horses. The 2012 WNV season in the United States saw a massive spike in the number of neuroinvasive cases and deaths similar to what was seen in the 2002–2003 season, according to the West Nile virus disease cases and deaths reported to the CDC by year and clinical presentation, 1999–2012, by ArboNET (Arboviral Diseases Branch, Centers for Disease Control and Prevention). In addition, the establishment and recent spread of lineage II WNV virus strains into Western Europe and the presence of neurovirulent and neuroinvasive strains among them is a cause of major concern. This review discusses the advances in the development of vaccines and biologicals to combat human and veterinary West Nile disease.
Spatio-temporal cluster analysis of county-based human West Nile virus incidence in the continental United States
Ramanathan Sugumaran, Scott R Larson, John P DeGroote
International Journal of Health Geographics , 2009, DOI: 10.1186/1476-072x-8-43
Abstract: The spatial scan and Local Moran's I statistics revealed several consistent, important clusters or hot-spots with significant year-to-year variation. In 2002, before the pathogen had spread throughout the country, there were significant regional clusters in the upper Midwest and in Louisiana and Mississippi. The largest and most consistent area of clustering throughout the study period was in the Northern Great Plains region including large portions of Nebraska, South Dakota, and North Dakota, and significant sections of Colorado, Wyoming, and Montana. In 2006, a very strong cluster centered in southwest Idaho was prominent. Both the spatial scan statistic and the Local Moran's I statistic were sensitive to the choice of input parameters.Significant spatial clustering of human WNV incidence has been demonstrated in the continental United States from 2002–2008. The two techniques were not always consistent in the location and size of clusters identified. Although there was significant inter-annual variation, consistent areas of clustering, with the most persistent and evident being in the Northern Great Plains, were demonstrated. Given the wide variety of mosquito species responsible and the environmental conditions they require, further spatio-temporal clustering analyses on a regional level is warranted.West Nile virus (WNV) is one of the most geographically widespread arboviruses in the world with cases occurring on all continents except Antarctica. In the United States it has resulted in nearly 29,000 human cases and over 1,100 deaths since its arrival in 1999 [1]. The Centers for Disease Control and Prevention (CDC) compile statistics on WNV incidence by county based on reporting from state health departments. In conjunction with the United States Geological Survey (USGS) and through their ArboNet system, this data is served in the form of maps and lists of counties with the number of WNV cases diagnosed [2]. Only a few studies have utilized this information on
Identification of two linear B-cell epitopes from West Nile virus NS1 by screening a phage-displayed random peptide library
En-Cheng Sun, Jian-Nan Ma, Ni-Hong Liu, Tao Yang, Jing Zhao, Hong-Wei Geng, Ling-Feng Wang, Yong-Li Qin, Zhi-Gao Bu, Yin-Hui Yang, Ross A Lunt, Lin-Fa Wang, Dong-Lai Wu
BMC Microbiology , 2011, DOI: 10.1186/1471-2180-11-160
Abstract: The present study describes the identification of two linear B-cell epitopes in WNV NS1 through screening a phage-displayed random 12-mer peptide library with two monoclonal antibodies (mAbs) 3C7 and 4D1 that directed against the NS1. The mAbs 3C7 and 4D1 recognized phages displaying peptides with the consensus motifs LTATTEK and VVDGPETKEC, respectively. Exact sequences of both motifs were found in the NS1 (895LTATTEK901 and 925VVDGPETKEC934). Further identification of the displayed B cell epitopes were conducted using a set of truncated peptides expressed as MBP fusion proteins. The data indicated that 896TATTEK901 and925VVDGPETKEC934 are minimal determinants of the linear B cell epitopes recognized by the mAbs 3C7 and 4D1, respectively. Antibodies present in the serum of WNV-positive horses recognized the minimal linear epitopes in Western blot analysis, indicating that the two peptides are antigenic in horses during infection. Furthermore, we found that the epitope recognized by 3C7 is conserved only among WNV strains, whereas the epitope recognized by 4D1 is a common motif shared among WNV and other members of Japanese encephalitis virus (JEV) serocomplex.We identified TATTEK and VVDGPETKEC as NS1-specific linear B-cell epitopes recognized by the mAbs 3C7 and 4D1, respectively. The knowledge and reagents generated in this study may have potential applications in differential diagnosis and the development of epitope-based marker vaccines against WNV and other viruses of JEV serocomplex.West Nile virus (WNV) is the etiological agent of West Nile fever (WNF), an important mosquito-borne disease widely prevalent in Africa, Europe, Russia, the Middle East, India, Australia and also in North America since 1999 [1]. WNV has expanded its geographic range since the first identification of WNV cases in the United States in 1999, and only in 2010, 981 human cases of WNF were reported in the United States [2]. WNV is serologically classified into the Japanese encephalitis
Culex quinquefasciatus (Diptera: Culicidae) as a potential West Nile virus vector in Tucson, Arizona: Blood meal analysis indicates feeding on both humans and birds
Margaret Zinser,Frank Ramberg,Elizabeth Willott
Journal of Insect Science , 2004,
Abstract: Most reports from the United States suggest Culex quinquefasciatus mosquitoes feed minimally on humans. Given the abundance of C. quinquefasciatus in residential Tucson and parts of metropolitan Phoenix, and the arrival of West Nile virus to this area, discovering the blood meal hosts of the local population is important. Using a sandwich ELISA technique, the local C. quinquefasciatus were found to feed on both humans and birds. This suggests they should be considered potential West Nile virus vectors.
Up-to-date knowledge of West Nile virus infection  [PDF]
Hrnjakovi?-Cvjetkovi? Ivana,Cvjetkovi? Dejan,Petri? Du?an,Milo?evi? Vesna
Medicinski Pregled , 2009, DOI: 10.2298/mpns0906231h
Abstract: Virus West Nile virus is a single-stranded RNA virus of the family Flaviviridae, genus Flavivirus. Epidemiology West Nile virus is maintained in the cycle involving culicine mosquitoes and birds .Humans typically acquire West Nile infection through a bite from infected adult mosquito. Person to person transmission can occur through organ transplantation, blood and blood product transfusions, transplacentally and via brest milk. Human cases of West Nile infections were recorded in Africa, Israel, Russia, India, Pakistan. In Romania in 1996 West Nile fever occurred with hundreds of neurologic cases and 17 fatalities. First human cases in the United States were in New York City where 59 persons were infected and had fever, meningitis, encephalitis and flaccid paralysis. Clinical manifestation Most human cases are asymptomatic. The majority of symptomatic patients have a self limited febrile illness. Fatigue, nausea, vomiting, eye pain, headache, myalgias, artralgias, lymphadenopathy and rash are common complaints. Less than 1% of all infected persons develop more severe neurologic illness including meningitis, encefalitis and flaccid paralysis. Laboratory diagnosis Diagnosis of West Nile virus infection is based on serologic testing, isolation of virus from patient samples and detection of viral antigen or viral genom. ELISA test and indirect immunofluorescenceassay are used for detecting IgM and IgG antibodies in serum and cerebrospinal fluid. Treatment In vitro studies have suggested that ribavirin and interferon alfa -2b may be useful in the treatment of West Nile virus disease. Prevention The most important measures are mosquito control program and personal protective measures. .
Ecological Niche of the 2003 West Nile Virus Epidemic in the Northern Great Plains of the United States  [PDF]
Michael C. Wimberly, Michael B. Hildreth, Stephen P. Boyte, Erik Lindquist, Lon Kightlinger
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0003744
Abstract: Background The incidence of West Nile virus (WNv) has remained high in the northern Great Plains compared to the rest of the United States. However, the reasons for the sustained high risk of WNv transmission in this region have not been determined. To assess the environmental drivers of WNv in the northern Great Plains, we analyzed the county-level spatial pattern of human cases during the 2003 epidemic across a seven-state region. Methodology/Principal Findings County-level data on WNv cases were examined using spatial cluster analysis, and were used to fit statistical models with weather, climate, and land use variables as predictors. In 2003 there was a single large cluster of elevated WNv risk encompassing North Dakota, South Dakota, and Nebraska along with portions of eastern Montana and Wyoming. The relative risk of WNv remained high within the boundaries of this cluster from 2004–2007. WNv incidence during the 2003 epidemic was found to have a stronger relationship with long-term climate patterns than with annual weather in either 2002 or 2003. WNv incidence increased with mean May–July temperature and had a unimodal relationship with total May–July precipitation. WNv incidence also increased with the percentage of irrigated cropland and with the percentage of the human population living in rural areas. Conclusions/Significance The spatial pattern of WNv cases during the 2003 epidemic in the northern Great Plains was associated with both climatic gradients and land use patterns. These results were interpreted as evidence that environmental conditions across much of the northern Great Plains create a favorable ecological niche for Culex tarsalis, a particularly efficient vector of WNv. Further research is needed to determine the proximal causes of sustained WNv transmission and to enhance strategies for disease prevention.
Remote Sensing of Climatic Anomalies and West Nile Virus Incidence in the Northern Great Plains of the United States  [PDF]
Ting-Wu Chuang, Michael C. Wimberly
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046882
Abstract: The northern Great Plains (NGP) of the United States has been a hotspot of West Nile virus (WNV) incidence since 2002. Mosquito ecology and the transmission of vector-borne disease are influenced by multiple environmental factors, and climatic variability is an important driver of inter-annual variation in WNV transmission risk. This study applied multiple environmental predictors including land surface temperature (LST), the normalized difference vegetation index (NDVI) and actual evapotranspiration (ETa) derived from Moderate-Resolution Imaging Spectroradiometer (MODIS) products to establish prediction models for WNV risk in the NGP. These environmental metrics are sensitive to seasonal and inter-annual fluctuations in temperature and precipitation, and are hypothesized to influence mosquito population dynamics and WNV transmission. Non-linear generalized additive models (GAMs) were used to evaluate the influences of deviations of cumulative LST, NDVI, and ETa on inter-annual variations of WNV incidence from 2004–2010. The models were sensitive to the timing of spring green up (measured with NDVI), temperature variability in early spring and summer (measured with LST), and moisture availability from late spring through early summer (measured with ETa), highlighting seasonal changes in the influences of climatic fluctuations on WNV transmission. Predictions based on these variables indicated a low WNV risk across the NGP in 2011, which is concordant with the low case reports in this year. Environmental monitoring using remote-sensed data can contribute to surveillance of WNV risk and prediction of future WNV outbreaks in space and time.
A GIS-driven integrated real-time surveillance pilot system for national West Nile virus dead bird surveillance in Canada
Jiangping Shuai, Peter Buck, Paul Sockett, Jeff Aramini, Frank Pollari
International Journal of Health Geographics , 2006, DOI: 10.1186/1476-072x-5-17
Abstract: A pilot system was developed to integrate real-time surveillance, real-time GIS, and Open GIS technology in order to enhance West Nile virus dead bird surveillance in Canada.Driven and linked by the newly developed real-time web GIS technology, this integrated real-time surveillance system includes conventional real-time web-based surveillance components, integrated real-time GIS components, and integrated Open GIS components. The pilot system identified the major GIS functions and capacities that may be important to public health surveillance. The six web GIS clients provide a wide range of GIS tools for public health surveillance. The pilot system has been serving Canadian national West Nile virus dead bird surveillance since 2005 and is adaptable to serve other disease surveillance.This pilot system has streamlined, enriched and enhanced national West Nile virus dead bird surveillance in Canada, improved productivity, and reduced operation cost. Its real-time GIS technology, static map technology, WMS integration, and its integration with non-GIS real-time surveillance system made this pilot system unique in surveillance and public health GIS.West Nile virus was first isolated in 1937 in the West Nile district of Uganda. Since then, Egypt, Israel, South Africa, and in parts of Europe, Asia and North America have reported West Nile virus infections. In North America, West Nile virus was first reported in New York City in 1999. During 2002, more than 4,000 people in North America became ill after being infected with West Nile virus. The latter was the largest outbreak of West Nile virus infection recorded. West Nile virus activities were reported in more than 40 states in the United States in 2004 [1].In August 2001, West Nile virus activity was first reported in Canada, when the virus was found in dead birds and mosquito pools in Southern Ontario. In 2002, Canada reported its' first confirmed human cases in parts of Quebec and Ontario. The virus was also found in
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