Despite evidence of West Nile virus (WNV) activity in Colombia, Venezuela and Argentina, this virus has not been reported in most South American countries. In February 2009, we commenced an investigation for WNV in mosquitoes, horses and caimans from the Pantanal, Central-West Brazil. The sera of 168 horses and 30 caimans were initially tested using a flaviviruses-specific epitope-blocking enzyme-linked immunosorbent assay (blocking ELISA) for the detection of flavivirus-reactive antibodies. The seropositive samples were further tested using a plaque-reduction neutralisation test (PRNT90) for WNV and its most closely-related flaviviruses that circulate in Brazil to confirm the detection of specific virus-neutralising antibodies. Of the 93 (55.4%) blocking ELISA-seropositive horse serum samples, five (3%) were seropositive for WNV, nine (5.4%) were seropositive for St. Louis encephalitis virus, 18 (10.7%) were seropositive for Ilheus virus, three (1.8%) were seropositive for Cacipacore virus and none were seropositive for Rocio virus using PRNT90, with a criteria of > four-fold antibody titre difference. All caimans were negative for flaviviruses-specific antibodies using the blocking ELISA. No virus genome was detected from caiman blood or mosquito samples. The present study is the first report of confirmed serological evidence of WNV activity in Brazil.

O vírus do Oeste do Nilo (VON) é um Flavivírus capaz de infectar muitas espécies de vertebrados, incluindo o homem. Embora reconhecida desde 1940, esta virose nunca havia sido descrita nas Américas, onde emergiu nos Estados Unidos ao final da década de 1990, com numerosos casos de meningoencefalite em humanos. Posteriormente, sua transmissão por transfusão de sangue e órgãos foi comprovada, levando à implantação de testes moleculares (NAT) para a triagem de doadores nos EUA e Canadá a partir de 2003. Nos anos seguintes, o VON foi sendo progressivamente detectado em países como México, Panamá e áreas do Caribe, sugerindo sua iminente introdução na América do Sul. De fato, evidências sorológicas foram reveladas em cavalos e aves na Colômbia, Venezuela, Argentina e muito recentemente no pantanal mato-grossense (em cavalos). A vigilância epidemiológica para este agente é de grande importância para a saúde pública, visto o potencial de morbimortalidade deste vírus para humanos. Sendo assim este trabalho tem o objetivo de investigar a presença do RNA do VON em amostras de doadores de sangue, pacientes com meningoencefalite ou febre de origem indeterminada e soros e amostras cerebrais de equinos. Foram analisadas 2.202 doações de sangue do Amazonas (HEMOAM)...

Processo FAPESP: 08/50167-6; Since the emergence of West Nile virus (WNV) in North America in 1999, there have been several reports of WNV activity in Central and South American countries. To detect WNV in Brazil, we performed a serological survey of horses from different regions of Brazil using recombinant peptides from domain III of WNV. Positive samples were validated with the neutralisation test. Our results showed that of 79 ELISA-positive horses, nine expressed WNV-specific neutralising antibodies. Eight of the infected horses were from the state of Mato Grosso do Sul and one was from the state of Paraiba. Our results provide additional evidence for the emergence of WNV in Brazil and for its circulation in multiple regions of the country.

The circulation of West Nile virus in Portugal was assessed by serological surveys conducted during 2004–2010 in horses and birds. The detection of WNV antibodies in both species in all the years covered by the study as well as the presence of anti-WNV IgM in symptomatic horses that had not traveled outside the country, support the notion that WNV circulates in Portugal.

Meningitis and encephalitis are complications of West Nile virus (WNV) infection. Although WNV is endemic in North America, the virus has recently been reported in Colombia and Argentina. Investigation of WNV in Brazil is important since this virus has never been studied previously in this country. OBJECTIVE: To investigate the presence of WNV infection in viral encephalitis/meningitis cases of unknown etiology in the city of Rio de Janeiro, Brazil. METHOD: Thirty-seven adults with viral meningitis/encephalitis had their serum and CSF tested for WNV antibodies using the ELISA method. RESULTS: Only one case was WNV-positive, but this case was also positive for dengue. The plaque reduction neutralization test distinguished infections, and was negative for WNV. CONCLUSION: WNV can be confused with dengue infection. Their symptoms and neurological picture are similar. We did not find WNV in any patients with encephalitis and meningitis in the city of Rio de Janeiro. Up to now, it has not been detected in Brazil

Despite evidence of West Nile virus (WNV) activity in Colombia, Venezuela and Argentina, this virus has not been reported in most South American countries. In February 2009, we commenced an investigation for WNV in mosquitoes, horses and caimans from the Pantanal, Central-West Brazil. The sera of 168 horses and 30 caimans were initially tested using a flaviviruses-specific epitope-blocking enzyme-linked immunosorbent assay (blocking ELISA) for the detection of flavivirus-reactive antibodies. The seropositive samples were further tested using a plaque-reduction neutralisation test (PRNT90) for WNV and its most closely-related flaviviruses that circulate in Brazil to confirm the detection of specific virus-neutralising antibodies. Of the 93 (55.4%) blocking ELISA-seropositive horse serum samples, five (3%) were seropositive for WNV, nine (5.4%) were seropositive for St. Louis encephalitis virus, 18 (10.7%) were seropositive for Ilheus virus, three (1.8%) were seropositive for Cacipacore virus and none were seropositive for Rocio virus using PRNT90, with a criteria of > four-fold antibody titre difference. All caimans were negative for flaviviruses-specific antibodies using the blocking ELISA. No virus genome was detected from caiman blood or mosquito samples. The present study is the first report of confirmed serological evidence of WNV activity in Brazil.

Since the emergence of West Nile virus (WNV) in North America in 1999, there have been several reports of WNV activity in Central and South American countries. To detect WNV in Brazil, we performed a serological survey of horses from different regions of Brazil using recombinant peptides from domain III of WNV. Positive samples were validated with the neutralisation test. Our results showed that of 79 ELISA-positive horses, nine expressed WNV-specific neutralising antibodies. Eight of the infected horses were from the state of Mato Grosso do Sul and one was from the state of Paraíba. Our results provide additional evidence for the emergence of WNV in Brazil and for its circulation in multiple regions of the country.

West Nile virus (WNV) envelope glycoproteins preM/E were stably expressed in baby hamster kidney cells and tested as antigen in a fluorescent antibody assay for WNV antibodies. Sera from horses, mice and chicken immunized with an inactivated WNV vaccine and, less consistently, sera from horses acutely infected with WNV, reacted specifically with viral antigens present in preM/E-expressing cells.

West Nile virus is transmitted by urban-dwelling mosquitoes to birds and other animals, with occasional “spillover” to humans. While the means by which West Nile virus was introduced into the Americas in 1999 remain unknown, the climatic conditions that amplify diseases that cycle among urban mosquitoes, birds, and humans are warm winters and spring droughts. This information can be useful in generating early warning systems and mobilizing timely and the most environmentally friendly public health interventions. The extreme weather conditions accompanying long-term climate change may also be contributing to the spread of West Nile virus in the United States and Europe.

The intentional or unintentional introduction of a pathogen in an urban setting presents severe communication chanllenges. Risk communication—a science-based approach for communicating effectively in high-concern situations—provides a set of principles and tools for meeting those challenges. A brief overview of the risk communication theoretical perspective and basic risk communication models is presented here, and the risk communication perspective is applied to the West Nile virus epidemic in New York City in 1999 and 2000 and to a possible bioterrorist event. The purpose is to provide practical information on how perceptions of the risks associated with a disease outbreak might be perceived and how communications would be best managed.

Background: The effects of weather on West Nile virus (WNV) mosquito populations in the United States have been widely reported, but few studies assess their overall impact on transmission to humans. Objectives: We investigated meteorologic conditions associated with reported human WNV cases in the United States. Methods: We conducted a case–crossover study to assess 16,298 human WNV cases reported to the Centers for Disease Control and Prevention from 2001 to 2005. The primary outcome measures were the incidence rate ratio of disease occurrence associated with mean weekly maximum temperature, cumulative weekly temperature, mean weekly dew point temperature, cumulative weekly precipitation, and the presence of ≥ 1 day of heavy rainfall (≥ 50 mm) during the month prior to symptom onset. Results: Increasing weekly maximum temperature and weekly cumulative temperature were similarly and significantly associated with a 35–83% higher incidence of reported WNV infection over the next month. An increase in mean weekly dew point temperature was significantly associated with a 9–38% higher incidence over the subsequent 3 weeks. The presence of at least 1 day of heavy rainfall within a week was associated with a 29–66% higher incidence during the same week and over the subsequent 2 weeks. A 20-mm increase in cumulative weekly precipitation was significantly associated with a 4–8% increase in incidence of reported WNV infection over the subsequent 2 weeks. Conclusions: Warmer temperatures...

Pyrethroid pesticides were applied via ground spraying to residential neighborhoods in New York City during July–September 2000 to control mosquito vectors of West Nile virus (WNV). Case reports link pyrethroid exposure to asthma exacerbations, but population-level effects on asthma from large-scale mosquito control programs have not been assessed. We conducted this analysis to determine whether widespread urban pyrethroid pesticide use was associated with increased rates of emergency department (ED) visits for asthma. We recorded the dates and locations of pyrethroid spraying during the 2000 WNV season in New York City and tabulated all ED visits for asthma to public hospitals from October 1999 through November 2000 by date and ZIP code of patients’ residences. The association between pesticide application and asthma-related emergency visits was evaluated across date and ZIP code, adjusting for season, day of week, and daily temperature, precipitation, particulate, and ozone levels. There were 62,827 ED visits for asthma during the 14-month study period, across 162 ZIP codes. The number of asthma visits was similar in the 3-day periods before and after spraying (510 vs. 501, p = 0.78). In multivariate analyses, daily rates of asthma visits were not associated with pesticide spraying (rate ratio = 0.92; 95% confidence interval...

The goal ofthis literature review is to inform the reader on several aspects of West Nile Virus (WNV) transmission by its mosquito vector, Culex pipiens and to elucidate how Cx. pipiens and WNV are intertwined. The first few sections of the literature review describe the life cycle and blood feeding behaviours ofmosquitoes so that baseline data ofmosquito biology are established. In addition to explaining how and why a mosquito blood feeds, the section on "Blood Meal Analysis" describes the different methods for determining the vertebrate source of mosquito blood meals and a brief history of these testing methods. Since this thesis looks at the feeding behaviour of Cx. pipiens, it is important to know how to determine what they are feeding upon. Discussion on other mosquito-borne diseases related to WNV gives a broader perspective to the thesis, and examines other diseases that have occurred in Ontario in the past. This is followed by background information on WNV and theories on how this virus came to North America and how it relates to Cx. pipiens. The final sections discuss Cx. pipiens and give background information to how this species of mosquito exists and behaves within North America.

West Nile virus (WNV) is a zoonotic arthropod-borne pathogen with continued geographical expansion in Europe. We present and evaluate data on the temporal, spatial and bird species focus of the WNV surveillance programme in dead wild birds in Great Britain (2002–2009). During this period all bird samples tested negative for WNV. Eighty-two per cent of the 2072 submissions occurred during the peak period of vector activity with 53% tested during April–July before human and equine infection would be expected. Samples were received from every county, but there was significant geographical clustering (nearest neighbour index=0·23, P<0·001). Over 240 species were represented, with surveillance more likely to detect WNV in resident bird species (92% of submissions) than migrants (8%). Evidence indicates that widespread avian mortality is not generally a reported feature of WNV in Europe and hence additional activities other than dead bird surveillance may maximize the ability to detect WNV circulation before the onset of human and equine infections.; V.A. Brugman, D.L. Horton, L.P. Phipps, N. Johnson, A.J.C. Cook, A.R. Fooks and A.C. Breed

Background. West Nile Virus (WNV), a mosquito-borne flavivirus, is one of an increasing number of infectious diseases that have been emerging or re-emerging in the last two decades. Since the arrival ofWNV to Canada to present date, the Niagara Region has only reported 30 clinical cases, a small number compared to the hundreds reported in other regions of similar conditions. Moreover, the last reported human case in Niagara was in 2006. As it has been demonstrated that the majority of WNV infections are asymptomatic, the question remains whether the lack of clinical cases in Niagara truly reflects the lack of transmission to humans or if infections are still occurring but are mostly asymptomatic. Objectives. The general objective of this study was to establish whether or not active WNV transmission could be detected in a human population residing in Niagara for the 2007 transmission season. To fullfil this objective, a cross-sectional seroprevalence study was designed to investigate for the presence of anti-WNV antibodies in a sample of Mexican migrant agricultural workers employed in farms registered with the Seasonal Agricultural Workers Program (SAWP). Due to the Mexican origin of the study participants, three specific research objectives were proposed: a) determine the seroprevalence ofanti-WNV antibodies as well as anti-Dengue virus antibodies (a closely related virus prevalent in Mexico and likely to confound WNV serology); b) analyze risk factors associated with WNV and Dengue virus seropositivity; and c) assess the awareness of study participants about WNV infection as well as their understanding of the mode of transmission and clinical importance of the infection. Methodology: After obtaining ethics clearance from Brock University...

The West Nile virus outbreak in 1999 demonstrated the country's capacity to meet an emerging public health threat. However, while the tracking and monitoring efforts that were put into place by 2000 were impressive, the response to the West Nile virus underscores a fundamental deficiency in the capacity of public health regarding the nation's environmental health efforts. Chronic diseases such as asthma, neurological diseases, and birth defects and their potential links to environmental factors are not being adequately tracked and monitored. New public health infrastructure resources are required.

El virus West Nile es un flavivirus patógeno para humanos en el Viejo Mundo que ha experimentado recientemente un proceso de emergencia en el continente americano. Desde su introducción en 1999 en EEUU, se ha convertido en un patógeno de preocupación para las poblaciones de aves silvestres al haber provocado allí eventos masivos de mortalidad y porque numerosas especies de aves han experimentado disminuciones significativas de sus poblaciones. Para 2001 el virus ya se había dispersado fuera de EEUU, extendiéndose por América del Sur, América Central y el Caribe. Debido a la falta de un sistema de vigilancia activo para esta patología, no se conoce su verdadero impacto sobre las poblaciones silvestres en esas regiones. Sin embargo, la ausencia de epizootias indica una marcada diferencia en el comportamiento epidemiológico del virus con respecto a EEUU. En Argentina, su ecoepidemiología está poco estudiada y ha recibido poca atención en el ámbito ornitológico. Existen antecedentes de aislamiento viral en equinos enfermos y muertos, casos febriles y de encefalitis en humanos y detección de anticuerpos en aves silvestres en provincias del centro y norte del país. En este trabajo se brinda un análisis actualizado de la situación ecoepidemiológica del virus West Nile...

El virus West Nile es un flavivirus patógeno para humanos en el Viejo Mundo que ha experimentado recientemente un proceso de emergencia en el continente americano. Desde su introducción en 1999 en EEUU, se ha convertido en un patógeno de preocupación para las poblaciones de aves silvestres al haber provocado allí eventos masivos de mortalidad y porque numerosas especies de aves han experimentado disminuciones significativas de sus poblaciones. Para 2001 el virus ya se había dispersado fuera de EEUU, extendiéndose por América del Sur, América Central y el Caribe. Debido a la falta de un sistema de vigilancia activo para esta patología, no se conoce su verdadero impacto sobre las poblaciones silvestres en esas regiones. Sin embargo, la ausencia de epizootias indica una marcada diferencia en el comportamiento epidemiológico del virus con respecto a EEUU. En Argentina, su ecoepidemiología está poco estudiada y ha recibido poca atención en el ámbito ornitológico. Existen antecedentes de aislamiento viral en equinos enfermos y muertos, casos febriles y de encefalitis en humanos y detección de anticuerpos en aves silvestres en provincias del centro y norte del país. En este trabajo se brinda un análisis actualizado de la situación ecoepidemiológica del virus West Nile...

BACKGROUND The two-component NS2B-NS3 proteases of West Nile and dengue viruses are essential for viral replication and established targets for drug development. In all crystal structures of the proteases to date, the NS2B cofactor is located far from the substrate binding site (open conformation) in the absence of inhibitor and lining the substrate binding site (closed conformation) in the presence of an inhibitor. METHODS In this work, nuclear magnetic resonance (NMR) spectroscopy of isotope and spin-labeled samples of the West Nile virus protease was used to investigate the occurrence of equilibria between open and closed conformations in solution. FINDINGS In solution, the closed form of the West Nile virus protease is the predominant conformation irrespective of the presence or absence of inhibitors. Nonetheless, dissociation of the C-terminal part of the NS2B cofactor from the NS3 protease (open conformation) occurs in both the presence and the absence of inhibitors. Low-molecular-weight inhibitors can shift the conformational exchange equilibria so that over 90% of the West Nile virus protease molecules assume the closed conformation. The West Nile virus protease differs from the dengue virus protease, where the open conformation is the predominant form in the absence of inhibitors. CONCLUSION Partial dissociation of NS2B from NS3 has implications for the way in which the NS3 protease can be positioned with respect to the host cell membrane when NS2B is membrane associated via N- and C-terminal segments present in the polyprotein. In the case of the West Nile virus protease...

OBJECTIVES: West Nile virus (Flavivirus: Flaviviridae; WNV) has spread rapidly throughout the Caribbean Basin since its initial detection there in 2001. This report summarizes our current knowledge of WNV transmission in tropical America. METHODS: We reviewed the published literature and consulted with key public health officials to obtain unpublished data. RESULTS: West Nile virus infections first appeared in human residents of the Cayman Islands and the Florida Keys in 2001, and in apparently healthy Jamaican birds sampled early in 2002. Serologic evidence of WNV infection in 2002 was detected in horses, chickens and resident free-ranging birds in Guadeloupe, the Dominican Republic, and eastern Mexico. In 2003, WNV spread in Mexico and northern Central America, and serologic evidence was detected in the Bahamas, Puerto Rico and Cuba. In 2004, the first serologic evidence of WNV activity in South American ecosystems surfaced in September-October in Colombia and Trinidad, where domestic animals circulated WNV-neutralizing antibodies. CONCLUSIONS: The sparse reports of equine, human and avian disease in Latin America and the Caribbean is puzzling. Isolates are needed to evaluate viral attenuation or other possible explanations for reduced disease burden in tropical ecosystems.