International Journal of Environmental Research and Public Health

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Open AccessArticle

The Incidence of West Nile Disease in Russia in Relation to Climatic and Environmental Factors

by Alexander E. Platonov, Vladimir A. Tolpin, Kristina A. Gridneva, Anton V. Titkov, Olga V. Platonova, Nadezhda M. Kolyasnikova, Luca Busani and Giovanni Rezza

Int. J. Environ. Res. Public Health 2014, 11(2), 1211-1232; https://doi.org/10.3390/ijerph110201211 - 23 Jan 2014

Cited by 19 | Viewed by 8129

Abstract

Since 1999, human cases of West Nile fever/neuroinvasive disease (WND) have been reported annually in Russia. The highest incidence has been recorded in three provinces of southern European Russia (Volgograd, Astrakhan and Rostov Provinces), yet in 2010–2012 the distribution of human cases expanded [...] Read more.

Since 1999, human cases of West Nile fever/neuroinvasive disease (WND) have been reported annually in Russia. The highest incidence has been recorded in three provinces of southern European Russia (Volgograd, Astrakhan and Rostov Provinces), yet in 2010–2012 the distribution of human cases expanded northwards considerably. From year to year, the number of WND cases varied widely, with major WND outbreaks in 1999, 2007, 2010, and 2012. The present study was aimed at identifying the most important climatic and environmental factors potentially affecting WND incidence in the three above-mentioned provinces and at building simple prognostic models, using those factors, by the decision trees method. The effects of 96 variables, including mean monthly temperature, relative humidity, precipitation, Normalized Difference Vegetation Index, etc. were taken into account. The findings of this analysis show that an increase of human WND incidence, compared to the previous year, was mostly driven by higher temperatures in May and/or in June, as well as (to a lesser extent) by high August-September temperatures. Declining incidence was associated with cold winters (December and/or January, depending on the region and type of model). WND incidence also tended to decrease during year following major WND outbreaks. Combining this information, the future trend of WND may be, to some extent, predicted, in accordance with the climatic conditions observed before the summer peak of WND incidence. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

Integrated Human Surveillance Systems of West Nile Virus Infections in Italy: The 2012 Experience

by Christian Napoli, Antonino Bella, Silvia Declich, Giuliano Grazzini, Letizia Lombardini, Alessandro Nanni Costa, Loredana Nicoletti, Maria Grazia Pompa, Simonetta Pupella, Francesca Russo and Caterina Rizzo

Int. J. Environ. Res. Public Health 2013, 10(12), 7180-7192; https://doi.org/10.3390/ijerph10127180 - 13 Dec 2013

Cited by 16 | Viewed by 7349

Abstract

In Italy, a West Nile virus (WNV) surveillance plan was firstly implemented in 2008 and 2009 in two affected regions and, since 2010, according to a national plan, a WNV neuroinvasive disease (WNND) surveillance has to be carried out each year during the [...] Read more.

In Italy, a West Nile virus (WNV) surveillance plan was firstly implemented in 2008 and 2009 in two affected regions and, since 2010, according to a national plan, a WNV neuroinvasive disease (WNND) surveillance has to be carried out each year during the period 15 June–30 November, in those regions where WNV circulation has been demonstrated among humans, animals or vectors. Moreover, since WNV can be transmitted to humans even by blood transfusions and organ transplants obtained from infected donors, the national surveillance integrates the blood transfusions and organs transplant surveillances too. The paper describes the results of this integrated human surveillance in Italy in 2012. Overall, in 2012, 28 autochthonous confirmed cases of WNND were reported, 14 blood donations were found WNV positive by Nucleic Acid Amplification Test and no solid organ donors tested positive for WNV. Moreover, 17 cases of WNV fever were confirmed in Veneto region. When comparing the number of WNND cases reported to the surveillance system in previous 4 years (43 cases during the period 2008–2011), with those reported in 2012 an important increase was observed in 2012. The geographic distribution of human cases was consistent with the WNV circulation among animals and vectors. Moreover, the implementation of preventive measures for WNV transmission through blood components allowed the detection of blood donors positive for WNV, avoiding the further spread of the disease. Since surveillance strategies and preventive measures are based on the integration among human, animal and vector control activities, the Italian experience could be considered a good example of collaboration among different sectors of public health in a “one health” perspective. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

Vector Contact Rates on Eastern Bluebird Nestlings Do Not Indicate West Nile Virus Transmission in Henrico County, Virginia, USA

by Kevin A. Caillouët, Charles W. Robertson, David C. Wheeler, Nicholas Komar and Lesley P. Bulluck

Int. J. Environ. Res. Public Health 2013, 10(12), 6366-6379; https://doi.org/10.3390/ijerph10126366 - 27 Nov 2013

Cited by 4 | Viewed by 6498

Abstract

Sensitive indicators of spatial and temporal variation in vector-host contact rates are critical to understanding the transmission and eventual prevention of arboviruses such as West Nile virus (WNV). Monitoring vector contact rates on particularly susceptible and perhaps more exposed avian nestlings may provide [...] Read more.

Sensitive indicators of spatial and temporal variation in vector-host contact rates are critical to understanding the transmission and eventual prevention of arboviruses such as West Nile virus (WNV). Monitoring vector contact rates on particularly susceptible and perhaps more exposed avian nestlings may provide an advanced indication of local WNV amplification. To test this hypothesis we monitored WNV infection and vector contact rates among nestlings occupying nest boxes (primarily Eastern bluebirds; Sialia sialis, Turdidae) across Henrico County, Virginia, USA, from May to August 2012. Observed host-seeking rates were temporally variable and associated with absolute vector and host abundances. Despite substantial effort to monitor WNV among nestlings and mosquitoes, we did not detect the presence of WNV in these populations. Generally low vector-nestling host contact rates combined with the negative WNV infection data suggest that monitoring transmission parameters among nestling Eastern bluebirds in Henrico County, Virginia, USA may not be a sensitive indicator of WNV activity. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

Spatio-Temporal Epidemiology of Human West Nile Virus Disease in South Dakota

by Michael C. Wimberly, Paolla Giacomo, Lon Kightlinger and Michael B. Hildreth

Int. J. Environ. Res. Public Health 2013, 10(11), 5584-5602; https://doi.org/10.3390/ijerph10115584 - 29 Oct 2013

Cited by 20 | Viewed by 8634

Abstract

Despite a cold temperate climate and low human population density, the Northern Great Plains has become a persistent hot spot for human West Nile virus (WNV) disease in North America. Understanding the spatial and temporal patterns of WNV can provide insights into the [...] Read more.

Despite a cold temperate climate and low human population density, the Northern Great Plains has become a persistent hot spot for human West Nile virus (WNV) disease in North America. Understanding the spatial and temporal patterns of WNV can provide insights into the epidemiological and ecological factors that influence disease emergence and persistence. We analyzed the 1,962 cases of human WNV disease that occurred in South Dakota from 2002–2012 to identify the geographic distribution, seasonal cycles, and interannual variability of disease risk. The geographic and seasonal patterns of WNV have changed since the invasion and initial epidemic in 2002–2003, with cases shifting toward the eastern portion of South Dakota and occurring earlier in the transmission season in more recent years. WNV cases were temporally autocorrelated at lags of up to six weeks and early season cumulative case numbers were correlated with seasonal totals, indicating the possibility of using these data for short-term early detection of outbreaks. Epidemiological data are likely to be most effective for early warning of WNV virus outbreaks if they are integrated with entomological surveillance and environmental monitoring to leverage the strengths and minimize the weaknesses of each information source. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

West Nile Virus Transmission in Sentinel Chickens and Potential Mosquito Vectors, Senegal River Delta, 2008–2009

by Assane Gueye Fall, Amadou Diaïté, Momar Talla Seck, Jérémy Bouyer, Thierry Lefrançois, Nathalie Vachiéry, Rosalie Aprelon, Ousmane Faye, Lassana Konaté and Renaud Lancelot

Int. J. Environ. Res. Public Health 2013, 10(10), 4718-4727; https://doi.org/10.3390/ijerph10104718 - 1 Oct 2013

Cited by 19 | Viewed by 8725

Abstract

West Nile virus (WNV) is an arthropod-borne Flavivirus usually transmitted to wild birds by Culex mosquitoes. Humans and horses are susceptible to WNV but are dead-end hosts. WNV is endemic in Senegal, particularly in the Senegal River Delta. To assess transmission patterns and [...] Read more.

West Nile virus (WNV) is an arthropod-borne Flavivirus usually transmitted to wild birds by Culex mosquitoes. Humans and horses are susceptible to WNV but are dead-end hosts. WNV is endemic in Senegal, particularly in the Senegal River Delta. To assess transmission patterns and potential vectors, entomological and sentinel serological was done in Ross Bethio along the River Senegal. Three sentinel henhouses (also used as chicken-baited traps) were set at 100 m, 800 m, and 1,300 m from the river, the latter close to a horse-baited trap. Blood samples were taken from sentinel chickens at 2-week intervals. Seroconversions were observed in sentinel chickens in November and December. Overall, the serological incidence rate was 4.6% with 95% confidence interval (0.9; 8.4) in the sentinel chickens monitored for this study. Based on abundance pattern, Culex neavei was the most likely mosquito vector involved in WNV transmission to sentinel chickens, and a potential bridge vector between birds and mammals. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

Genetic Analysis of West Nile Virus Isolates from an Outbreak in Idaho, United States, 2006–2007

by Andriyan Grinev, Caren Chancey, Germán Añez, Christopher Ball, Valerie Winkelman, Phillip Williamson, Gregory A. Foster, Susan L. Stramer and Maria Rios

Int. J. Environ. Res. Public Health 2013, 10(9), 4486-4506; https://doi.org/10.3390/ijerph10094486 - 23 Sep 2013

Cited by 3 | Viewed by 6942

Abstract

West Nile virus (WNV) appeared in the U.S. in 1999 and has since become endemic, with yearly summer epidemics causing tens of thousands of cases of serious disease over the past 14 years. Analysis of WNV strains isolated during the 2006–2007 epidemic seasons [...] Read more.

West Nile virus (WNV) appeared in the U.S. in 1999 and has since become endemic, with yearly summer epidemics causing tens of thousands of cases of serious disease over the past 14 years. Analysis of WNV strains isolated during the 2006–2007 epidemic seasons demonstrates that a new genetic variant had emerged coincidentally with an intense outbreak in Idaho during 2006. The isolates belonging to the new variant carry a 13 nt deletion, termed ID-Δ13, located at the variable region of the 3′UTR, and are genetically related. The analysis of deletions and insertions in the 3′UTR of two major lineages of WNV revealed the presence of conserved repeats and two indel motifs in the variable region of the 3′UTR. One human and two bird isolates from the Idaho 2006–2007 outbreaks were sequenced using Illumina technology and within-host variability was analyzed. Continued monitoring of new genetic variants is important for public health as WNV continues to evolve. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

Natural Exposure of Horses to Mosquito-Borne Flaviviruses in South-East Queensland, Australia

by Natalie A. Prow, Cindy S. E. Tan, Wenqi Wang, Jody Hobson-Peters, Lisa Kidd, Anita Barton, John Wright, Roy A. Hall and Helle Bielefeldt-Ohmann

Int. J. Environ. Res. Public Health 2013, 10(9), 4432-4443; https://doi.org/10.3390/ijerph10094432 - 17 Sep 2013

Cited by 27 | Viewed by 8437

Abstract

In 2011 an unprecedented epidemic of equine encephalitis occurred in south-eastern (SE) Australia following heavy rainfall and severe flooding in the preceding 2–4 months. Less than 6% of the documented cases occurred in Queensland, prompting the question of pre-existing immunity in Queensland horses. [...] Read more.

In 2011 an unprecedented epidemic of equine encephalitis occurred in south-eastern (SE) Australia following heavy rainfall and severe flooding in the preceding 2–4 months. Less than 6% of the documented cases occurred in Queensland, prompting the question of pre-existing immunity in Queensland horses. A small-scale serological survey was conducted on horses residing in one of the severely flood-affected areas of SE-Queensland. Using a flavivirus-specific blocking-ELISA we found that 63% (39/62) of horses older than 3 years were positive for flavivirus antibodies, and of these 18% (7/38) had neutralizing antibodies to Murray Valley encephalitis virus (MVEV), Kunjin virus (WNV_KUN) and/or Alfuy virus (ALFV). The remainder had serum-neutralizing antibodies to viruses in the Kokobera virus (KOKV) complex or antibodies to unknown/untested flaviviruses. Amongst eight yearlings one presented with clinical MVEV-encephalomyelitis, while another, clinically normal, had MVEV-neutralizing antibodies. The remaining six yearlings were flavivirus antibody negative. Of 19 foals born between August and November 2011 all were flavivirus antibody negative in January 2012. This suggests that horses in the area acquire over time active immunity to a range of flaviviruses. Nevertheless, the relatively infrequent seropositivity to MVEV, WNV_KUN and ALFV (15%) suggests that factors other than pre-existing immunity may have contributed to the low incidence of arboviral disease in SE-Queensland horses during the 2011 epidemic. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

Using Undergraduate Researchers to Build Vector and West Nile Virus Surveillance Capacity

by Grant Hokit, Sam Alvey, Jennifer M. O. Geiger, Gregory D. Johnson, Marni G. Rolston, Daniel T. Kinsey and Neva Tall Bear

Int. J. Environ. Res. Public Health 2013, 10(8), 3192-3202; https://doi.org/10.3390/ijerph10083192 - 31 Jul 2013

Cited by 4 | Viewed by 5906

Abstract

Vector surveillance for infectious diseases is labor intensive and constantly threatened by budget decisions. We report on outcomes of an undergraduate research experience designed to build surveillance capacity for West Nile Virus (WNV) in Montana (USA). Students maintained weekly trapping stations for mosquitoes [...] Read more.

Vector surveillance for infectious diseases is labor intensive and constantly threatened by budget decisions. We report on outcomes of an undergraduate research experience designed to build surveillance capacity for West Nile Virus (WNV) in Montana (USA). Students maintained weekly trapping stations for mosquitoes and implemented assays to test for WNV in pools of Culex tarsalis. Test results were verified in a partnership with the state health laboratory and disseminated to the ArboNET Surveillance System. Combined with prior surveillance data, Cx. tarsalis accounted for 12% of mosquitoes with a mean capture rate of 74 (±SD = 118) Cx. tarsalis females per trap and a minimum infection rate of 0.3 infected mosquitoes per 1000 individuals. However, capture and infection rates varied greatly across years and locations. Infection rate, but not capture rate, was positively associated with the number of WNV human cases (Spearman’s rho = 0.94, p < 0.001). In most years, detection of the first positive mosquito pool occurred at least a week prior to the first reported human case. We suggest that undergraduate research can increase vector surveillance capacity while providing effective learning opportunities for students. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

Use of Competition ELISA for Monitoring of West Nile Virus Infections in Horses in Germany

by Ute Ziegler, Joke Angenvoort, Christine Klaus, Uschi Nagel-Kohl, Claudia Sauerwald, Sabine Thalheim, Steffen Horner, Bettina Braun, Susanne Kenklies, Judith Tyczka, Markus Keller and Martin H. Groschup

Int. J. Environ. Res. Public Health 2013, 10(8), 3112-3120; https://doi.org/10.3390/ijerph10083112 - 24 Jul 2013

Cited by 28 | Viewed by 9051

Abstract

West Nile virus (WNV) is a mosquito-borne viral pathogen of global importance and is considered to be the most widespread flavivirus in the World. Horses, as dead-end hosts, can be infected by bridge mosquito vectors and undergo either subclinical infections or develop severe [...] Read more.

West Nile virus (WNV) is a mosquito-borne viral pathogen of global importance and is considered to be the most widespread flavivirus in the World. Horses, as dead-end hosts, can be infected by bridge mosquito vectors and undergo either subclinical infections or develop severe neurological diseases. The aim of this study was to detect WNV specific antibodies in horses in Germany as an indicator for an endemic circulation of WNV. Sera from more than 5,000 horses (primarily fallen stock animals) were collected in eight different federal states of Germany from 2010 to 2012. Sera were screened by a competitive ELISA and positive reactions were verified by an indirect IgM ELISA and/or by virus neutralization tests (VNT) for WNV and Tick-borne encephalitis virus (TBEV) in order to exclude cross-reacting antibody reactions. In essence WNV specific antibodies could not be detected in any of the horse sera. Not surprisingly, a small number of sera contained antibodies against TBEV. It is noteworthy that equine sera were often collected from horse carcasses and therefore were of poor quality. Nonetheless, these sera were still suitable for WNV ELISA testing, i.e., they did not produce a high background reaction which is a frequently observed phenomenon. According to these data there is no evidence for indigenous WNV infections in horses in Germany at present. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

Climate Change and West Nile Virus in a Highly Endemic Region of North America

by Chen C. Chen, Emily Jenkins, Tasha Epp, Cheryl Waldner, Philip S. Curry and Catherine Soos

Int. J. Environ. Res. Public Health 2013, 10(7), 3052-3071; https://doi.org/10.3390/ijerph10073052 - 22 Jul 2013

Cited by 40 | Viewed by 11886

Abstract

The Canadian prairie provinces of Manitoba, Saskatchewan, and Alberta have reported the highest human incidence of clinical cases of West Nile virus (WNV) infection in Canada. The primary vector for WVN in this region is the mosquito Culex tarsalis. This study used constructed [...] Read more.

The Canadian prairie provinces of Manitoba, Saskatchewan, and Alberta have reported the highest human incidence of clinical cases of West Nile virus (WNV) infection in Canada. The primary vector for WVN in this region is the mosquito Culex tarsalis. This study used constructed models and biological thresholds to predict the spatial and temporal distribution of Cx. tarsalis and WNV infection rate in the prairie provinces under a range of potential future climate and habitat conditions. We selected one median and two extreme outcome scenarios to represent future climate conditions in the 2020 (2010–2039), 2050 (2040–2069) and 2080 (2070–2099) time slices. In currently endemic regions, the projected WNV infection rate under the median outcome scenario in 2050 raised 17.91 times (ranged from 1.29–27.45 times for all scenarios and time slices) comparing to current climate conditions. Seasonal availability of Cx. tarsalis infected with WNV extended from June to August to include May and September. Moreover, our models predicted northward range expansion for Cx. tarsalis (1.06–2.56 times the current geographic area) and WNV (1.08–2.34 times the current geographic area). These findings predict future public and animal health risk of WNV in the Canadian prairie provinces. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessArticle

Modeling Monthly Variation of Culex tarsalis (Diptera: Culicidae) Abundance and West Nile Virus Infection Rate in the Canadian Prairies

by Chen-Chih Chen, Tasha Epp, Emily Jenkins, Cheryl Waldner, Philip S. Curry and Catherine Soos

Int. J. Environ. Res. Public Health 2013, 10(7), 3033-3051; https://doi.org/10.3390/ijerph10073033 - 22 Jul 2013

Cited by 19 | Viewed by 7954

Abstract

The Canadian prairie provinces of Alberta, Saskatchewan, and Manitoba have generally reported the highest human incidence of West Nile virus (WNV) in Canada. In this study, environmental and biotic factors were used to predict numbers of Culex tarsalis Coquillett, which is the primary [...] Read more.

The Canadian prairie provinces of Alberta, Saskatchewan, and Manitoba have generally reported the highest human incidence of West Nile virus (WNV) in Canada. In this study, environmental and biotic factors were used to predict numbers of Culex tarsalis Coquillett, which is the primary mosquito vector of WNV in this region, and prevalence of WNV infection in Cx. tarsalis in the Canadian prairies. The results showed that higher mean temperature and elevated time lagged mean temperature were associated with increased numbers of Cx. tarsalis and higher WNV infection rates. However, increasing precipitation was associated with higher abundance of Cx. tarsalis and lower WNV infection rate. In addition, this study found that increased temperature fluctuation and wetland land cover were associated with decreased infection rate in the Cx. tarsalis population. The resulting monthly models can be used to inform public health interventions by improving the predictions of population abundance of Cx. tarsalis and the transmission intensity of WNV in the Canadian prairies. Furthermore, these models can also be used to examine the potential effects of climate change on the vector population abundance and the distribution of WNV. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Review

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Open AccessReview

Predictive Modeling of West Nile Virus Transmission Risk in the Mediterranean Basin: How Far from Landing?

by Véronique Chevalier, Annelise Tran and Benoit Durand

Int. J. Environ. Res. Public Health 2014, 11(1), 67-90; https://doi.org/10.3390/ijerph110100067 - 20 Dec 2013

Cited by 40 | Viewed by 10424

Abstract

The impact on human and horse health of West Nile fever (WNF) recently and dramatically increased in Europe and neighboring countries. Involving several mosquito and wild bird species, WNF epidemiology is complex. Despite the implementation of surveillance systems in several countries of concern, [...] Read more.

The impact on human and horse health of West Nile fever (WNF) recently and dramatically increased in Europe and neighboring countries. Involving several mosquito and wild bird species, WNF epidemiology is complex. Despite the implementation of surveillance systems in several countries of concern, and due to a lack of knowledge, outbreak occurrence remains unpredictable. Statistical models may help identifying transmission risk factors. When spatialized, they provide tools to identify areas that are suitable for West Nile virus transmission. Mathematical models may be used to improve our understanding of epidemiological process involved, to evaluate the impact of environmental changes or test the efficiency of control measures. We propose a systematic literature review of publications aiming at modeling the processes involved in WNF transmission in the Mediterranean Basin. The relevance of the corresponding models as predictive tools for risk mapping, early warning and for the design of surveillance systems in a changing environment is analyzed. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessReview

Increased Pathogenicity of West Nile Virus (WNV) by Glycosylation of Envelope Protein and Seroprevalence of WNV in Wild Birds in Far Eastern Russia

by Hiroaki Kariwa, Ryo Murata, Masashi Totani, Kentaro Yoshii and Ikuo Takashima

Int. J. Environ. Res. Public Health 2013, 10(12), 7144-7164; https://doi.org/10.3390/ijerph10127144 - 12 Dec 2013

Cited by 9 | Viewed by 7230

Abstract

In this review, we discuss the possibility that the glycosylation of West Nile (WN) virus E-protein may be associated with enhanced pathogenicity and higher replication of WN virus. The results indicate that E-protein glycosylation allows the virus to multiply in a heat-stable manner [...] Read more.

In this review, we discuss the possibility that the glycosylation of West Nile (WN) virus E-protein may be associated with enhanced pathogenicity and higher replication of WN virus. The results indicate that E-protein glycosylation allows the virus to multiply in a heat-stable manner and therefore, has a critical role in enhanced viremic levels and virulence of WN virus in young-chick infection model. The effect of the glycosylation of the E protein on the pathogenicity of WN virus in young chicks was further investigated. The results indicate that glycosylation of the WN virus E protein is important for viral multiplication in peripheral organs and that it is associated with the strong pathogenicity of WN virus in birds. The micro-focus reduction neutralization test (FRNT) in which a large number of serum samples can be handled at once with a small volume (15 μL) of serum was useful for differential diagnosis between Japanese encephalitis and WN virus infections in infected chicks. Serological investigation was performed among wild birds in the Far Eastern region of Russia using the FRNT. Antibodies specific to WN virus were detected in 21 samples of resident and migratory birds out of 145 wild bird samples in the region. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessReview

West Nile Virus State of the Art Report of MALWEST Project

by Andriani Marka, Alexandros Diamantidis, Anna Papa, George Valiakos, Serafeim C. Chaintoutis, Dimitrios Doukas, Persefoni Tserkezou, Alexios Giannakopoulos, Konstantinos Papaspyropoulos, Eleni Patsoula, Evangelos Badieritakis, Agoritsa Baka, Maria Tseroni, Danai Pervanidou, Nikos T. Papadopoulos, George Koliopoulos, Dimitrios Tontis, Chrysostomos I. Dovas, Charalambos Billinis, Athanassios Tsakris, Jenny Kremastinou, Christos Hadjichristodoulou and For The MALWEST Project Show full author list Hide full author list

Int. J. Environ. Res. Public Health 2013, 10(12), 6534-6610; https://doi.org/10.3390/ijerph10126534 - 2 Dec 2013

Cited by 30 | Viewed by 14783

Abstract

During the last three years Greece is experiencing the emergence of West Nile virus (WNV) epidemics. Within this framework, an integrated surveillance and control programme (MALWEST project) with thirteen associate partners was launched aiming to investigate the disease and suggest appropriate interventions. One [...] Read more.

During the last three years Greece is experiencing the emergence of West Nile virus (WNV) epidemics. Within this framework, an integrated surveillance and control programme (MALWEST project) with thirteen associate partners was launched aiming to investigate the disease and suggest appropriate interventions. One out of seven work packages of the project is dedicated to the State of the Art report for WNV. Three expert working groups on humans, animals and mosquitoes were established. Medical databases (PubMed, Scopus) were searched together with websites: e.g., WHO, CDC, ECDC. In total, 1,092 relevant articles were initially identified and 258 of them were finally included as references regarding the current knowledge about WNV, along with 36 additional sources (conference papers, reports, book chapters). The review is divided in three sections according to the fields of interest: (1) WNV in humans (epidemiology, molecular characteristics, transmission, diagnosis, treatment, prevention, surveillance); (2) WNV in animals (epidemiological and transmission characteristics concerning birds, horses, reptiles and other animal species) and (3) WNV in mosquitoes (control, surveillance). Finally, some examples of integrated surveillance programmes are presented. The introduction and establishment of the disease in Greece and other European countries further emphasizes the need for thorough research and broadening of our knowledge on this viral pathogen. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessReview

The Changing Epidemiology of Kunjin Virus in Australia

by Natalie A. Prow

Int. J. Environ. Res. Public Health 2013, 10(12), 6255-6272; https://doi.org/10.3390/ijerph10126255 - 25 Nov 2013

Cited by 42 | Viewed by 9629

Abstract

West Nile virus (WNV) is a mosquito-borne virus responsible for outbreaks of viral encephalitis in humans and horses, with particularly virulent strains causing recent outbreaks of disease in Eastern Europe, the Middle East and North America. A strain of WNV, Kunjin (WNV_KUN [...] Read more.

West Nile virus (WNV) is a mosquito-borne virus responsible for outbreaks of viral encephalitis in humans and horses, with particularly virulent strains causing recent outbreaks of disease in Eastern Europe, the Middle East and North America. A strain of WNV, Kunjin (WNV_KUN), is endemic in northern Australia and infection with this virus is generally asymptomatic. However in early 2011, an unprecedented outbreak of encephalitis in horses occurred in south-eastern Australia, resulting in mortality in approximately 10%–15% of infected horses. A WNV-like virus (WNV_NSW2011) was isolated and found to be most closely related to the indigenous WNV_KUN, rather than other exotic WNV strains. Furthermore, at least two amino acid changes associated with increased virulence of the North American New York 99 strain (WNV_NY99) compared to the prototype WNV_KUN were present in the WNV_NSW2011 sequence. This review summarizes our current understanding of WNV_KUN and how the epidemiology and ecology of this virus has changed. Analysis of virulence determinants of contemporary WNV_KUN isolates will provide clues on where virulent strains have emerged in Australia. A better understanding of the changing ecology and epidemiology associated with the emergence of virulent strains is essential to prepare for future outbreaks of WNV disease in Australia. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessReview

Flaviviruses in Europe: Complex Circulation Patterns and Their Consequences for the Diagnosis and Control of West Nile Disease

by Cécile Beck, Miguel Angel Jimenez-Clavero, Agnès Leblond, Benoît Durand, Norbert Nowotny, Isabelle Leparc-Goffart, Stéphan Zientara, Elsa Jourdain and Sylvie Lecollinet

Int. J. Environ. Res. Public Health 2013, 10(11), 6049-6083; https://doi.org/10.3390/ijerph10116049 - 12 Nov 2013

Cited by 149 | Viewed by 18454

Abstract

In Europe, many flaviviruses are endemic (West Nile, Usutu, tick-borne encephalitis viruses) or occasionally imported (dengue, yellow fever viruses). Due to the temporal and geographical co-circulation of flaviviruses in Europe, flavivirus differentiation by diagnostic tests is crucial in the adaptation of surveillance and [...] Read more.

In Europe, many flaviviruses are endemic (West Nile, Usutu, tick-borne encephalitis viruses) or occasionally imported (dengue, yellow fever viruses). Due to the temporal and geographical co-circulation of flaviviruses in Europe, flavivirus differentiation by diagnostic tests is crucial in the adaptation of surveillance and control efforts. Serological diagnosis of flavivirus infections is complicated by the antigenic similarities among the Flavivirus genus. Indeed, most flavivirus antibodies are directed against the highly immunogenic envelope protein, which contains both flavivirus cross-reactive and virus-specific epitopes. Serological assay results should thus be interpreted with care and confirmed by comparative neutralization tests using a panel of viruses known to circulate in Europe. However, antibody cross-reactivity could be advantageous in efforts to control emerging flaviviruses because it ensures partial cross-protection. In contrast, it might also facilitate subsequent diseases, through a phenomenon called antibody-dependent enhancement mainly described for dengue virus infections. Here, we review the serological methods commonly used in WNV diagnosis and surveillance in Europe. By examining past and current epidemiological situations in different European countries, we present the challenges involved in interpreting flavivirus serological tests and setting up appropriate surveillance programs; we also address the consequences of flavivirus circulation and vaccination for host immunity. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Open AccessReview

Exploring the Spatio-Temporal Dynamics of Reservoir Hosts, Vectors, and Human Hosts of West Nile Virus: A Review of the Recent Literature

by Esra Ozdenerol, Gregory N. Taff and Cem Akkus

Int. J. Environ. Res. Public Health 2013, 10(11), 5399-5432; https://doi.org/10.3390/ijerph10115399 - 25 Oct 2013

Cited by 28 | Viewed by 11231

Abstract

Over the last two decades West Nile Virus (WNV) has been responsible for significant disease outbreaks in humans and animals in many parts of the World. Its extremely rapid global diffusion argues for a better understanding of its geographic extent. The purpose of [...] Read more.

Over the last two decades West Nile Virus (WNV) has been responsible for significant disease outbreaks in humans and animals in many parts of the World. Its extremely rapid global diffusion argues for a better understanding of its geographic extent. The purpose of this inquiry was to explore spatio-temporal patterns of WNV using geospatial technologies to study populations of the reservoir hosts, vectors, and human hosts, in addition to the spatio-temporal interactions among these populations. Review of the recent literature on spatial WNV disease risk modeling led to the conclusion that numerous environmental factors might be critical for its dissemination. New Geographic Information Systems (GIS)-based studies are monitoring occurrence at the macro-level, and helping pinpoint areas of occurrence at the micro-level, where geographically-targeted, species-specific control measures are sometimes taken and more sophisticated methods of surveillance have been used. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Molecular Epidemiology and Evolution of West Nile Virus in North America

by Brian R. Mann, Allison R. McMullen, Daniele M. Swetnam and Alan D. T. Barrett

Int. J. Environ. Res. Public Health 2013, 10(10), 5111-5129; https://doi.org/10.3390/ijerph10105111 - 16 Oct 2013

Cited by 44 | Viewed by 9591

Abstract

West Nile virus (WNV) was introduced to New York in 1999 and rapidly spread throughout North America and into parts of Central and South America. Displacement of the original New York (NY99) genotype by the North America/West Nile 2002 (NA/WN02) genotype occurred in [...] Read more.

West Nile virus (WNV) was introduced to New York in 1999 and rapidly spread throughout North America and into parts of Central and South America. Displacement of the original New York (NY99) genotype by the North America/West Nile 2002 (NA/WN02) genotype occurred in 2002 with subsequent identification of a novel genotype in 2003 in isolates collected from the southwestern Unites States region (SW/WN03 genotype). Both genotypes co-circulate to date. Subsequent WNV surveillance studies have confirmed additional genotypes in the United States that have become extinct due to lack of a selective advantage or stochastic effect; however, the dynamic emergence, displacement, and extinction of multiple WNV genotypes in the US from 1999–2012 indicates the continued evolution of WNV in North America. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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European Surveillance for West Nile Virus in Mosquito Populations

by Olivier Engler, Giovanni Savini, Anna Papa, Jordi Figuerola, Martin H. Groschup, Helge Kampen, Jolyon Medlock, Alexander Vaux, Anthony J. Wilson, Doreen Werner, Hanna Jöst, Maria Goffredo, Gioia Capelli, Valentina Federici, Mauro Tonolla, Nicola Patocchi, Eleonora Flacio, Jasmine Portmann, Anya Rossi-Pedruzzi, Spiros Mourelatos, Santiago Ruiz, Ana Vázquez, Mattia Calzolari, Paolo Bonilauri, Michele Dottori, Francis Schaffner, Alexander Mathis and Nicholas Johnson Show full author list Hide full author list

Int. J. Environ. Res. Public Health 2013, 10(10), 4869-4895; https://doi.org/10.3390/ijerph10104869 - 11 Oct 2013

Cited by 147 | Viewed by 17418

Abstract

A wide range of arthropod-borne viruses threaten both human and animal health either through their presence in Europe or through risk of introduction. Prominent among these is West Nile virus (WNV), primarily an avian virus, which has caused multiple outbreaks associated with human [...] Read more.

A wide range of arthropod-borne viruses threaten both human and animal health either through their presence in Europe or through risk of introduction. Prominent among these is West Nile virus (WNV), primarily an avian virus, which has caused multiple outbreaks associated with human and equine mortality. Endemic outbreaks of West Nile fever have been reported in Italy, Greece, France, Romania, Hungary, Russia and Spain, with further spread expected. Most outbreaks in Western Europe have been due to infection with WNV Lineage 1. In Eastern Europe WNV Lineage 2 has been responsible for human and bird mortality, particularly in Greece, which has experienced extensive outbreaks over three consecutive years. Italy has experienced co-circulation with both virus lineages. The ability to manage this threat in a cost-effective way is dependent on early detection. Targeted surveillance for pathogens within mosquito populations offers the ability to detect viruses prior to their emergence in livestock, equine species or human populations. In addition, it can establish a baseline of mosquito-borne virus activity and allow monitoring of change to this over time. Early detection offers the opportunity to raise disease awareness, initiate vector control and preventative vaccination, now available for horses, and encourage personal protection against mosquito bites. This would have major benefits through financial savings and reduction in equid morbidity/mortality. However, effective surveillance that predicts virus outbreaks is challenged by a range of factors including limited resources, variation in mosquito capture rates (too few or too many), difficulties in mosquito identification, often reliant on specialist entomologists, and the sensitive, rapid detection of viruses in mosquito pools. Surveillance for WNV and other arboviruses within mosquito populations varies between European countries in the extent and focus of the surveillance. This study reviews the current status of WNV in mosquito populations across Europe and how this is informing our understanding of virus epidemiology. Key findings such as detection of virus, presence of vector species and invasive mosquito species are summarized, and some of the difficulties encountered when applying a cost-effective surveillance programme are highlighted. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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The Complex Epidemiological Scenario of West Nile Virus in Italy

by Luisa Barzon, Monia Pacenti, Elisa Franchin, Laura Squarzon, Enrico Lavezzo, Margherita Cattai, Riccardo Cusinato and Giorgio Palù

Int. J. Environ. Res. Public Health 2013, 10(10), 4669-4689; https://doi.org/10.3390/ijerph10104669 - 30 Sep 2013

Cited by 37 | Viewed by 8214

Abstract

Entomological, veterinary, and human surveillance systems for West Nile virus (WNV) infection have been implemented in Italy since the first detection of the virus in 1998. These surveillance activities documented a progressive increase of WNV activity and spread in different regions and the [...] Read more.

Entomological, veterinary, and human surveillance systems for West Nile virus (WNV) infection have been implemented in Italy since the first detection of the virus in 1998. These surveillance activities documented a progressive increase of WNV activity and spread in different regions and the emergence of new WNV lineages and strains. Italy is a paradigmatic example of the complex epidemiology of WNV in Europe, where sporadic cases of WNV infection, clusters, and small outbreaks have been reported in several regions. In addition, different strains of both WNV lineage 1 and lineage 2 have been identified, even co-circulating in the same area. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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A Review of Vaccine Approaches for West Nile Virus

by Arun V. Iyer and Konstantin G. Kousoulas

Int. J. Environ. Res. Public Health 2013, 10(9), 4200-4223; https://doi.org/10.3390/ijerph10094200 - 10 Sep 2013

Cited by 35 | Viewed by 10374

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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The Role of Australian Mosquito Species in the Transmission of Endemic and Exotic West Nile Virus Strains

by Cassie C. Jansen, Scott A. Ritchie and Andrew F. Van den Hurk

Int. J. Environ. Res. Public Health 2013, 10(8), 3735-3752; https://doi.org/10.3390/ijerph10083735 - 19 Aug 2013

Cited by 19 | Viewed by 7501

Abstract

Recent epidemic activity and its introduction into the Western Hemisphere have drawn attention to West Nile virus (WNV) as an international public health problem. Of particular concern has been the ability for the virus to cause outbreaks of disease in highly populated urban [...] Read more.

Recent epidemic activity and its introduction into the Western Hemisphere have drawn attention to West Nile virus (WNV) as an international public health problem. Of particular concern has been the ability for the virus to cause outbreaks of disease in highly populated urban centers. Incrimination of Australian mosquito species is an essential component in determining the receptivity of Australia to the introduction and/or establishment of an exotic strain of WNV and can guide potential management strategies. Based on vector competence experiments and ecological studies, we suggest candidate Australian mosquito species that would most likely be involved in urban transmission of WNV, along with consideration of the endemic WNV subtype, Kunjin. We then examine the interaction of entomological factors with virological and vertebrate host factors, as well as likely mode of introduction, which may influence the potential for exotic WNV to become established and be maintained in urban transmission cycles in Australia. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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Environmental Drivers of West Nile Fever Epidemiology in Europe and Western Asia—A Review

by Shlomit Paz and Jan C. Semenza

Int. J. Environ. Res. Public Health 2013, 10(8), 3543-3562; https://doi.org/10.3390/ijerph10083543 - 9 Aug 2013

Cited by 139 | Viewed by 13848

Abstract

Abiotic and biotic conditions are both important determinants of West Nile Fever (WNF) epidemiology. Ambient temperature plays an important role in the growth rates of vector populations, the interval between blood meals, viral replication rates and transmission of West Nile Virus (WNV). The [...] Read more.

Abiotic and biotic conditions are both important determinants of West Nile Fever (WNF) epidemiology. Ambient temperature plays an important role in the growth rates of vector populations, the interval between blood meals, viral replication rates and transmission of West Nile Virus (WNV). The contribution of precipitation is more complex and less well understood. In this paper we discuss impacts of climatic parameters (temperature, relative humidity, precipitation) and other environmental drivers (such as bird migration, land use) on WNV transmission in Europe. WNV recently became established in southeastern Europe, with a large outbreak in the summer of 2010 and recurrent outbreaks in 2011 and 2012. Abundant competent mosquito vectors, bridge vectors, infected (viremic) migrating and local (amplifying) birds are all important characteristics of WNV transmission. In addition, certain key climatic factors, such as increased ambient temperatures, and by extension climate change, may also favor WNF transmission, and they should be taken into account when evaluating the risk of disease spread in the coming years. Monitoring epidemic precursors of WNF, such as significant temperature deviations in high risk areas, could be used to trigger vector control programs and public education campaigns. Full article

(This article belongs to the Special Issue Epidemiology of West Nile Virus)

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