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Review ArticleThe Global Ecology and Epidemiology of West Nile Virus

Caren Chancey Andriyan Grinev Evgeniya Volkova and Maria Rios

United States Food and Drug Administration Center for Biologics Evaluation and Research Silver Spring MD 20993-0002 USA

Correspondence should be addressed to Maria Rios mariariosfdahhsgov

Received 24 June 2014 Accepted 10 August 2014

Academic Editor Michael J Conway

Copyright copy 2015 Caren Chancey et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Since its initial isolation in Uganda in 1937 through the present West Nile virus (WNV) has become an important cause of humanand animal disease worldwide WNV an enveloped virus of the genus Flavivirus is naturally maintained in an enzootic cyclebetween birds and mosquitoes with occasional epizootic spillover causing disease in humans and horses The mosquito vectorsfor WNV are widely distributed worldwide and the known geographic range of WNV transmission and disease has continuedto increase over the past 77 years While most human infections with WNV are asymptomatic severe neurological disease maydevelop resulting in long-term sequelae or death Surveillance and preventive measures are an ongoing need to reduce the publichealth impact of WNV in areas with the potential for transmission

1 Introduction

First described in 1937 from a febrile illness case in UgandaWestNile virus (WNV) caused infrequent outbreaks typicallyassociated with mild febrile illnesses from the 1950s throughthe 1980s in Israel Egypt India France and South Africa[1ndash11] The first outbreak of neuroinvasive disease caused byWNV (WNND) was reported among the elderly in Israelin 1957 [6 11] Subsequent outbreaks included adult andpediatric WNND cases [4 5 9 12 13]

Starting in the mid-1990s the frequency severity andgeographic range of WNV outbreaks increased and out-breaks of WNV meningitis and encephalitis affecting pri-marily adults struck Bucharest Romania in 1996 VolgogradRussia in 1999 and Israel in 2000 [14ndash16] WNV crossed theAtlantic and reached the western hemisphere in the summerof 1999 when a cluster of patients with encephalitis wasreported in the metropolitan area of New York City NewYork in the United States and within 3 years the virus hadspread to most of the contiguous US and the neighboringcountries of Canada and Mexico In addition although fewhuman cases have been reported WNV has also been foundin Central and South America through surveillance studiesin field specimens suggesting a potential risk for an outbreakin humans [17 18] In the 77 years since its discovery thevirus has propagated to a vast region of the globe and is

now considered the most important causative agent of viralencephalitis worldwide (Figure 1)

2 Viral Genome and Structure

WNV belongs to the genus Flavivirus family Flaviviridaeand is a member of the Japanese encephalitis serocomplexwhich also includes Japanese encephalitis virus St Louisencephalitis virus Rocio virus andMurray Valley encephali-tis virus [19 20] Like other flaviviruses WNV has a single-stranded positive-polarity RNA genome of approximately11 kb containing 10 genes flanked by 51015840 and 31015840 noncod-ing regions (NCR) with no polyadenylation tail at the 31015840end [21ndash25] The NCRs of the WNV genome form stem-loop structures essential for viral replication [26 27] Theviral genome encodes a single polyprotein that is co- andposttranslationally cleaved into 3 structural proteins Capsid(C) Pre-MMembrane (prMM) and Envelope (E) and 7nonstructural (NS) proteins NS1 NS2A NS2B NS3 NS4ANS4B and NS5 [24 28] (Figure 2)

Structurally the WNV virion is a sim50 nm icosahedralparticle surrounded by a lipid bilayer (reviewed in [29])The nucleocapsid is composed of C protein which associateswith the RNA genome and mediates viral assembly [30 31]Heterodimers of prM and E protein become embedded in

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015 Article ID 376230 20 pageshttpdxdoiorg1011552015376230

2 BioMed Research International

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2

3 4

5

2

2

Figure 1 Global distribution of WNV by country Redmdashhuman cases or human seropositivity Bluemdashnonhumanmosquito cases orseropositivity Graymdashno data or no positives reported Black lines represent worldwide distribution of the main WNV mosquito vectorsexcluding areas of extreme climate denoted by dashed lines Circled numbers indicate the reported presence of WNV lineages other thanlineage 1 in that specific area For Japan South Korea Finland and Sweden seropositivity for WNV has been detected only in nonresidentbirds which was not considered indicative of local transmission Kading et al [182] reported infections in gorillas living near the border ofthe Democratic Republic of the Congo and Rwanda which were sampled in the DRC but may have been infected in Rwanda

5998400 UTR C pr M E NS1 a b a b

NS2NS3

NS4NS5

3998400 UTR

Structural Nonstructural

(a)

E-protein dimerMembrane

Capsid proteinprMM protein

RNA

(b)

Figure 2 WNV genome organization and virion composition (a) the viral genome is represented with one ORF encoding 3 structural and 7nonstructural proteins The 51015840 and 31015840 UTRs are indicated Structural proteins are colored green whereas nonstructural proteins are blue (b)Structure of WNV virion

the lipid bilayer of the virus during assembly and are exposedon the virion surface [32]The prM protein is thought to pro-tect the immature virion from undergoing premature fusionprior to viral budding from the cell surface by blocking thefusion loop of E and is cleaved off during the viral maturationprocess [32ndash36] During infection mature immature andpartially mature virus particles are produced containing avarying number of immature prM protein molecules on thesurface [37] The E protein mediates both binding of thereceptor on the cell surface for viral entry and fusion with themembrane of the host cell [38ndash40]

The seven nonstructural proteins are multifunctionalplaying critical roles in viral RNA synthesis andor assembly

NS1 is believed to play an early role in regulation of viralreplication [41ndash43] NS3 has multiple enzymatic functionsserving as a viral serine protease which cleaves the other non-structural proteins from the viral polyprotein in associationwith NS2B an RNA helicase in association with NS4a andan NTPase in association with NS5 [44ndash49]The NS5 proteinis necessary for viral replication containing RNA-dependentRNA polymerase (RdRp) activity in the C-terminal regionand methyltransferase activity in the N-terminal region [4150ndash53] NS2A NS2B NS4A and NS4B are small hydropho-bic proteins that have no known enzymatic functions butare believed to act as cofactors for viral replication complexassembly and localization [54ndash57]

BioMed Research International 3

The WNV NS proteins can also modulate cell signalingand immune responses [58ndash67] In particular the WNVNS1 protein antagonizes the hostrsquos antiviral defenses throughinhibition of TLR3 signal transduction and STAT1STAT2activation [64 67] It has also been shown that NS1 inhibitscomplement activation through fH and C4b binding con-tributing to flavivirus immune evasion [58ndash60] Alternativelycell surface-associated NS1 represents a major target for hostantibodies which contributes to clearance of WNV-infectedcells through Fc-gamma receptor-mediated phagocytosis[61]

3 Genetic Classification

WNV is a genetically and geographically diverse virus Fouror five distinct WNV genetic lineages have been proposedbased on phylogenetic analyses of published isolates [3 68ndash73] Their genomes differ from each other by more than20ndash25 and correlate well with the geographical point ofisolation (Figure 3) Lineages 1 2 and 5 of WNV have beenassociated with significant outbreaks in humans [3 68 72 7475] Lineage 1 is distributed widely throughout the world andconsists of two clades 1a and 1b [76 77] Clade 1a includesisolates from Africa Europe the Middle East Asia and theAmericas Clade 1b is represented by the Australian Kunjinvirus (KUNV)

Phylogeographic analysis has shown that the most prob-able origin of WNV lineage 1a was sub-Saharan or NorthernAfrica [78] This clade emerged in the beginning of the20th century and then spread northwards in the 1970sndash80smainly following the eastern birdmigratory route connectingNorthern Africa and Israel with Russia and Central EuropeLater in the 1990s a strain of WNV genotype 1a appearedin Morocco and Western Europe where the virus becameendemic causing small sporadic outbreaks In 1999 thisWNV lineage 1a virus was exported most likely from theMiddle East to the Americas where it spread over NorthAmerica and then to South America making WNV a globalpublic health problem [78] Zehender et al further dividedclade 1a into A and B subclades with most isolates fromWestern Europe and some from Eastern Europe belongingto subclade A and the remaining Eastern European isolatesbelonging to subclade B [78]

WNV lineage 2 isolates are historically endemic in sub-Saharan Africa and Madagascar and have caused sporadiczoonotic outbreaks in SouthAfrica [71 76 79]More recentlyWNV lineage 2 strains have been associated with bird andhuman outbreaks in southern and eastern Europe [80]Lineage 2 WNV was also sequenced from a 2004 Indonesianclinical specimen [81] It has been suggested that WNVlineage 2 originated in Africa and was introduced intoEurope where it became endemic on at least two separateoccasions during the last two decades [82]

Lineage 3 of WNV is represented by a pair of isolatesfrom mosquitoes collected in the Czech Republic borderregion near Rabensburg Austria in 1997 and 1999 whichhave been shown experimentally to infect only mosquitoesand mosquito cells [68 83] Lineage 4 comprises viruses

circulating in Russia since 1988 including a tick isolate fromthe south-west Caucasus and a number of isolates frommosquitoes and reptiles in the delta of theVolga river [84 85]Lineage 5 formerly considered clade 1c of lineage 1 includesisolates from India from 1955 to the present [3 72 86]

Other potential lineages of WNV have been describedincluding Koutango virus from Africa a group of isolatesfrom Spain a variant of Kunjin virus isolated from SarawakMalaysia and a Senegalese isolate [73 75 87 88]

4 Hosts and Vectors

41 Hosts Maintained in nature in an enzootic transmissioncycle between birds and mosquitoes WNV can also infecthumans and other vertebrates and cause serious disease anddeath (Figure 4) Birds are considered the most importanthosts for the WNV life cycle because they can developviremia sufficiently high to infect mosquitoes (reviewedin [89]) Birds in the family Corvidae such as Americancrows (Corvus brachyrhynchos) and blue jays (Cyanocittacristata) become ill or die from WNV but other birdssuch as common grackles (Quiscalus quiscula) and housesparrows (Passer domesticus) develop high viremiawith lowermortality rates [90] American robins (Turdus migratorius)and house finches (Carpodacus mexicanus) are consideredimportant amplifying hosts in different regions of the US[91] In addition to birds at least 30 other vertebrate speciesincluding reptiles amphibians andmammals are susceptibletoWNV infection However only a few nonavian vertebratesincluding brown lemurs (Lemur fulvus) lake frogs (Ranarinibunda) hamsters fox squirrels (Sciurus niger) easterngray squirrels (Sciurus carolinensis) eastern cottontail rabbits(Sylvilagus floridanus) and eastern chipmunks (Tamias stria-tus) have been reported to develop viremia levels expected tosupport vector transmission [89 92ndash98] Humans and horsesmay suffer serious disease or death fromWNV infection butare considered incidental hosts which do not participate inthe WNV lifecycle because they do not develop sufficientviremia to infect mosquito vectors (reviewed in [89])

Although transmission between hosts bymosquitoes is byfar the most common route of transmission WNV can alsobe transmitted directly if infected animals or mosquitoes areconsumed by susceptible hosts or if susceptible birds come inclose contact with cloacal or oral fluids from other birds withhigh WNV viremia [89]

WNV can also be transmitted between humans by bloodtransfusion organ transplantation transplacental transmis-sion and via breast milk [99ndash103] Although blood donationsin the United States have been screened for WNV by nucleicacid testing since 2003 thirteen instances of transfusion-associated transmission have occurred most recently in 2012[104ndash107]

42 Vectors Mosquitoes are the vector for natural trans-mission of WNV After a mosquito feeds on an infectedcompetent host the arbovirus replicates within the mosquitoand can then be transmitted to a susceptible host throughsalivary gland secretions (Figure 4) Compared to related


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57

AF196835 (USA)AY660002 (Mexico)AF481864 (Israel)DQ118127 (Hungary)

AY278442 (Russia)FJ766332 (Spain)GU011992 (Italy)

GQ851606 (Senegal)EU081844 (Egypt)

AY274505 (Australia)GQ851603 (Australia)

DQ256376 (India)HM147822 (South Africa)

AY688948 (Israel)HM147823 (Madagascar)

EF429200 (South Africa)HM147824 (DRCongo)

HQ537483 (Greece)JN858070 (Italy)

AY765264 (Czech Republic)AY277251 (Russia)FJ159130 (Russia)

EU082200 (Koutango virus Senegal)NC006551 (Usutu virus Austria)

Lineage 1a

Lineage 1b

Lineage 51c

Lineage 2

Lineage 3

Lineage 4

Figure 3 Major WNV lineages Maximum-likelihood phylogenetic tree is based on complete genome sequences and Nearest-Neighbor-Interchange as heuristic search methodThe tree was constructed using MEGA 6 with 1000 bootstrap replications The tree was rooted usingKoutango and Usutu viruses

Enzootic Cycle

Transfusion andtransplantation

Epidemic

Epizootic

Fecal-oraltransmission

Vertical transmission

Figure 4 WNV transmission cycle enzootic amplification of WNV by birds and mosquitoes supplemented by bird-to-bird transmissionand transmission between cofeeding mosquitoes Vertical transmission by mosquitoes provides the mechanism of virus overwinteringHumans and horses are counted as incidental dead-end hosts Human-to-human transmission may come through blood transfusion organtransplantation and breast feeding and in utero

arboviruses such as dengue virus and yellow fever virusWNV can be transmitted by a variety of mosquitoes withdifferent host-feeding preferences with up to 45 species and 8genera reported positive in the US between 2004 and 2008[108] However not all mosquito species reported as WNV-positive are competent vectors of WNV and not all species

that are transmission-competent in the laboratory will play arole in natural transmission [109]

Mosquitoes that feed on both birds and mammals arereferred to as bridge vectors for WNV because they act asa ldquobridgerdquo between an infected reservoir (birds) and mam-malian incidental hosts which do not develop sufficiently


high viremia to support transmission to mosquitoes [110111] Ornithophilic mosquitoes play an important role inmaintaining and amplifying transmission among birds buttypically do not play a role in transmission to humans [109111] Mosquitoes of the genus Culex have been reportedas the most important bridge vectors in the United Stateswith Cx pipiens as the dominant bridge vector in thenortheastern north-central and mid-Atlantic United StatesCx quinquefasciatus in the south and southwest and Cxtarsalis in the west [110 112] Culex spp mosquitoes have alsobeen implicated in transmission in Europe Australia andSouth Africa [113ndash116] Mosquitoes of the genus Aedes thetransmission vector for related flaviviruses may also serveas important bridge vectors [108 109] While experimentaltransmission of WNV by ticks has been demonstrated a rolefor ticks in natural transmission and maintenance of WNVhas not been determined [117ndash121]

5 Epidemiology and Clinical Outcomes ofHuman Infections

Most human infections with WNV (sim80) are asymp-tomatic and symptomatic infections may vary from flu-likemalaise to serious neuroinvasive diseases for which there isno specific treatment Fewer than 1 of human infectionsprogress to severe disease for which the most frequentlyreported risk factors include advanced age immune suppres-sion and chronic medical conditions including but are notlimited to hypertension diabetes and chronic renal failure[122ndash131] In 2002 out of more than 4000 cases reported tothe CDC 150 cases were in patients of age 19 or younger Theyoungest fatality was a 19-year-old patient and the medianage among fatal cases was 78 years [132] In the outbreak of2003 at least 31 cases of WNV encephalitis and 79 cases ofWNV meningitis occurred among children and adolescentshowever there were no fatalities caused by WNV disease inchildren or adolescents [132]

Seroepidemiological studies suggested that one in fourto one in five (20ndash25) WNV-infected individuals developsmild illness [133 134] and one person in 150 (067) developsWNND [135] Subsequent epidemiological studies usingasymptomatic infection data obtained from nucleic acidtesting to screen blood donations combinedwith the reportedcases to the CDC concluded that one in 244 to one in 353infections will progress to WNND [123 136] These findingssuggested that more asymptomatic WNV infections couldbe identified when prospective studies focused on healthypopulations such as blood donors [123 136] A serosurveyfollowing lineage 2WNV infections in Greece in 2010 yieldedestimates of one in 124 to one in 141 infections leadingto WNND with approximately 18 of infected individualsshowing symptoms [137]

AmongWNNDpatients 50ndash71developWNencephali-tis 15ndash35 develop meningitis and 3ndash19 develop acuteflaccid paralysis [126 128 138ndash145] Severe cases have fatalityrates ranging from 3 to 19 in encephalitis cases [126 128130 139 140 142ndash144 146 147] Loeb et al reported thatphysical and mental impairment resolve in about a year but

patients with preexisting comorbid conditions take longerto recover [148] However other studies of patients infectedwith WNV have noted physical symptoms andor cognitivedeficits persisting over a year after infection inmore than halfof WNND cases [141 149] Persistence of WNV symptomsgt6 months was reported most often in patients withWNNDhypertension and diabetes [150] WNND has also beenreported as a risk factor for development of chronic kidneydisease in a long-term follow-up study ofWNVpatients [151]

Although fewer cases are available fromwhich to conducta detailed study it is thought that both the risk of illness andthe risk of neuroinvasive infection are lower from the WNVKunjin subtype (lineage 1b) which circulates in Australia[152] Until recently viruses in lineage 2 were not believedto cause WNND in humans However outbreaks of lineage2WNV strains in the past 10 years in Russia and Greece havecaused WNND and death with case fatality rates similar tothose observed previously for lineage 1 WNV [124 147 153]WNND caused by WNV lineage 2 in horses and humans inSouth Africa has also been reported [79 154ndash156]

6 WNV in Africa and the Middle East

West Nile virus was first observed in Africa in the West Niledistrict of Uganda 1937 [10] and thus had been known in theOld World for over 60 years before it crossed the AtlanticThough it was first isolated from a febrile human case WNVwas observed to cause relatively mild disease in humans andno deaths were reported from the early epidemics studied[10] While the introduction and progress of WNV throughthe New World could be studied as it occurred epidemicsof WNV were believed to have occurred throughout muchof Africa the Middle East and south Asia before clinicalWNV was observed in humans in those areas A 1939-1940serosurvey foundwidespread human seropositivity forWNVdetermined by comparison of neutralization titers for WNVSLEV and JEV in Uganda Sudan the current DemocraticRepublic of the Congo and Kenya with seropositivity over50 in some localities [157] Seropositivity was also foundin western Nigeria in samples collected in 1951 and 1955[158] In South Africa seropositivity in humans who had nottraveled monkeys domestic animals and juvenile birds wasdemonstrated in samples collected in 1954 [159] Thereforethe past presence of WNV had been demonstrated over awide geographic range in Africa before clinical infectionswere observed in most locations

Following its first isolation in 1937WNVwas not isolatedagain until 1950 During a serosurvey conducted of 251individuals mostly children living in Cairo isolates weregenerated from the serum of three children only one ofwhom had been diagnosed with a fever [160] The sameserosurvey noted that more than 70 of the study partici-pants aged 4 and above carried neutralizing and complement-fixing antibodies to WNV and that over 50 of infantscarried maternal antibodies against WNV indicating thatWNV infection was widespread among the population andthatmost individuals were infected as young children [160] Asubsequent serosurvey in northeastern Egypt demonstrated


widespread seropositivity of adults and children at multiplelocations in the Nile Valley excluding one coastal locationindicating that WNV was not only endemic in Egypt butfrequently transmitted [161] WNV was also isolated fromCulex spp mosquitoes in Egypt in 1952 [162]

The first known isolation of West Nile virus in Israelwas from a febrile child in 1951 as part of an outbreakthat occurred on an agricultural settlement near Haifa [2]Morbidity in children in this outbreak was substantiallyhigher than in adults and subsequent outbreaks in Israel in1952 and 1953 occurring primarily in adolescents and adultswere also identified as WNV on the basis of isolation ofthe virus from human cases and serology from human casesand chickens [2 6 7] However WNV is believed to havebeen present in Israel prior to these isolations because prioroutbreaks between 1942 and 1950 were observed to have beensimilar clinically and epidemiologically to the ones in 1951and 1952 [6] Illnesses in these cases were generally self-limiting with recovery slower in adults than children [2 6]WNV fever was described as a ldquobenign specific short-termfever occurring in epidemic formrdquo and was believed to causeonly mild neuroinvasive cases [7] The first fatalities dueto WNND were reported in a cluster of elderly patients in1957 however overall neurological involvement in WNVcases was considered unusual [4 10 11 16] In 2000 thefirst WNV outbreak in Israel since 1980 was reported with417 serologically confirmed cases and 35 deaths [16] Viralisolates from this outbreak were most closely related toisolates from the 1996 Romanian and 1999 Russian outbreaks[163 164] Since then Israel has experienced regular annualsummertime outbreaks of varying size similar to thoseobserved in the United States [126 165ndash167]

Human seropositivity for WNV in Turkey was docu-mented in the 1970s and again beginning in the mid-2000s[168ndash172] An outbreak of WNV occurred in Turkey in 2010-11 concurrent with other outbreaks in the Mediterraneanregion causing 47 cases including 40 WNND cases and 10fatalities [173]

Seropositivity for WNV was also reported in Iran in the1970s [174] A 2008-2009 survey of patients with fever andloss of consciousness identified 3 cases whichwere positive byRT-PCR and 6 more that were positive by IgG [175] A studyof horses conducted from 2008-2009 identified IgM-positiveanimals and seroprevalences up to 88 in some regions withthe highest activity in western and southern provinces [176]Serologic evidence for infection has also been found in Jordanand Lebanon although no human cases have been reportedfrom those countries [177ndash180]

WNV continued to circulate in northern and sub-Saharan Africa throughout the late 20th and early 21stcentury causing outbreaks in Algeria Morocco Tunisia theDemocratic Republic of the Congo and South Africa alongwith sporadic cases and seropositivity in humans andorhorses distributed throughout the continent [165 181ndash184]Active transmission has continued in northern Africa withoutbreaks reported in Morocco in 2010 and Tunisia in 2012and ongoing sporadic transmissions in Egypt and Algeria[165 183 185ndash189]

The regular pattern of infection in South Africa prior to1974 was sporadic relatively mild human infections and epi-zootics with epidemics in humans occurring in 1974 and 1984(reviewed in [8]) The relative nonpathogenicity of humanand equine infections in South Africa had been attributedto reduced pathogenicity of lineage 2 WNV strains howeverlater reports of WNND caused by lineage 2 WNV infectionsin South Africa suggested that the full clinical extent ofWNV infection in earlier epidemics may not have beenrecognized [79 156] In 2010 the first case of lineage 1 WNVoccurring in South Africa caused the death of a pregnantmare [190] Infections caused by lineage 2 inMadagascar havealso generally been considered mild to inapparent one fatalcase of WNND originated in Madagascar in 2011 althoughit was speculated that the patient had a deficient antibodyresponse [191]

Recent reports have indicated ongoing transmission inother regions of sub-Saharan Africa Eleven cases of acutefebrile illness were caused by WNV in Guinea in 2006 [192]A 2009 seroprevalence study in Ghana indicated that WNVis endemic with most WNV cases occurring in childhood[193] A fatality due to WNND was reported in Gabon in2009 [194] A study in Nigeria demonstrated that 25 oftested febrile patientsmany ofwhomwere infectedwithPlas-modium falciparum or Salmonella Typhi were seropositivefor WNV suggesting that WNV infection in this region maybe mistaken for these diagnoses or for other cocirculatingarboviruses [195] Seroconversion of sentinel chickens wasobserved in Senegal in 2009 [196] In eastern Africa humaninfections and mosquitoes positive for WNV lineage 2 werereported in Djibouti from 2010-2011 [197] Recent positivityfor WNV in Kenya has also been reported in ticks collectedfrom 2010ndash2012 and mosquitoes from 2007ndash2011 [121 198]

7 WNV in Southern and Eastern AsiaAustralia and Oceania

In the early 1950s and 1960s seropositivity for WNV wasdemonstrated throughout India and as far east as Myan-mar [199 200] Sporadic cases were documented in Indiathroughout the 1970sndash2000s [3] Most sequenced isolatesfrom India separate into a distinct lineage referred to aslineage 5 or lineage 1C although lineage 1A isolates havealso been reported [3 72 86 201] Although WNV hadpreviously been shown to cause neurological disease thefirst pediatric fatalities from WNND were reported in Indiawhere three children died of WNV encephalitis in 1981[5] Pediatric WNND cases have been frequently reportedin Indian WNV outbreaks in contrast to North Americanand European WNV outbreaks in which pediatric cases arerelatively infrequent [3 5 202ndash204]

Recent reports on WNV in India have included ongoingisolation and sequencing of both WNV lineages 1A and 5as well as cocirculation and possibly coinfection with JEV in2006 in areas of northeastern India where both WNV andJEV are endemic [86 201 202 204 205]The 2010 outbreak oflineage 1WNV inTamilNadu statewas associatedwith oculardisease an infrequently reported WNV complication [201]


The recent lineage 5 isolates reported from northeasternIndia were more neuroinvasive and pathogenic in mice thanIndian isolates from 1982 and earlier [86] Cases of WNNDhave also been reported from Pakistan along with humanseroprevalences ranging from 12 to 54 [206ndash209]

Isolations of WNV have been reported in Malaysia andCambodia and seropositivity for WNV was also notedin Myanmar Thailand and the Philippines [88 200 210ndash212] Lineage 2 WNV was sequenced from an acute febrilespecimen collected in 2004 in Indonesia [81] RecentlyWNVhas also been isolated from clinical specimens collected inNepal from 2009-2010 sequenced fragments of both isolatesshowed homology primarily to lineage 1 viruses but onefragment of each wasmore similar to lineage 2 than to lineage1 [213]

In China seropositivity for WNV was first reported inbirds from Yunnan province in 1988 [214 215] The firstconfirmed human cases of WNV in China were reportedin 2013 but occurred during a 2004 outbreak of fever andneurological disease in Xinjiang province in northwesternChina in which diagnosis was delayed due to antibody cross-reactivity with Japanese encephalitis virus [214] Seropositiv-ity for WNV in Shanghai was reported in 149 of cats and49 of dogs tested in 2010 as well as in captive resident birdsfrom 2009-2010 but no human cases have been reportedfrom southern or eastern China [216 217] In South Koreaantibody againstWNVwas detected in 51531 bird specimensin a 2009 study but no resident birds were seropositive [218]

Kunjin virus which was originally considered to be aclosely related virus but is now considered a subspecies ofWNV lineage I was first isolated in Australia in 1960 [219220] Symptoms of WNVKunjin in Australia are consid-ered relatively mild with infrequent WNND and no deathsreported [115 221] WNVKunjin has continued to causeintermittent cases of equine and human disease in Australiaprimarily in the northwest where it frequently cocircu-lates with the related flavivirus Murray Valley encephalitisvirus (MVEV) [221] In 2011 an outbreak of WNV (co-circulating with MVEV) in horses in southeastern Australiawas attributed to a strain of WNV designated WNVNSW2011which was closely related to Kunjin virus but carried twoamino acid changes previously associated with increasedvirulence in North AmericanWNVNY99 strains [222ndash224]These changes rendered WNVNSW2011 significantly moreneuroinvasive than previously observed Australian strainsHowever no human cases were reported from this outbreakand a serosurvey in Victoria showed little evidence of recenthumanWNV infection [225]

8 WNV in Europe

The presence of WNV was first discovered in Europe in1958 in Albania with detection of neutralizing antibodies inhuman sera [226 227] The first documented outbreak ofWNV occurred in southern France in 1962-1963 causingWNND in both humans and horses [1 9] Following thatoutbreak no further WNND cases in humans were reporteduntil 1985 although virus activity in the region has been

confirmed onmultiple occasionsThe virus was isolated frommosquitoes in Portugal and the Czech Republic migratingbirds in Slovakia and western Ukraine and ticks in Hungaryand the Moldavia region [227ndash231] WNV was also sporad-ically detected in serological surveys of humans migratorybirds and domestic animals in the countries throughoutsouthern and eastern Europe and the Mediterranean basinalthough the viruswas not considered a public health concernduring that time due to the absence of reported WNND[227 232 233]

However the situation has changed dramatically in thelast three decades with a series of symptomatic WNV out-breaks in several European countries Human WNND caseswere first observed in western Ukraine in 1985 followedby a period of relative silence and two major epidemics inRomania in 1996 and in Russia in 1999 [14 15 232] Duringthe outbreak in Romania 835 patients were hospitalized withneurological symptoms and 343 were confirmed to beWNV-positive The epidemic caused 17 deaths [15] The mortalityrate was even higher in Russia out of 826 patients whopresented with symptoms 183 tested positive in serologicalessays and 40 died of acute aseptic meningoencephalitis [14]

Other notable outbreaks with human cases from 2000ndash2009 include the reemergence of WNV in France in 2000ndash2003 Italy in 2008-2009 and Hungary in 2008 [232 234235] In France in 2000 WNND cases were confirmed in 76horses and 21 of them died interestingly the same regionof the country was affected as in the outbreak of 1962 [236]WNND cases described in 2003 involved horses and humans[237] A subsequent serologic survey in horses suggested thepossibility of persistent WNV circulation in the area [238]The 2008 outbreak in Italy was preceded by a 1998 eventwith 14 encephalitic equine cases and 4 asymptomatic cases inhumans a retrospective study revealed a 38 seroprevalencerate in horses in the region [239 240] In 2008-2009 bothequine and human WNND cases were reported [241] InHungary the sudden spread of the virus in 2008 caused 12equine and 22 human neuroinvasive cases [234] Followingthe large outbreak in 1999 Russia experienced annual sum-mer transmissions with sporadic outbreaks primarily in thesouth [242] The three most affected regions were AstrakhanRostov and Volgograd provinces with outbreaks in 20072010 and 2012 although recently the range of the virus hasapparently expanded with cases reported further north- andeastward in several provinces including southern parts ofSiberia [166]

With the outbreaks becoming more frequent and spo-radic cases surfacing all over Europe enhanced surveillanceprograms were established in many European countries[232 243] One such program was instrumental in promptlyidentifying WNV cases during the largest recorded out-break in Italy in 2012 where simultaneous circulation ofboth WNV lineage 1 and lineage 2 was documented [244ndash247] From 2010ndash2013 human WNV cases were reported inAustria Bosnia and Herzegovina Croatia Greece HungaryItaly Kosovo the Former Yugoslav Republic of MacedoniaMontenegro the Russian Federation Serbia Spain andUkraine [165 248ndash253] Greece and Russia experienced highWNV activity each year from 2010ndash2013 and 302 cases were


reported from Serbia in 2013 [165 166] Additionally thepresence of WNV was confirmed in the Czech RepublicPortugal and other countries where it had not previouslybeen identified with most of the reports suggesting seasonalintroduction by multiple routes and continuous low-levelWNV circulation in Europe [254 255]

Notably prior to 2008 lineage 1 viruses were responsiblefor severe WNND cases in humans in Europe and lineage2 viruses were only reported in sub-Saharan Africa andMadagascar until 2004 However the cases in Hungary werecaused by lineage 2 WNV with subsequent spread intoAustria Italy Russia Greece Serbia and Croatia [85 248255ndash260] The strain isolated from the 2010 Greek outbreakWNVNea-Santa-Greece 2010 was shown to carry amutationpreviously associated with increased virulence in corvids inlineage 1 WNV strains [261 262]

Countries with established surveillance programs and noreported clinical cases so far include the UK Germany andSwitzerland [263ndash265] One serologic study in the UK iden-tified WNV-seropositive wild birds although subsequentstudies have not found evidence of WNV circulation in birds[266ndash269] In Germany and Poland seroprevalence in birdswas relatively low [264 270]

9 WNV in the United States

WNV infection is a major public health concern in theUnited States where the virus has become endemic causingrecurring outbreaks for 14 consecutive years The initialoutbreak in the US resulted in 62 reported cases including59 WNND cases and 7 deaths however estimates based onserosurveillance suggest that 26 of the population nearthe outbreak epicenter in New York City was affected inthat outbreak [133] The WNV strain associated with theUS outbreak designated WNV NY99 was a lineage 1 strainclosely related to an isolate from the outbreak in Israel in1998 and both the US and Israeli strains were related to aTunisian isolate from 1997 [70 71 77 271] By the summer of2000 the virus had also caused human disease in the states ofNew Jersey and Connecticut with a total of 21 cases reportedincluding 19 WNND cases that resulted in 2 deaths [272]

In contrast to the historically observed pattern of out-breaks in Europe and Africa between the 50s and the 90s inwhich epidemics were followed by years of inactivity WNVcontinued to spread in the US following its introduction Inthe summer of 2001 the virus was found in 10 states with66 total reported cases (64 WNND) and 9 deaths In 200240 states reported a total of 4156 WNV human cases tothe CDC with 709 (2946) classified as WNND resultingin 284 fatalities Possibly due to increased awareness in themedical community through an outreach program by theHHS in 2003 the total number of reported cases increased42 to 9862 however the number of WNND cases declinedto 2866 which represented 29 of reported cases By 2004WNVhad been detected in all of the contiguous 48 states andwas considered endemic Another large outbreak occurredin 2006 with 177 deaths and 1495 WNND cases out of atotal of 4260 cases Coincidentwith the 2002-2003 outbreaks

a new viral genotype known as WN02 replaced the originalviral genotype NY99 the new genotype was observed todisseminatemore efficiently inNorthAmericanCulex pipiensand Culex tarsalismosquitoes than the NY99 genotype [273ndash276]

The intensity of WNV activity in the US was very highbetween 2002 and 2007 with over 1000 WNND cases peryear A decline in the number of cases began in 2008 andcomparatively low activity continued through 2011 when only712 totalWNVcases were reported In 2012 however anotherlarge outbreak of WNV occurred in the US causing 2873WNND cases and the most deaths [277] ever reported in asingleWNVseasonActivity in theUS in 2013wasmoderatewith 1267 WNND cases and 119 deaths in 2013 reported asof May 9 2014 From 1999ndash2013 there have been a total of39557 reported cases of WNV in the US of which 17381were WNND resulting in 1667 deaths an average of 1111deathsyear [278] (Figure 5)

Based on epidemiological estimates that for each caseof WNND there are 150 to 350 human infections 26 to61 million people in the United States have been infectedwith WNV over the past 14 years Through 2010 it wasestimated that 11 of the US population had been infectedby WNV with the highest incidence in the state of SouthDakota (133) [123 279] Because most WNV infections areasymptomatic or mild many human infections may not berecognized and there may be significant underreporting ofmilder symptomatic cases [133 279]

10 WNV in Other Parts of North America

In 2001 WNV was first detected in 128 dead birds and 9mosquito pools in Ontario Canada [280] Human cases inCanada were first reported in 2002 with 394 in Ontarioand 20 in Quebec [281] In 2003 WNV spread westwardto Manitoba Saskatchewan and Alberta but did not reachBritish Columbia until 2009 [281 282] Since 2002 Canadahas experienced annual summer outbreaks similar to thosein the United States with the largest outbreaks occurring in2003 (1481 cases) 2007 (2215 cases) and 2012 (428 cases)[281 283] (Figure 6)

The first WNV activity in the Caribbean was a humanWNVencephalitis case reported at the end of 2001 in theCay-man Islands [284]MostCaribbeanWNVactivity for the nextfew yearswas limited to observations of seropositivity in birdsand horses In 2002WNVactivity was observed inmigratoryand resident birds in Jamaica and the Dominican Republicand in horses inGuadeloupe An avian serosurvey in JamaicaPuerto Rico and Mexico in spring 2002 reported detectionof specific neutralizing antibodies for WNV in 11 residentspecies from Jamaica only [285] In the Dominican Republica seroepidemiological study performed in birds sampled inNovember 2002 on the eastern side of the country showedanti-WNV antibodies in 15 (533) of resident birds [286] By2003 WNV seropositivity had also been detected in residentbirds on the northwestern side of the Dominican Republic[277] A serosurvey of 360 healthy horses in Guadeloupeshowed an increase in prevalence of IgG antibodies to WNV


Year

Case

s

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

0100

2000

4000

6000

8000

10000

12000

Neuroinvasive casesNon-neuroinvasive cases

(a)

Dea

ths

0

50

100

150

200

250

300

350

Year

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

(b)

Figure 5 (a) Neuroinvasive and nonneuroinvasive cases of WNV in the United States reported to the CDC 1999ndash2013 (b) Deaths fromWNV infection in the United States reported to the CDC 1999ndash2013

Clin

ical

case

s

0

500

1000

1500

2000

2500

Year

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

Figure 6 Total clinicalWNVcases inCanada reported to the PublicHealth Agency of Canada 2002ndash2013

from 88 in June 2002 to 50 in January 2003 indicatinga high incidence of WNV infections in horses within that 6-month period [287]

The second Caribbean human WNV encephalitis caseoccurred in the Bahamas in July 2003 [288] WNV wasdetected in Trinidad in October 2004 in a serosurvey of60 horses and 40 birds with reported seropositivity of 3and 5 respectively [288 289] In CubaWNV infection wasconfirmed by serologic assays in 4 asymptomatic horses and3 humans with encephalitis in 2003 and 2004 [290] A 2004serosurvey of over 1900 resident and migrant birds in PuertoRico and Cuba found 10 WNV-positive birds (9 migrant 1resident) in Puerto Rico and 3 birds (1 migrant 2 resident)in Cuba [291] Three seropositive horses were observed in2004-2005 in Puerto Rico followed by detection of WNV in

three blood donors in 2007 [292] A 2007 isolate from PuertoRico carried themutation V159A in the envelope gene whichis characteristic of the WN02 genotype which replaced theoriginal NY99 genotype in the US [293] Two further WNVhuman cases were detected in Haiti during surveillance offebrile patients following Hurricane Jeanne in 2004 [294]

In 2002 WNV appeared in Mexico with reports ofencephalitis-like illness in horses in different areas concur-rent with reports of WNV encephalitis outbreaks in horsesalong the Texas border in the states of Coahuila Tamaulipasand Chihuahua [295] Mexico has reported low numbersof cases in humans horses and birds primarily from thenorthern border with the United States The first confirmedautochthonous human case of WNV in Mexico was reportedin 2004 [296] A fatal human case in 2009 was reported in a40-year-old man who had mild symptoms for several weeksthen progressed to neurological disease coma and death[297]

A surveillance study inMexico found relatively low levelsof WNV transmission and disease which were attributedto multiple factors including the interactions of amplifyinghosts vectors and circulating virus strains in combina-tion with climate habitat and circulation of interferingflaviviruses [298] A Mexican isolate from 2003 was shownto have reduced pathogenicity for mice crows and sparrowswhich may also have contributed to a reduced presence ofWNV in Mexico [299 300]

In El Salvador an investigation of outbreaks from 2003revealed that 25 (1873) of equine specimens tested hadantibodies toWNV and were confirmed by plaque reductionneutralization tests (PRNT) [301] In October 2003 WNVwas also identified in horses in Belize [289]

A 2003-2004 serosurvey conducted at multiple locationsin Guatemala detected 9 horses positive for WNV [302]Seropositivity in horses in Costa Rica was also reported from


a 2004 serosurvey [303] The only human case of WNV fromNicaragua was reported in a Spanishmissionary who becameill in the summer of 2006 while living in Nicaragua and wassubsequently transferred to Spain for treatment where hewasdiagnosed [18]

11 WNV in South America

The first detection of WNV in South America was in anautumn 2004 epidemiological survey of horses which had notbeen vaccinated againstWNVor traveled outside of Cordobaand Sucre in the Caribbean region of Colombia [304 305]

WNV was next reported in northern Argentina whereWNV was isolated from the brains of 3 horses that diedfrom encephalitis in February 2006 [306] A later reportshowed that resident birds in Cordoba Chaco and Tucumanprovinces had antibodies to WNV as early as January 2005and seroconversions were observed in three birds betweenJanuary and March 2005 [307] In December 2006 healthauthorities reported 4 human cases 1 case in the city ofMarcos Juarez in Cordoba province and 3 additional cases inChaco province [17]The case in Cordoba occurred inMarchof that year in a 58-year-oldmanwhohadnot traveled outsidethe country in recent years suggesting that the disease wascontracted locally [17]

In 2006 WNV was also reported in birds and horsesin Venezuela in a seroepidemiological study with PRNTconfirmation [308] WNV was detected in Brazil in a studyperformed on samples collected in 2009 from mosquitoeshorses and caimans from the Pantanal region of Central-West Brazil in which a total of 5 out of 168 horse spec-imens tested positive for WNV using a flavivirus-specificepitope-blocking enzyme-linked immunosorbent assay withconfirmation of reactive specimens by PRNT [309] Furtherstudies performed with specimens from the Pantanal regionwhere WNV cocirculates with multiple other flaviviruseshave foundWNV seropositivity confirmed by PRNT in horseand chicken samples collected in 2009 and later [310ndash312]WNV seropositivity was also reported in an equine samplecollected in 2009 in Paraiba state in northeastern Brazil [313]However WNV has not yet been associated with human orequine illness in Brazil [314]

A study conducted on a subset of 20880 samplesfrom individuals with acute febrile illnesses from BoliviaParaguay Ecuador and Peru from 2000ndash2007 identified atleast one patient with PRNT-confirmed seropositivity forWNV however no virus was isolated and the number andlocation of WNV-positive patients were not given [315] A2011 serosurvey of horses in Bolivia found PRNT-confirmedseropositivity for WNV although no horses were IgM-positive indicating thatWNVhad circulated in the area priorto 2011 [316]

Interestingly sequences obtained from Colombian viralisolates in 2008 were most closely related to 2001 LouisianaUS sequences of the NY99 genotype suggesting that theWN02 genotype which replaced NY99 in the US had notprogressed southward over that time period [317]

12 Conclusion

Since its discovery in 1937 West Nile virus has spread beyondits original known geographic range and caused humandisease on every continent except Antarctica It is now themost widespread cause of arboviral neurological disease inthe world With no vaccine available to date and limitedtreatment options transmission via organ donation andblood transfusion also poses a risk

While expansion of WNV into Central America SouthAmerica and the Caribbean has been marked by relativelyfew humanWNND cases and recovery of attenuated virusescharacterization of strains isolated from recent outbreaksin Greece Australia and India shows increased virulencein tissue culture andor animal models [86 222 262 300]However none of the observed changes has been directlycorrelated to virulence in human infections

Recent large outbreaks of human WNND in Europeand North America as well as ongoing transmission inthe Middle East Africa and Asia illustrate the need forcontinued surveillance and preventative measures The riskfor transmission and outbreaks remains high in the manyparts of the world with suitable mosquito vectors

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] G Balanca N Gaidet G Savini et al ldquoLow West Nile viruscirculation in wild birds in an area of recurring outbreaks inSouthern Francerdquo Vector-Borne and Zoonotic Diseases vol 9no 6 pp 737ndash741 2009

[2] H Bernkopf S Levine and R Nerson ldquoIsolation of West Nilevirus in IsraelrdquoThe Journal of Infectious Diseases vol 93 no 3pp 207ndash218 1953

[3] V P Bondre R S Jadi A C Mishra P N Yergolkar and V AArankalle ldquoWest Nile virus isolates from India evidence for adistinct genetic lineagerdquo Journal of General Virology vol 88 no3 pp 875ndash884 2007

[4] E Flatau D Kohn O Daher and N Varsano ldquoWest Nile feverencephalitisrdquo Israel Journal ofMedical Sciences vol 17 no 11 pp1057ndash1059 1981

[5] S George M Gourie-Devi J A Rao S R Prasad and K MPavri ldquoIsolation of West Nile virus from the brains of childrenwho had died of encephalitisrdquo Bulletin of the World HealthOrganization vol 62 no 6 pp 879ndash882 1984

[6] N Goldblum V V Sterk and B Paderski ldquoWest nile feverThe clinical features op tue disease and the isolation of westnile virus from the blood of nine human casesrdquo The AmericanJournal of Epidemiology vol 59 no 1 pp 89ndash103 1954

[7] K Marberg N Goldblum V V Sterk W Jasinska-klingbergand M A Klingberg ldquoThe natural history of west nile feverI Clinical observations during an epidemic in Israelrdquo TheAmerican Journal of Epidemiology vol 64 no 3 pp 259ndash2691956


[8] P G Jupp ldquoThe ecology of West Nile virus in South Africa andthe occurrence of outbreaks in humansrdquoAnnals of the New YorkAcademy of Sciences vol 951 pp 143ndash152 2001

[9] BMurgue SMurri H Triki V Deubel andH G Zeller ldquoWestnile in the mediterranean basin 1950ndash2000rdquo Annals of the NewYork Academy of Sciences vol 951 pp 117ndash126 2001

[10] K C Smithburn T P Hughes A W Burke and J H Hall ldquoAneurotropic virus isolated from the blood of a native ofUgandardquoTheAmerican Journal of Tropical Medicine and Hygiene vol 20pp 471ndash472 1940

[11] I SpiglandW Jasinska-Klingberg E Hofshi andNGoldblumldquoClinical and laboratory observations in an outbreak of WestNile fever in Israel in 1957rdquo Harefuah vol 54 no 11 pp 275ndash280 1958

[12] W Pruzanski and R Altman ldquoEncephalitis due to West Nilefever virusrdquoWorld neurology vol 3 pp 524ndash528 1962

[13] D E Carey F M Rodrigues R M Myers and J K WebbldquoArthropod-borne viral infections in children in Vellore SouthIndia with particular reference to dengue and West Nilevirusesrdquo Indian Pediatrics vol 5 no 7 pp 285ndash296 1968

[14] A E Platonov G A Shipulin O Y Shipulina et al ldquoOutbreakof West Nile virus infection Volgograd Region Russia 1999rdquoEmerging Infectious Diseases vol 7 no 1 pp 128ndash132 2001

[15] T F Tsai F Popovici C Cernescu G L Campbell and NI Nedelcu ldquoWest Nile encephalitis epidemic in SoutheasternRomaniardquoThe Lancet vol 352 no 9130 pp 767ndash771 1998

[16] M Weinberger S D Pitlik D Gandacu et al ldquoWest Nilefever outbreak Israel 2000 epidemiologic aspectsrdquo EmergingInfectious Diseases vol 7 no 4 pp 686ndash691 2001

[17] ISID ldquoWest Nile Virus Update 2006mdashWestern Hemisphere(23) Argentina First Caserdquo 2006 httpwwwpromedmailorgdirectphpid=200612283642

[18] B M Maillo R Lopez-Velez F Norman F de Ory M PSanchez-Seco and C G Fedele ldquoImportation of West Nilevirus infection from Nicaragua to Spainrdquo Emerging InfectiousDiseases vol 14 no 7 pp 1171ndash1173 2008

[19] C H Calisher N Karabatsos J M Dalrymple et al ldquoAntigenicrelationships between flaviviruses as determined by cross-neutralization tests with polyclonal antiserardquo Journal of GeneralVirology vol 70 no 1 pp 37ndash43 1989

[20] A T de Madrid and J S Porterfield ldquoThe flaviviruses (groupB arboviruses) a cross neutralization studyrdquo Journal of GeneralVirology vol 23 no 1 pp 91ndash96 1974

[21] E Castle T Nowak U Leidner and G Wengler ldquoSequenceanalysis of the viral core protein and the membrane-associatedproteins V1 and NV2 of the flavivirus west nile virus and of thegenome sequence for these proteinsrdquo Virology vol 145 no 2pp 227ndash236 1985

[22] E Castle U Leidner T Nowak G Wengler and G WenglerldquoPrimary structure of the West Nile flavivirus genome regioncoding for all nonstructural proteinsrdquo Virology vol 149 no 1pp 10ndash26 1986

[23] G Coia M D Parker G Speight M E Byrne and E GWestaway ldquoNucleotide and complete amino acid sequences ofKunjin virus Definitive gene order and characteristics of thevirus-specified proteinsrdquo Journal of General Virology vol 69 no1 pp 1ndash21 1988

[24] G Speight G Coia M D Parker and E G WestawayldquoGenemapping and positive identification of the non-structuralproteins NS2A NS2B NS3 NS4B and NS5 of the flavivirusKunjin and their cleavage sitesrdquo Journal of General Virology vol69 no 1 pp 23ndash34 1988

[25] G Wengler E Castle U Leidner T Nowak and G WenglerldquoSequence analysis of themembrane protein V3 of the flavivirusWest Nile virus and of its generdquoVirology vol 147 no 2 pp 264ndash274 1985

[26] M A Brinton A V Fernandez and J H Dispoto ldquoThe31015840-nucleotides of flavivirus genomic RNA form a conservedsecondary structurerdquo Virology vol 153 no 1 pp 113ndash121 1986

[27] G Wengler and E Castle ldquoAnalysis of structural propertieswhich possibly are characteristic for the 31015840-terminal sequenceof the genome RNA of flavivirusesrdquo Journal of General Virologyvol 67 no 6 pp 1183ndash1188 1986

[28] T Nowak P M Farber G Wengler and G Wengler ldquoAnalysesof the terminal sequences of West Nile virus structural proteinsand of the in vitro translation of these proteins allow theproposal of a complete scheme of the proteolytic cleavagesinvolved in their synthesisrdquo Virology vol 169 no 2 pp 365ndash376 1989

[29] F X Heinz and K Stiasny ldquoFlaviviruses and their antigenicstructurerdquo Journal of Clinical Virology vol 55 no 4 pp 289ndash295 2012

[30] A A Khromykh and E G Westaway ldquoRNA binding propertiesof core protein of the flavivirus KunjinrdquoArchives of Virology vol141 no 3-4 pp 685ndash699 1996

[31] L Markoff B Falgout and A Chang ldquoA conserved internalhydrophobic domainmediates the stablemembrane integrationof the dengue virus capsid proteinrdquo Virology vol 233 no 1 pp105ndash117 1997

[32] Y Zhang J Corver P R Chipman et al ldquoStructures ofimmature flavivirus particlesrdquo The EMBO Journal vol 22 no11 pp 2604ndash2613 2003

[33] F Guirakhoo F X Heinz C W Mandl H Holzmann and CKunz ldquoFusion activity of flaviviruses comparison ofmature andimmature (prM-containing) tick-borne encephalitis virionsrdquoJournal of General Virology vol 72 no 6 pp 1323ndash1329 1991

[34] F X Heinz K Stiasny G Puschner-Auer et al ldquoStructuralchanges and functional control of the tick-borne encephalitisvirus glycoprotein E by the heterodimeric association withprotein prMrdquo Virology vol 198 no 2 pp 109ndash117 1994

[35] K Stadler S L Allison J Schalich and F X Heinz ldquoProteolyticactivation of tick-borne encephalitis virus by furinrdquo Journal ofVirology vol 71 no 11 pp 8475ndash8481 1997

[36] Y Zhang B Kaufmann P R Chipman R J Kuhn and M GRossmann ldquoStructure of immature West Nile virusrdquo Journal ofVirology vol 81 no 11 pp 6141ndash6145 2007

[37] J Junjhon T J Edwards U Utaipat et al ldquoInfluence of pr-M cleavage on the heterogeneity of extracellular dengue virusparticlesrdquo Journal of Virology vol 84 no 16 pp 8253ndash83582010

[38] B Kaufmann and M G Rossmann ldquoMolecular mechanismsinvolved in the early steps of flavivirus cell entryrdquoMicrobes andInfection vol 13 no 1 pp 1ndash9 2011

[39] J M Smit B Moesker I Rodenhuis-Zybert and J WilschutldquoFlavivirus cell entry and membrane fusionrdquo Viruses vol 3 no2 pp 160ndash171 2011

[40] K Stiasny and F X Heinz ldquoFlavivirus membrane fusionrdquoJournal of General Virology vol 87 no 10 pp 2755ndash2766 2006

[41] A A Khromykh P L Sedlak and E G Westaway ldquotrans-Complementation analysis of the flavivirus Kunjin ns5 genereveals an essential role for translation of its N-terminal half inRNA replicationrdquo Journal of Virology vol 73 no 11 pp 9247ndash9255 1999


[42] B D Lindenbach and C M Rice ldquotrans-complementation ofyellow fever virus NS1 reveals a role in early RNA replicationrdquoJournal of Virology vol 71 no 12 pp 9608ndash9617 1997

[43] J M Mackenzie M K Jones and P R Young ldquoImmunolo-calization of the dengue virus nonstructural glycoprotein NS1suggests a role in viral RNA replicationrdquo Virology vol 220 no1 pp 232ndash240 1996

[44] P Borowski A O Niebuhr M Mueller et al ldquoPurification andcharacterization of West Nile virus nucleoside triphosphatase(NTPase)helicase evidence for dissociation of the NTPase andhelicase activities of the enzymerdquo Journal of Virology vol 75 pp3220ndash3229 2001

[45] T J Chambers A Nestorowicz S M Amberg and C M RiceldquoMutagenesis of the yellow fever virus NS2B protein effects onproteolytic processingNS2B-NS3 complex formation and viralreplicationrdquo Journal of Virology vol 67 no 11 pp 6797ndash68071993

[46] B Falgout R H Miller and C-J Lai ldquoDeletion analysis ofdengue virus type 4 nonstructural protein NS2B identificationof a domain required for NS2B-NS3 protease activityrdquo Journalof Virology vol 67 no 4 pp 2034ndash2042 1993

[47] A E Gorbalenya E V Koonin A P Donchenko and V MBlinov ldquoTwo related superfamilies of putative helicases involvedin replication recombination repair and expression of DNAand RNA genomesrdquo Nucleic Acids Research vol 17 no 12 pp4713ndash4730 1989

[48] S A Shiryaev A V Chernov A E Aleshin T N Shiryaevaand A Y Strongin ldquoNS4A regulates the ATPase activity of theNS3 helicase a novel cofactor role of the non-structural proteinNS4A from West Nile virusrdquo Journal of General Virology vol90 no 9 pp 2081ndash2085 2009

[49] G Wengler G Czaya P M Farber and J H Hegemann ldquoInvitro synthesis of West Nile virus proteins indicates that theamino-terminal segment of the NS3 protein contains the activecentre of the protease which cleaves the viral polyprotein aftermultiple basic amino acidsrdquo Journal of General Virology vol 72no 4 pp 851ndash858 1991

[50] A A Khromykh M T Kenney and E G Westaway ldquotrans-Complementation of flavivirus RNA polymerase gene NS5 byusing Kunjin virus replicon-expressing BHK cellsrdquo Journal ofVirology vol 72 no 9 pp 7270ndash7279 1998

[51] E V Koonin ldquoComputer-assisted identification of a putativemethyltransferase domain in NS5 protein of flaviviruses and 1205822protein of reovirusrdquo Journal of General Virology vol 74 no 4pp 733ndash740 1993

[52] D Ray A Shah M Tilgner et al ldquoWest Nile virus 51015840-capstructure is formed by sequential guanine N-7 and ribose 21015840-Omethylations by nonstructural protein 5rdquo Journal of Virologyvol 80 no 17 pp 8362ndash8370 2006

[53] S Steffens H-JThiel and S-E Behrens ldquoThe RNA-dependentRNA polymerases of different members of the family Fla-viviridae exhibit similar properties in vitrordquo Journal of GeneralVirology vol 80 no 10 pp 2583ndash2590 1999

[54] M A Brinton ldquoThe molecular biology of West Nile virus anew invader of the Western hemisphererdquo Annual Review ofMicrobiology vol 56 pp 371ndash402 2002

[55] J Y LeungG P PijlmanNKondratieva JHyde JMMacken-zie and A A Khromykh ldquoRole of nonstructural protein NS2Ain flavivirus assemblyrdquo Journal of Virology vol 82 no 10 pp4731ndash4741 2008

[56] W J Liu H B Chen and A A Khromykh ldquoMolecular andfunctional analyses of Kunjin virus infectious cDNA clones

demonstrate the essential roles for NS2A in virus assemblyand for a nonconservative residue in NS3 in RNA replicationrdquoJournal of Virology vol 77 no 14 pp 7804ndash7813 2003

[57] S Youn R L Ambrose J M MacKenzie and M S DiamondldquoNon-structural protein-1 is required for West Nile virus repli-cation complex formation and viral RNA synthesisrdquo VirologyJournal vol 10 article 339 2013

[58] P Avirutnan A Fuchs R E Hauhart et al ldquoAntagonism of thecomplement component C4 by flavivirus nonstructural proteinNS1rdquo Journal of Experimental Medicine vol 207 no 4 pp 793ndash806 2010

[59] P Avirutnan R E Hauhart P Somnuke AM BlomM S Dia-mond and J P Atkinson ldquoBinding of flavivirus nonstructuralprotein NS1 to C4b binding protein modulates complementactivationrdquo Journal of Immunology vol 187 no 1 pp 424ndash4332011

[60] K M Chung M K Liszewski G Nybakken et al ldquoWest Nilevirus nonstructural protein NS1 inhibits complement activationby binding the regulatory protein factor Hrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 103 no 50 pp 19111ndash19116 2006

[61] M C Kyung B S Thompson D H Fremont and M SDiamond ldquoAntibody recognition of cell surface-associated NS1triggers Fc-120574 receptor-mediated phagocytosis and clearance ofWest Nile virus-infected cellsrdquo Journal of Virology vol 81 no 17pp 9551ndash9555 2007

[62] M Laurent-Rolle E F Boer K J Lubick et al ldquoTheNS5 proteinof the virulentWestNile virusNY99 strain is a potent antagonistof type I interferon-mediated JAK-STAT signalingrdquo Journal ofVirology vol 84 no 7 pp 3503ndash3515 2010

[63] J L Wen B C Hua J W Xiang H Huang and A AKhromykh ldquoAnalysis of adaptive mutations in Kunjin virusreplicon RNA reveals a novel role for the flavivirus nonstruc-tural protein NS2A in inhibition of beta interferon promoter-driven transcriptionrdquo Journal of Virology vol 78 no 22 pp12225ndash12235 2004

[64] W J Liu X J Wang V V Mokhonov P-Y Shi R Randall andA A Khromykh ldquoInhibition of interferon signaling by the NewYork 99 strain and Kunjin subtype of West Nile virus involvesblockage of STAT1 and STAT2 activation by nonstructuralproteinsrdquo Journal of Virology vol 79 no 3 pp 1934ndash1942 2005

[65] E B Melian J H Edmonds T K Nagasaki E Hinzman NFloden and A A Khromykh ldquoWest Nile virus NS2A proteinfacilitates virus-induced apoptosis independently of interferonresponserdquo Journal of General Virology vol 94 no 2 pp 308ndash313 2013

[66] J L Munoz-Jordan M Laurent-Rolle J Ashour et al ldquoInhibi-tion of alphabeta interferon signaling by the NS4B protein offlavivirusesrdquo Journal of Virology vol 79 no 13 pp 8004ndash80132005

[67] J R Wilson P F De Sessions M A Leon and F ScholleldquoWest Nile virus nonstructural protein 1 inhibits TLR3 signaltransductionrdquo Journal of Virology vol 82 no 17 pp 8262ndash82712008

[68] T Bakonyi Z Hubalek I Rudolf and N Nowotny ldquoNovelflavivirus or new lineage of West Nile virus Central EuroperdquoEmerging Infectious Diseases vol 11 no 2 pp 225ndash231 2005

[69] F-X Berthet H G Zeller M-T Drouet J Rauzier J-PDigoutte and V Deubel ldquoExtensive nucleotide changes anddeletions within the envelope glycoprotein genes of Euro-African West Nile virusesrdquo Journal of General Virology vol 78no 9 pp 2293ndash2297 1997


[70] X-Y Jia T Briese I Jordan et al ldquoGenetic analysis ofWest NileNewYork 1999 encephalitis virusrdquoTheLancet vol 354 no 9194pp 1971ndash1972 1999

[71] R S Lanciotti G D Ebel V Deubel et al ldquoComplete genomesequences and phylogenetic analysis of West Nile virus strainsisolated from the United States Europe and the Middle EastrdquoVirology vol 298 no 1 pp 96ndash105 2002

[72] F J May C T Davis R B Tesh and A D T Barrett ldquoPhy-logeography of West Nile virus from the cradle of evolutionin Africa to Eurasia Australia and the Americasrdquo Journal ofVirology vol 85 no 6 pp 2964ndash2974 2011

[73] J H Scherret M Poidinger J S Mackenzie et al ldquoTherelationships between West Nile and Kunjin virusesrdquo EmergingInfectious Diseases vol 7 no 4 pp 697ndash705 2001

[74] E M Botha W Markotter M Wolfaardt et al ldquoGeneticdeterminants of virulence in pathogenic lineage 2 West Nilevirus strainsrdquo Emerging Infectious Diseases vol 14 no 2 pp222ndash230 2008

[75] A Vazquez M P Sanchez-Seco S Ruiz et al ldquoPutative newlineage of West Nile virus Spainrdquo Emerging Infectious Diseasesvol 16 no 3 pp 549ndash552 2010

[76] R GMcLean S R Ubico D Bourne andN Komar ldquoWestNilevirus in livestock and wildliferdquo Current Topics in Microbiologyand Immunology vol 267 pp 271ndash308 2002

[77] L R Petersen and J T Roehrig ldquoWest Nile virus a reemergingglobal pathogenrdquo Emerging Infectious Diseases vol 7 no 4 pp611ndash614 2001

[78] G Zehender E Ebranati F Bernini et al ldquoPhylogeographyand epidemiological history of West Nile virus genotype 1a inEurope and the Mediterranean basinrdquo Infection Genetics andEvolution vol 11 no 3 pp 646ndash653 2011

[79] F J Burt A A Grobbelaar P A Leman F S Anthony GV F Gibson and R Swanepoel ldquoPhylogenetic relationships ofSouthern African West Nile virus isolatesrdquo Emerging InfectiousDiseases vol 8 no 8 pp 820ndash826 2002

[80] K Erdelyi K Ursu E Ferenczi et al ldquoClinical and pathologicfeatures of lineage 2 West Nile virus infections in birds of preyin Hungaryrdquo Vector-Borne and Zoonotic Diseases vol 7 no 2pp 181ndash188 2007

[81] K S A Myint H Kosasih I M Artika et al ldquoShort reportwest nile virus documented in Indonesia from acute febrileillness specimensrdquo The American Journal of Tropical Medicineand Hygiene vol 90 no 2 pp 260ndash262 2014

[82] M Ciccozzi S Peletto E Cella et al ldquoEpidemiological historyand phylogeography of West Nile virus lineage 2rdquo InfectionGenetics and Evolution vol 17 pp 46ndash50 2013

[83] M T Aliota S A Jones A P Dupuis II A T Ciota Z Hubalekand L D Kramer ldquoCharacterization of Rabensburg virus aflavivirus closely related to West Nile virus of the Japaneseencephalitis antigenic grouprdquo PLoS ONE vol 7 no 6 ArticleID e39387 2012

[84] D K Lvov A M Butenko V L Gromashevsky et al ldquoWestNile virus and other zoonotic viruses in Russia examples ofemerging-reemerging situationsrdquo Archives of Virology Supple-ment no 18 pp 85ndash96 2004

[85] A E Platonov L S Karanrsquo T A Shopenskaia et al ldquoGenotypingof West Nile fever virus strains circulating in southern Russiaas an epidemiological investigation method principles andresultsrdquoZhurnalMikrobiologii Epidemiologii i Immunobiologiino 2 pp 29ndash37 2011

[86] P Chowdhury S A Khan P Dutta R Topno and J MahantaldquoCharacterization of West Nile virus (WNV) isolates fromAssam India insights into the circulating WNV in North-eastern Indiardquo Comparative Immunology Microbiology andInfectious Diseases vol 37 no 1 pp 39ndash47 2014

[87] G Fall M Diallo C Loucoubar O Faye and A A SallldquoVector competence of Culex neavei andCulex quinquefasciatus(Diptera Culicidae) from Senegal for lineages 1 2 Koutangoand a putative new lineage ofWest Nile virusrdquoAmerican Journalof Tropical Medicine and Hygiene vol 90 no 4 pp 747ndash7542014

[88] J S MacKenzie and D T Williams ldquoThe zoonotic flavivirusesof Southern South-Eastern and Eastern Asia and Australasiathe potential for emergent virusesrdquo Zoonoses and Public Healthvol 56 no 6-7 pp 338ndash356 2009

[89] K M Van Der Meulen M B Pensaert and H J NauwynckldquoWest Nile virus in the vertebrate worldrdquo Archives of Virologyvol 150 no 4 pp 637ndash657 2005

[90] N Komar S Langevin S Hinten et al ldquoExperimental infectionof North American birds with the New York 1999 strain ofWestNile virusrdquo Emerging Infectious Diseases vol 9 no 3 pp 311ndash322 2003

[91] A M Kilpatrick P Daszak M J Jones P P Marra and LD Kramer ldquoHost heterogeneity dominates West Nile virustransmissionrdquo Proceedings of the Royal Society B BiologicalSciences vol 273 no 1599 pp 2327ndash2333 2006

[92] A Gomez L D Kramer A P Dupuis II et al ldquoExperimentalinfection of eastern gray squirrels (Sciurus carolinensis) withWest Nile virusrdquoTheAmerican Journal of Tropical Medicine andHygiene vol 79 no 3 pp 447ndash451 2008

[93] K B Platt B J Tucker P G Halbur et al ldquoWest Nile virusviremia in eastern chipmunks (Tamias striatus) sufficient forinfecting different mosquitoesrdquo Emerging Infectious Diseasesvol 13 no 6 pp 831ndash837 2007

[94] K B Platt B J Tucker P GHalbur et al ldquoFox squirrels (Sciurusniger) develop West Nile virus viremias sufficient for infectingselect mosquito speciesrdquo Vector-Borne and Zoonotic Diseasesvol 8 no 2 pp 225ndash233 2008

[95] J J Root ldquoWest Nile virus associations in wild mammals asynthesisrdquoArchives of Virology vol 158 no 4 pp 735ndash752 2013

[96] S Tiawsirisup K B Platt B J Tucker and W A RowleyldquoEastern cottontail rabbits (Sylvilagus floridanus) develop WestNile virus viremias sufficient for infecting select mosquitospeciesrdquo Vector-Borne and Zoonotic Diseases vol 5 no 4 pp342ndash350 2005

[97] F Rodhain J J Petter R Albignac P Coulanges and CHannoun ldquoArboviruses and lemurs in Madagascar experi-mental infection of Lemur fulvus with yellow fever and WestNile virusesrdquo The American Journal of Tropical Medicine andHygiene vol 34 no 4 pp 816ndash822 1985

[98] M A Kostiukov Z E Gordeeva V P Bulychev N V Nemovaand O A Daniiarov ldquoThe lake frog (Rana ridibunda)mdashone ofthe food hosts of blood-sucking mosquitoes in Tadzhikistanmdasha reservoir of the West Nile fever virusrdquo Meditsinskaya Parazi-tologiya i Parazitarnye Bolezni no 3 pp 49ndash50 1985

[99] L N Pealer A A Marfin L R Petersen et al ldquoTransmission ofWest Nile virus through blood transfusion in the United Statesin 2002rdquoThe New England Journal of Medicine vol 349 no 13pp 1236ndash1245 2003

[100] M Iwamoto D B Jernigan A Guasch et al ldquoTransmissionof West Nile virus from an organ donor to four transplant


recipientsrdquo The New England Journal of Medicine vol 348 no22 pp 2196ndash2203 2003

[101] ldquoIntrauterine West Nile virus infectionmdashNew York 2002rdquoMorbidity andMortality Weekly Report vol 51 no 50 pp 1135ndash1136 2002

[102] A F Hinckley D R OrsquoLeary and E B Hayes ldquoTransmission ofWest Nile virus through human breast milk seems to be rarerdquoPediatrics vol 119 no 3 pp e666ndashe671 2007

[103] Centers for Disease Control and Prevention (CDC) ldquoPossibleWest Nile virus transmission to an infant through breast-feedingmdashMichiganrdquo MMWR Morb Mortal Wkly Rep vol 51no 39 pp 877ndash878 2002

[104] Centers for Disease Control and Prevention ldquoFatal west nilevirus infection after probable transfusion-associated trans-mission Coloradordquo MMWR Morbidity and Mortality WeeklyReport vol 62 no 31 p 622-624 2013

[105] L R Petersen and M P Busch ldquoTransfusion-transmittedarbovirusesrdquo Vox Sanguinis vol 98 no 4 pp 495ndash503 2010

[106] S PMontgomery J A BrownMKuehnert et al ldquoTransfusion-associated transmission of West Nile virus United States 2003through 2005rdquoTransfusion vol 46 no 12 pp 2038ndash2046 2006

[107] G M Meny L Santos-Zabala A Szallasi and S L StramerldquoWest Nile virus infection transmitted by granulocyte transfu-sionrdquo Blood vol 117 no 21 pp 5778ndash5779 2011

[108] Centers for Disease Control and Prevention ldquoEntomologyrdquo2009 httpwwwcdcgovncidoddvbidwestnilemosquito-Specieshtm

[109] M J Turell D J Dohm M R Sardelis M L OrsquoGuinn TG Andreadis and J A Blow ldquoAn update on the potential ofNorth American mosquitoes (Diptera Culicidae) to transmitWest Nile virusrdquo Journal of Medical Entomology vol 42 no 1pp 57ndash62 2005

[110] A M Kilpatrick L D Kramer S R Campbell E O AlleyneA P Dobson and P Daszak ldquoWest Nile virus risk assessmentand the bridge vector paradigmrdquo Emerging Infectious Diseasesvol 11 no 3 pp 425ndash429 2005

[111] M J Turell M R Sardelis M L OrsquoGuinn and D J DohmldquoPotential vectors ofWestNile virus inNorthAmericardquoCurrentTopics in Microbiology and Immunology vol 267 pp 241ndash2522002

[112] T G Andreadis ldquoThe contribution of culex pipiens complexmosquitoes to transmission and persistence of west nile virusin North Americardquo Journal of the American Mosquito ControlAssociation vol 28 no 4 pp 137ndash151 2012

[113] T Balenghien M Vazeille M Grandadam et al ldquoVectorcompetence of some French Culex and Aedes mosquitoes forWest Nile virusrdquo Vector-Borne and Zoonotic Diseases vol 8 no5 pp 589ndash595 2008

[114] P G Jupp ldquoLaboratory studies on the transmission ofWest Nilevirus by Culex (Culex) univittatusTheobald factors influencingthe transmission raterdquo Journal ofMedical Entomology vol 11 no4 pp 455ndash458 1974

[115] J S Mackenzie M D Lindsay R J Coelen A K Broom RA Hall and D W Smith ldquoArboviruses causing human diseasein the Australasian zoogeographic regionrdquo Archives of Virologyvol 136 no 3-4 pp 447ndash467 1994

[116] J Munoz S Ruiz R Soriguer et al ldquoFeeding patterns ofpotential West Nile virus vectors in South-West Spainrdquo PLoSONE vol 7 no 6 article e39549 2012

[117] MM Abbassy M Osman and A S Marzouk ldquoWest Nile virus(Flaviviridae Flavivirus) in experimentally infected Argas ticks

(Acari Argasidae)rdquo The American Journal of Tropical Medicineand Hygiene vol 48 no 5 pp 726ndash737 1993

[118] P Formosinho andMM Santos-Silva ldquoExperimental infectionof Hyalomma marginatum ticks with West Nile virusrdquo ActaVirologica vol 50 no 3 pp 175ndash180 2006

[119] H J Hutcheson C H Gorham C Machain-Williams et alldquoExperimental transmission of West Nile virus (FlaviviridaeFlavivirus) by Carios capensis ticks from North AmericardquoVector-Borne and Zoonotic Diseases vol 5 no 3 pp 293ndash2952005

[120] C H Lawrie N Y Uzcategui E A Gould and P A NuttallldquoIxodid and argasid tick species and west nile virusrdquo EmergingInfectious Diseases vol 10 no 4 pp 653ndash657 2004

[121] O W Lwande J Lutomiah V Obanda et al ldquoIsolation oftick and mosquito-borne arboviruses from ticks sampled fromlivestock and wild animal hosts in Ijara District KenyardquoVector-Borne and Zoonotic Diseases vol 13 no 9 pp 637ndash642 2013

[122] A V Bode J J Sejvar W J Pape G L Campbell and A AMarfin ldquoWest Nile Virus disease a descriptive study of 228patients hospitalized in a 4-county region of Colorado in 2003rdquoClinical Infectious Diseases vol 42 no 9 pp 1234ndash1240 2006

[123] P J Carson S M Borchardt B Custer et al ldquoNeuroinvasivedisease andwest nile virus infection NorthDakota USA 1999ndash2008rdquo Emerging Infectious Diseases vol 18 no 4 pp 684ndash6862012

[124] K Danis A Papa G Theocharopoulos et al ldquoOutbreak ofWest Nile virus infection in Greece 2010rdquo Emerging InfectiousDiseases vol 17 no 10 pp 1868ndash1872 2011

[125] C M Jean S Honarmand J K Louie and C A Glaser ldquoRiskfactors for West Nile virus neuroinvasive disease California2005rdquo Emerging Infectious Diseases vol 13 no 12 pp 1918ndash19202007

[126] E Kopel Z Amitai H Bin L M Shulman E Mendelsonand R Shefer ldquoSurveillance of west Nile virus disease Tel Avivdistrict Israel 2005 to 2010rdquo Eurosurveillance vol 16 no 252011

[127] N P Lindsey E B Hayes J E Staples and M FischerldquoWest Nile virus disease in children United States 1999ndash2007rdquoPediatrics vol 123 no 6 pp e1084ndashe1089 2009

[128] N P Lindsey J Erin Staples J A Lehman and M FischerldquoSurveillance for human west Nile virus disease-United States1999ndash2008rdquoMorbidity and Mortality Weekly Report vol 59 no2 pp 1ndash17 2010

[129] N P Lindsey J E Staples J A Lehman and M FischerldquoMedical risk factors for severe West Nile virus disease UnitedStates 2008ndash2010rdquo The American Journal of Tropical Medicineand Hygiene vol 87 no 1 pp 179ndash184 2012

[130] D Nash F Mostashari A Fine et al ldquoThe outbreak of WestNile virus infection in the New York City area in 1999rdquo TheNewEngland Journal ofMedicine vol 344 no 24 pp 1807ndash18142001

[131] J L Patnaik H Harmon and R L Vogt ldquoFollow-up of 2003humanWest Nile virus infections Denver Coloradordquo EmergingInfectious Diseases vol 12 no 7 pp 1129ndash1131 2006

[132] E B Hayes and D R OrsquoLeary ldquoWest Nile virus infection apediatric perspectiverdquo Pediatrics vol 113 no 5 pp 1375ndash13812004

[133] F Mostashari M L Bunning P T Kitsutani et al ldquoEpidemicWest Nile encephalitis New York 1999 results of a household-based seroepidemiological surveyrdquo The Lancet vol 358 no9278 pp 261ndash264 2001


[134] S Zou G A Foster R Y Dodd L R Petersen and S LStramer ldquoWestNile fever characteristics among viremic personsidentified through blood donor screeningrdquo Journal of InfectiousDiseases vol 202 no 9 pp 1354ndash1361 2010

[135] J D Fratkin A A Leis D S Stokic S A Slavinski and R WGeiss ldquopinal cord neuropathology in human West Nile virusinfectionrdquo Archives of Pathology and Laboratory Medicine vol128 no 5 pp 533ndash537 2004

[136] M P Busch D J Wright B Custer et al ldquoWest nile virusinfections projected from blood donor screening data UnitedStates 2003rdquoEmerging InfectiousDiseases vol 12 no 3 pp 395ndash402 2006

[137] G A F Ladbury M Gavana K Danis et al ldquoPopulationseroprevalence study after aWest Nile virus lineage 2 epidemicGreece 2010rdquo PLoS ONE vol 8 no 11 Article ID e80432 2013

[138] D S Asnis R Conetta G Waldman and A A TeixeiraldquoTheWest Nile virus encephalitis outbreak in the United States(1999ndash2000) from Flushing New York to beyond its bordersrdquoAnnals of the NewYork Academy of Sciences vol 951 pp 161ndash1712001

[139] R Brilla M Block G Geremia and M Wichter ldquoClinicaland neuroradiologic features of 39 consecutive cases of WestNile Virus meningoencephalitisrdquo Journal of the NeurologicalSciences vol 220 no 1-2 pp 37ndash40 2004

[140] M Emig and D J Apple ldquoSevere West Nile virus disease inhealthy adultsrdquo Clinical Infectious Diseases vol 38 no 2 pp289ndash292 2004

[141] A L Klee B Maldin B Edwin et al ldquoLong-term prognosis forclinical West Nile virus infectionrdquo Emerging Infectious Diseasesvol 10 no 8 pp 1405ndash1411 2004

[142] K OMurray S Baraniuk M Resnick et al ldquoClinical investiga-tion of hospitalized human cases of West Nile virus infectionin Houston Texas 2002ndash2004rdquo Vector-Borne and ZoonoticDiseases vol 8 no 2 pp 167ndash174 2008

[143] J J Sejvar M B Haddad B C Tierney et al ldquoNeurologicmanifestations and outcome of West Nile virus infectionrdquo TheJournal of the American Medical Association vol 290 no 4 pp511ndash515 2003

[144] D Weiss D Carr J Kellachan et al ldquoClinical findings of WestNile virus infection in hospitalized patients New York andNewJersey 2000rdquo Emerging Infectious Diseases vol 7 no 4 pp 654ndash658 2001

[145] C Klein I Kimiagar L Pollak et al ldquoNeurological features ofWestNileVirus infection during the 2000 outbreak in a regionalhospital in Israelrdquo Journal of the Neurological Sciences vol 200no 1-2 pp 63ndash66 2002

[146] C Pepperell N Rau S Krajden et al ldquoWest Nile virus infectionin 2002 morbidity and mortality among patients admitted tohospital in southcentralOntariordquoCanadianMedical AssociationJournal vol 168 no 11 pp 1399ndash1405 2003

[147] A Sribu C S Ceianu R I Panculescu-Gatej et al ldquoOutbreak ofWest Nile virus infection in humans Romania July to October2010rdquo Eurosurveillance vol 16 no 2 2011

[148] M Loeb S Hanna L Nicolle et al ldquoPrognosis after West Nilevirus infectionrdquo Annals of Internal Medicine vol 149 no 4 pp232ndash241 2008

[149] J R Sadek S A Pergam J A Harrington et al ldquoPersistentneuropsychological impairment associatedwithWestNile virusinfectionrdquo Journal of Clinical and Experimental Neuropsychol-ogy vol 32 no 1 pp 81ndash87 2010

[150] R L Cook X Xu E J Yablonsky et al ldquoDemographic andclinical factors associated with persistent symptoms after WestNile virus infectionrdquoTheAmerican Journal of Tropical Medicineand Hygiene vol 83 no 5 pp 1133ndash1136 2010

[151] M S Nolan A S Podoll A M Hause K M Akers K WFinkel and K OMurray ldquoPrevalence of chronic kidney diseaseand progression of disease over time among patients enrolledin the Houston west Nile virus cohortrdquo PLoS ONE vol 7 no 7Article ID e40374 2012

[152] T J Gray J N Burrow P G Markey et al ldquoCase report Westnile virus (Kunjin subtype) disease in the Northern Territoryof Australiamdasha case of encephalitis and review of all reportedcasesrdquoThe American Journal of Tropical Medicine and Hygienevol 85 no 5 pp 952ndash956 2011

[153] A R McMullen H Albayrak F J May C T Davis D W CBeasley and A D T Barrett ldquoMolecular evolution of lineage 2West Nile virusrdquo Journal of General Virology vol 94 no 2 pp318ndash325 2013

[154] M Venter S Human D Zaayman et al ldquoLineage 2 WestNile virus as cause of fatal neurologic disease in horses SouthAfricardquo Emerging Infectious Diseases vol 15 no 6 pp 877ndash8842009

[155] M Venter and R Swanepoel ldquoWest Nile virus lineage 2 as acause of zoonotic neurological disease in humans and horses inSouthern Africardquo Vector-Borne and Zoonotic Diseases vol 10no 7 pp 659ndash664 2010

[156] D Zaayman and M Venter ldquoWest nile virus neurologic diseasein Humans South Africa September 2008-May 2009rdquo Emerg-ing Infectious Diseases vol 18 no 12 pp 2051ndash2054 2012

[157] K C Smithburn and R H Jacobs ldquoNeutralization-tests againstneurotropic viruses with sera collected in central AfricardquoJournal of Immunology vol 44 pp 9ndash23 1942

[158] F NMacnamara DWHorn and J S Porterfield ldquoYellow feverand other arthropod-borne viruses a consideration of two sero-logical surveys made in SouthWestern Nigeriardquo Transactions ofthe Royal Society of Tropical Medicine amp Hygiene vol 53 no 2pp 202ndash212 1959

[159] R H Kokernot K C Smithburn and M P WeinbrenldquoNeutralizing antibodies to arthropod-borne viruses in humanbeings and animals in the Union of South Africardquo Journal ofImmunology vol 77 no 5 pp 313ndash323 1956

[160] J L Melnick J R Paul J T Riordan V H Barnett NGoldblum and E Zabin ldquoIsolation from human sera in Egyptof a virus apparently identical to West Nile virusrdquo Proceedingsof the Society for Experimental Biology andMedicine vol 77 no4 pp 661ndash665 1951

[161] K C Smithburn RM Taylor F Rizk andA Kader ldquoImmunityto certain arthropod-borne viruses among indigenous residentsof Egyptrdquo The American Journal of Tropical Medicine andHygiene vol 3 no 1 pp 9ndash18 1954

[162] R M Taylor H S Hurlbut H R Dressler E W Spanglerand D Thrasher ldquoIsolation of West Nile virus from Culexmosquitoesrdquo The Journal of the Egyptian Medical Associationvol 36 no 3 pp 199ndash208 1953

[163] T Briese A Rambaut M Pathmajeyan et al ldquoPhylogeneticanalysis of a human isolate from the 2000 Israel West Nile virusepidemicrdquo Emerging Infectious Diseases vol 8 no 5 pp 528ndash531 2002

[164] M Hindiyeh L M Shulman E Mendelson L Weiss ZGrossman and H Bin ldquoIsolation and characterization of WestNile virus from the blood of viremic patients during the 2000


outbreak in Israelrdquo Emerging Infectious Diseases vol 7 no 4pp 748ndash750 2001

[165] European Centre for Disease Prevention and Control ldquoHis-torical datardquo 2013 httpecdceuropaeuenhealthtopicswestnile feverWest-Nile-fever-mapsPageshistorical-dataaspx

[166] European Centre for Disease Prevention and Control ldquoWestNile fever mapsrdquo 2013 httpecdceuropaeuenhealthtopicswest nile feverWest-Nile-fever-mapsPagesindexaspx

[167] E Anis I Grotto E Mendelson et al ldquoWest Nile fever in Israelthe reemergence of an endemic diseaserdquo Journal of Infection vol68 no 2 pp 170ndash175 2014

[168] K Ergunay N Ozer D Us et al ldquoSeroprevalence of West Nilevirus and tick-borne encephalitis virus in Southeastern Turkeyfirst evidence for tick-borne encephalitis virus infectionsrdquoVector-Borne and Zoonotic Diseases vol 7 no 2 pp 157ndash1612007

[169] O Meco ldquoWest Nile arbovirus antibodies with hemagglu-tination inhibition (HI) in residents of Southeast AnatoliardquoMikrobiyoloji Bulteni vol 11 no 1 pp 3ndash17 1977

[170] N Ozer K Ergunay F Simsek et al ldquoWest Nile virus studies inthe Sanliurfa Province of Turkeyrdquo Journal of Vector Ecology vol32 no 2 pp 202ndash206 2007

[171] A Ozkul Y Yildirim D Pinar A Akcali V Yilmaz and DColak ldquoSerological evidence of West Nile Virus (WNV) inmammalian species in Turkeyrdquo Epidemiology amp Infection vol134 no 4 pp 826ndash829 2006

[172] A Radda ldquoStudies on the activity and ecology of arbovirusesin Turkeyrdquo Zentralblatt fur Bakteriologie Parasitenkunde Infek-tionskrankheiten und Hygiene Erste Abteilung Originale vol225 no 1 pp 19ndash26 1973

[173] H Kalaycioglu G Korukluoglu A Ozkul et al ldquoEmergence ofWest Nile virus infections in humans in Turkey 2010 to 2011rdquoEurosurveillance vol 17 no 21 2012

[174] K Naficy and S Saidi ldquoSerological survey on viral antibodiesin Iranrdquo Tropical and Geographical Medicine vol 22 no 2 pp183ndash188 1970

[175] S Chinikar A Javadi B Ataei et al ldquoDetection of West Nilevirus genome and specific antibodies in Iranian encephalitispatientsrdquo Epidemiology and Infection vol 140 no 8 pp 1525ndash1529 2012

[176] F Ahmadnejad V Otarod M H Fallah et al ldquoSpread ofWest Nile virus in Iran a cross-sectional serosurvey in equines2008ndash2009rdquo Epidemiology and Infection vol 139 no 10 pp1587ndash1593 2011

[177] A Batieha E K Saliba R Graham E Mohareb Y Hijazi andP Wijeyaratne ldquoSeroprevalence of West Nile Rift Valley andsandfly arboviruses in Hashimiah Jordanrdquo Emerging InfectiousDiseases vol 6 no 4 pp 358ndash362 2000

[178] P Gallian P de Micco and P Ghorra ldquoSeroprevalence of WestNile virus in blood donors at Hotel Dieu de France BeirutLebanonrdquo Transfusion vol 50 no 5 pp 1156ndash1158 2010

[179] G A Garabedian R M Matossian and M N MusallildquoSerologic evidence of arbovirus infection in Lebanonrdquo JournalMedical Libanais vol 24 no 4 pp 339ndash350 1971

[180] S M Abutarbush and A M Al-Majali ldquoWest Nile virusinfection in horses in Jordan clinical cases seroprevalence andrisk factorsrdquo Transboundary and Emerging Diseases vol 61supplement 1 pp 1ndash6 2014

[181] O Cabre M Grandadam J-L Marie et al ldquoWest Nile virus inhorses sub-Saharan Africardquo Emerging Infectious Diseases vol12 no 12 pp 1958ndash1960 2006

[182] R C Kading E M Borland M Cranfield and A M PowersldquoPrevalence of antibodies to alphaviruses and flaviviruses infree-ranging game animals and nonhuman primates in thegreater Congo basinrdquo Journal of Wildlife Diseases vol 49 no3 pp 587ndash599 2013

[183] W Sghaier O Bahri E Kedous et al ldquoRetrospective studyof viral causes of central nervous system infections in Tunisia(2003ndash2009)rdquo Medecine et Sante Tropicales vol 22 no 4 pp373ndash378 2012

[184] J C Morrill B K Johnson C Hyams et al ldquoSerologicalevidence of arboviral infections among humans of coastalKenyardquo Journal of Tropical Medicine and Hygiene vol 94 no3 pp 166ndash168 1991

[185] T B Hassine S Hammami H Elghoul and A GhramldquoDetection of circulation of West Nile virus in equine in theNorth-west of Tunisiardquo Bulletin de la Societe de PathologieExotique vol 104 no 4 pp 266ndash271 2011

[186] H El Rhaffouli M El Harrak C Lotfi et al ldquoSerologic evidenceof West Nile Virus infection among humans Moroccordquo Emerg-ing Infectious Diseases vol 18 no 5 pp 880ndash881 2012

[187] H Fassil M El Harrak and J-L Marie ldquoEpidemiologicalaspects of west Nile virus infection in Moroccordquo Medecine etsante tropicales vol 22 no 2 pp 123ndash125 2012

[188] M Gabriel P Emmerich C Frank et al ldquoIncrease in WestNile virus infections imported to Germany in 2012rdquo Journal ofClinical Virology vol 58 no 3 pp 587ndash589 2013

[189] A Soliman E Mohareb D Salman et al ldquoStudies onWest Nilevirus infection in Egyptrdquo Journal of Infection and Public Healthvol 3 no 2 pp 54ndash59 2010

[190] M Venter S Human S VanNiekerk JWilliams C van Eedenand F Freeman ldquoFatal neurologic disease and abortion in mareinfected with lineage 1 West Nile virus South Africardquo EmergingInfectious Diseases vol 17 no 8 pp 1534ndash1536 2011

[191] S Larrieu E Cardinale P Ocquidant et al ldquoCase reporta fatal neuroinvasive West Nile virus infection in a travelerreturning from Madagascar clinical epidemiological and vet-erinary investigationsrdquo American Journal of Tropical Medicineand Hygiene vol 89 no 2 pp 211ndash213 2013

[192] E S Jentes J Robinson B W Johnson et al ldquoAcute arboviralinfections in Guinea West Africa 2006rdquoThe American Journalof Tropical Medicine and Hygiene vol 83 no 2 pp 388ndash3942010

[193] W Wang F Sarkodie K Danso et al ldquoSeroprevalence of WestNile virus in GhanardquoViral Immunology vol 22 no 1 pp 17ndash222009

[194] J M M Lawson D Mounguengui M Ondounda B NEdzang J Vandji and R Tchoua ldquoA case of meningo-encephalitis due to West Nile virus in Libreville GabonrdquoMedecine Tropicale vol 69 no 5 pp 501ndash502 2009

[195] M Baba C H Logue B Oderinde et al ldquoEvidence of arbovirusco-infection in suspected febrilemalaria and typhoid patients inNigeriardquo Journal of Infection in Developing Countries vol 7 no1 pp 51ndash59 2013

[196] A G Fall A Diaıte M T Seck et al ldquoWest Nile virustransmission in sentinel chickens and potential mosquito vec-tors Senegal River Delta 2008-2009rdquo International Journal ofEnvironmental Research and Public Health vol 10 no 10 pp4718ndash4727 2013

[197] M K Faulde M Spiesberger and B Abbas ldquoSentinel site-enhanced near-real time surveillance documenting West Nilevirus circulation in two Culex mosquito species indicating


different transmission characteristics Djibouti City DjiboutirdquoJournal of the Egyptian Society of Parasitology vol 42 no 2 pp461ndash474 2012

[198] C Ochieng J Lutomiah A Makio et al ldquoMosquito-bornearbovirus surveillance at selected sites in diverse ecologicalzones of Kenya 2007ndash2012rdquoVirology Journal vol 10 article 1402013

[199] K C Smithburn J A Kerr and P B Gatne ldquoNeutralizingantibodies against certain viruses in the sera of residents ofIndiardquo The Journal of Immunology vol 72 no 4 pp 248ndash2571954

[200] T R Rao ldquoImmunological surveys of arbovirus infections inSouth-EastAsia with special reference to dengue chikungunyaand Kyasanur Forest diseaserdquo Bulletin of the World HealthOrganization vol 44 no 5 pp 585ndash591 1971

[201] J Shukla D Saxena S Rathinam et al ldquoMolecular detectionand characterization of West Nile virus associated with mul-tifocal retinitis in patients from southern Indiardquo InternationalJournal of Infectious Diseases vol 16 no 1 pp e53ndashe59 2012

[202] A Balakrishnan D K Butte and S M Jadhav ldquo Completegenome sequence of west nile virus isolated from Alappuzhadistrict Kerala Indiardquo Genome Announcements vol 1 no 32013

[203] S George S R Prasad J A Rao P N Yergolkar and C V SettyldquoIsolation of Japanese encephalitis amp West Nile viruses fromfatal cases of encephalitis in Kolar district of Karnatakardquo TheIndian Journal of Medical Research vol 86 pp 131ndash134 1987

[204] SAKhan PDutta AMKhan et al ldquoWest nile virus infectionAssam Indiardquo Emerging Infectious Diseases vol 17 no 5 pp947ndash948 2011

[205] S A Khan P Dutta P Chowdhury J Borah R Topno andJ Mahanta ldquoCo-infection of arboviruses presenting as acuteEncephalitis Syndromerdquo Journal of Clinical Virology vol 51 no1 pp 5ndash7 2011

[206] M A Darwish H Hoogstraal T J Roberts I P Ahmed and FOmar ldquoA sero-epidemiological survey for certain arboviruses(Togaviridae) in Pakistanrdquo Transactions of the Royal Society ofTropical Medicine and Hygiene vol 77 no 4 pp 442ndash445 1983

[207] C G Hayes S Baqar T Ahmed M A Chowdhry and W KReisen ldquoWest Nile virus in Pakistan 1 Sero-epidemiologicalstudies in Punjab Provincerdquo Transactions of the Royal Society ofTropical Medicine and Hygiene vol 76 no 4 pp 431ndash436 1982

[208] A Igarashi M Tanaka K Morita et al ldquoDetection of WestNile and Japanese encephalitis viral genome sequences incerebrospinal fluid from acute encephalitis cases in KarachiPakistanrdquo Microbiology and Immunology vol 38 no 10 pp827ndash830 1994

[209] M Sugamata A Ahmed T Miura et al ldquoSeroepidemiologicalstudy of infection with West Nile virus in Karachi Pakistan in1983 and 1985rdquo Journal of Medical Virology vol 26 no 3 pp243ndash247 1988

[210] Centers forDiseaseControl andPrevention International Cata-log of Arboviruses Including Certain Other Viruses of VertebratesCenters for Disease Control and Prevention Atlanta Ga USA2014

[211] C Y Ching J Casals E T Bowen et al ldquoArbovirus infections inSarawak the isolation of Kunjin virus from mosquitoes of theCulex pseudovishnui grouprdquo Annals of Tropical Medicine andParasitology vol 64 no 3 pp 263ndash268 1970

[212] N Karabatsos American Society of Tropical Medicine andHygiene American Committee on Arthropod-borne Viruses

and and Rockefeller Foundation International Catalogue ofArboviruses Including Certain Other Viruses of VertebratesAmerican Society of Tropical Medicine and Hygiene for TheSubcommittee on Information Exchange of the AmericanCommittee on Arthropod-borne Viruses 1985

[213] W Rutvisuttinunt S K Shrestha P Chinnawirotpisan et alldquoEvidence of West Nile virus infection in Nepalrdquo in Proceedingsof the 62nd American Society of Tropical Medicine and HygieneAnnual Meeting Washington DC USA November 2013

[214] X L Li S H Fu W B Liu et al ldquoWest nile virus infection inXinjiang Chinardquo Vector-Borne and Zoonotic Diseases vol 13no 2 pp 131ndash133 2013

[215] Q R Yang ldquoA study on arboviruse antibodies of birds in theNiao-Diao-Mountain area Eryan-county of Yunnan provincerdquoZhong Hua Liu Xing Bing Xue Za Zhi vol 9 no 3 pp 150ndash1531988

[216] D L Lan C S Wang B Deng et al ldquoSerological investigationson West Nile virus in birds and horses in Shanghai ChinardquoEpidemiology and Infection vol 141 no 3 pp 596ndash600 2013

[217] D Lan W Ji D Yu et al ldquoSerological evidence of West Nilevirus in dogs and cats in Chinardquo Archives of Virology vol 156no 5 pp 893ndash895 2011

[218] J Y Yeh J Y Park and E N Ostlund ldquoSerologic evidenceof West Nile Virus in wild ducks captured in major inlandresting sites formigratorywaterfowl in SouthKoreardquoVeterinaryMicrobiology vol 154 no 1-2 pp 96ndash103 2011

[219] R L Doherty J G Carley M J Mackerras and E N MarksldquoStudies of arthropod-borne virus infections inQueensland IIIIsolation and characterization of virus strains fromwild-caughtmosquitoes in North Queenslandrdquo The Australian Journal ofExperimental Biology and Medical Science vol 41 pp 17ndash391963

[220] F X Heinz M S Collett R H Purcel et al ldquoFamily fla-viviridaerdquo in Virus Taxonomy Classification and Nomenclatureof Viruses M H V van Regenmortel M F Fauquet D HL Bishop R J M Moormann and etal Eds pp 859ndash878Academic Press San Diego Calif USA 1st edition 2000

[221] R C Russell and D E Dwyer ldquoArboviruses associated withhuman disease in Australiardquo Microbes and Infection vol 2 no14 pp 1693ndash1704 2000

[222] M J Frost J Zhang J H Edmonds et al ldquoCharacterization ofvirulentWestNile virusKunjin strainAustralia 2011rdquoEmergingInfectious Diseases vol 18 no 5 pp 792ndash800 2012

[223] R A Mann M Fegan K OrsquoRiley J Motha and S WarnerldquoMolecular characterization and phylogenetic analysis of Mur-ray Valley encephalitis virus and West Nile virus (Kunjinsubtype) from an arbovirus disease outbreak in horses inVictoria Australia in 2011rdquo Journal of Veterinary DiagnosticInvestigation vol 25 no 1 pp 35ndash44 2013

[224] N A Prow ldquoThe changing epidemiology of Kunjin virus inAustraliardquo International Journal of Environmental Research andPublic Health vol 10 no 12 pp 6255ndash6272 2013

[225] S A Williams J S Richards H M Faddy et al ldquoLowseroprevalence of murray valley encephalitis and kunjin virusesin an opportunistic serosurvey Victoria 2011rdquo Australian andNew Zealand Journal of Public Health vol 37 no 5 pp 427ndash4332013

[226] V Bardos J Adamcova S Dedei N Gjini B Rosicky andA Simkova ldquoNeutralizing antibodies against some neurotropicviruses determined in human sera in Albaniardquo Journal ofHygiene Epidemiology Microbiology and Immunology vol 3pp 277ndash282 1959


[227] Z Hubalek and J Halouzka ldquoWest Nile fevermdasha reemergingmosquito-borne viral disease in Europerdquo Emerging InfectiousDiseases vol 5 no 5 pp 643ndash650 1999

[228] A R Filipe ldquoIsolation in Portugal of West Nile virus fromAnopheles maculipennis mosquitoesrdquo Acta Virologica vol 16no 4 article 361 1972

[229] E Ernek O Kozuch J Nosek J Teplan and C FolkldquoArboviruses in birds captured in Slovakiardquo Journal of HygieneEpidemiology Microbiology and Immunology vol 21 no 3 pp353ndash359 1977

[230] Z Hubalek J Halouzka Z Juricova and O Sebesta ldquoFirstisolation of mosquito-borne west nile virus in the CzechRepublicrdquo Acta Virologica vol 42 no 2 pp 119ndash120 1998

[231] E Molnar M S Gulyas L Kubinyi et al ldquoStudies on the occur-rence of tick-borne encephalitis in Hungaryrdquo Acta veterinariaAcademiae Scientiarum Hungaricae vol 26 no 4 pp 419ndash4371976

[232] H G Zeller and I Schuffenecker ldquoWest Nile virus an overviewof its spread in Europe and the Mediterranean basin in contrastto its spread in the Americasrdquo European Journal of ClinicalMicrobiology and Infectious Diseases vol 23 no 3 pp 147ndash1562004

[233] P Couissinier-Paris ldquoWest Nile virus in Europe and Africa stillminor pathogen or potential threat to public healthrdquo Bulletinde la Societe de Pathologie Exotique vol 99 no 5 pp 348ndash3542006

[234] T Bakonyi E Ferenczi K Erdelyi et al ldquoExplosive spread ofa neuroinvasive lineage 2 West Nile virus in Central Europe20082009rdquoVeterinary Microbiology vol 165 no 1-2 pp 61ndash702013

[235] P Calistri A Giovannini Z Hubalek et al ldquoEpidemiology ofWest Nile in Europe and in theMediterranean basinrdquoTheOpenVirology Journal vol 4 pp 29ndash37 2010

[236] B Murgue S Murri S Zientara B Durand J-P Durand andH Zeller ldquoWest Nile outbreak in horses in Southern France2000 the return after 35 yearsrdquo Emerging Infectious Diseasesvol 7 no 4 pp 692ndash696 2001

[237] A Mailles P Dellamonica H Zeller et al ldquoHuman and equineWest Nile virus infections in France August-September 2003rdquoEurosurveillance vol 7 no 43 article 1 2003 httpwwweurosurveillanceorgViewArticleaspxArticleId=2312

[238] B Durand G Dauphin H Zeller et al ldquoSerosurvey for WestNile virus in horses in southern Francerdquo Veterinary Record vol157 no 22 pp 711ndash713 2005

[239] G L Autorino A Battisti V Deubel et al ldquoWest Nile virusepidemic in horses Tuscany region Italyrdquo Emerging InfectiousDiseases vol 8 no 12 pp 1372ndash1378 2002

[240] G Rezza ldquoChikungunya and West Nile virus outbreaks whatis happening in north-eastern Italyrdquo European Journal of PublicHealth vol 19 no 3 pp 236ndash237 2009

[241] C Rizzo P Salcuni L Nicoletti et al ldquoEpidemiological surveil-lance of West Nile neuroinvasive diseases in Italy 2008 to 2011rdquoEurosurveillance vol 17 no 20 2012

[242] A E Platonov V A Tolpin K A Gridneva et al ldquoTheincidence ofwest nile disease in russia in relation to climatic andenvironmental factorsrdquo International Journal of EnvironmentalResearch and Public Health vol 11 no 2 pp 1211ndash1232 2014

[243] O Engler G Savini A Papa et al ldquoEuropean surveillance forWest Nile virus in mosquito populationsrdquo International Journalof Environmental Research and Public Health vol 10 no 10 pp4869ndash4895 2013

[244] L BarzonM Pacenti E Franchin et al ldquoLarge humanoutbreakof West Nile virus infection in north-eastern Italy in 2012rdquoViruses vol 5 no 11 pp 2825ndash2839 2013

[245] L Barzon M Pacenti E Franchin et al ldquoThe complex epi-demiological scenario of West Nile virus in Italyrdquo InternationalJournal of Environmental Research and Public Health vol 10 no10 pp 4669ndash4689 2013

[246] L Barzon M Pacenti E Franchin et al ldquoWhole genomesequencing and phylogenetic analysis ofWest Nile virus lineage1 and lineage 2 from human cases of infection Italy August2013rdquo Eurosurveillance vol 18 no 38 Article ID 20597 2013

[247] C Napoli A Bella S Declich et al ldquoIntegrated humansurveillance systems of West Nile virus infections in Italythe 2012 experiencerdquo International Journal of EnvironmentalResearch and Public Health vol 10 no 12 pp 7180ndash7192 2013

[248] A Papa E Papadopoulou E Gavana S Kalaitzopoulou andS Mourelatos ldquoDetection of west nile virus lineage 2 in culexmosquitoes Greece 2012rdquo Vector-Borne and Zoonotic Diseasesvol 13 no 9 pp 682ndash684 2013

[249] I Jesus-de La Calle M J Espinosa-Garcıa S Perez-Ramosand E Cruz-Rosales ldquoFirst confirmed cases of human menin-goencephalitis due to West Nile virus in Andalusia SpainrdquoEnfermedades Infecciosas y Microbiologia Clinica vol 30 no 7pp 426ndash427 2012

[250] K Stiasny S W Aberle and F X Heinzl ldquoRetrospectiveidentification of human cases of west nile virus infection inAustria (2009 to 2010) by serological differentiation fromUsutuand other flavivirus infectionsrdquo Eurosurveillance vol 18 no 432013

[251] E Merdic L Peric N Pandak et al ldquoWest Nile virus outbreakin humans in Croatia 2012rdquo Collegium Antropologicum vol 37no 3 pp 943ndash947 2013

[252] N Popovic B Milosevic A Urosevic et al ldquoOutbreak of WestNile virus infection among humans in Serbiardquo Eurosurveillancevol 18 no 43 2013

[253] I Pem-Novosel T Vilibic-Cavlek I Gjenero-Margan et alldquoFirst outbreak of west nile virus neuroinvasive disease inhumans Croatia 2012rdquoVector-Borne andZoonoticDiseases vol14 no 1 pp 82ndash84 2014

[254] A Esteves A PGAlmeida R PGalao et al ldquoWestNile virus inSouthern Portugal 2004rdquo Vector-Borne and Zoonotic Diseasesvol 5 no 4 pp 410ndash413 2005

[255] V Sambri M Capobianchi R Charrel et al ldquoWest Nile virusin Europe emergence epidemiology diagnosis treatment andpreventionrdquo Clinical Microbiology and Infection vol 19 no 8pp 699ndash704 2013

[256] I C Kurolt V Krajinovic A Topic I Kuzman B Barsic andAMarkotic ldquoFirst molecular analysis ofWest Nile virus duringthe 2013 outbreak in Croatiardquo Virus Research vol 189 pp 63ndash66 2014

[257] T Petrovic A B Blazquez D Lupulovic et al ldquoMonitoringWest Nile virus (WNV) infection in wild birds in Serbia during2012 first isolation and characterisation of WNV strains fromSerbiardquo Eurosurveillance vol 18 no 44 2013

[258] G Savini G Capelli F Monaco et al ldquoEvidence of WestNile virus lineage 2 circulation in Northern Italyrdquo VeterinaryMicrobiology vol 158 no 3-4 pp 267ndash273 2012

[259] G Valiakos A Touloudi C Iacovakis et al ldquoMoleculardetection and phylogenetic analysis of West Nile virus lineage2 in sedentary wild birds (Eurasian magpie) Greece 2010rdquoEurosurveillance vol 16 no 18 2011


[260] E Wodak S Richter Z Bago et al ldquoDetection and molecularanalysis of West Nile virus infections in birds of prey inthe Eastern part of Austria in 2008 and 2009rdquo VeterinaryMicrobiology vol 149 no 3-4 pp 358ndash366 2011

[261] A C Brault C Y-H Huang S A Langevin et al ldquoA singlepositively selected West Nile viral mutation confers increasedvirogenesis in American crowsrdquo Nature Genetics vol 39 no 9pp 1162ndash1166 2007

[262] A Papa T Bakonyi K Xanthopoulou A Vazquez A Tenorioand N Nowotny ldquoGenetic characterization of west nile viruslineage 2 Greece 2010rdquo Emerging Infectious Diseases vol 17 no5 pp 920ndash922 2011

[263] D Morgan ldquoControl of arbovirus infections by a coordinatedresponse West Nile Virus in England and Walesrdquo FEMSImmunology and Medical Microbiology vol 48 no 3 pp 305ndash312 2006

[264] S LinkeMNiedrig AKaiser et al ldquoSerologic evidence ofWestNile virus infections in wild birds captured in Germanyrdquo TheAmerican Journal of Tropical Medicine and Hygiene vol 77 no2 pp 358ndash364 2007

[265] C Laubli S Neves da Costa Monteiro Pires C Griot and EBreidenbach ldquoWest nile virus epizootic situation in Switzer-landrdquo 2006 httpwwwbvetadminchgesundheit tiere003150031702600indexhtml

[266] V A Brugman D L Horton L P Phipps et al ldquoEpidemiolog-ical perspectives on West Nile virus surveillance in wild birdsin Great Britainrdquo Epidemiology and Infection vol 141 no 6 pp1134ndash1142 2013

[267] A Buckley A Dawson S R Moss S A Hinsley P E Bellamyand E A Gould ldquoSerological evidence ofWest Nile virus Usutuvirus and Sindbis virus infection of birds in the UKrdquo Journal ofGeneral Virology vol 84 no 10 pp 2807ndash2817 2003

[268] A Buckley A Dawson and E A Gould ldquoDetection of serocon-version toWest Nile virus Usutu virus and Sindbis virus in UKsentinel chickensrdquo Virology Journal vol 3 article 71 2006

[269] L P Phipps J P Duff J P Holmes et al ldquoSurveillance for WestNile virus in British birds (2001 to 2006)rdquoTheVeterinary Recordvol 162 no 13 pp 413ndash415 2008

[270] Z Hubalek E Wegner J Halouzka et al ldquoSerologic survey ofpotential vertebrate hosts for West Nile virus in Polandrdquo ViralImmunology vol 21 no 2 pp 247ndash253 2008

[271] R N Charrel A C Brault P Gallian et al ldquoEvolutionaryrelationship between Old World West Nile virus strains evi-dence for viral gene flow between Africa the Middle East andEuroperdquo Virology vol 315 no 2 pp 381ndash388 2003

[272] ldquoHuman West Nile virus surveillancemdashConnecticut New Jer-sey and New York 2000rdquo Morbidity and Mortality WeeklyReport vol 50 no 14 pp 265ndash268 2001

[273] C T Davis G D Ebel R S Lanciotti et al ldquoPhylogeneticanalysis of North AmericanWest Nile virus isolates 2001ndash2004evidence for the emergence of a dominant genotyperdquo Virologyvol 342 no 2 pp 252ndash265 2005

[274] G D Ebel J Carricaburu D Young K A Bernard and L DKramer ldquoGenetic and phenotypic variation of West Nile virusin New York 2000ndash2003rdquo The American Journal of TropicalMedicine and Hygiene vol 71 no 4 pp 493ndash500 2004

[275] R M Moudy M A Meola L-L L Morin G D Ebel and LD Kramer ldquoA newly emergent genotype of West Nile virus istransmitted earlier and more efficiently by Culex mosquitoesrdquoThe American Journal of Tropical Medicine and Hygiene vol 77no 2 pp 365ndash370 2007

[276] K W Snapinn E C Holmes D S Young K A Bernard L DKramer and G D Ebel ldquoDeclining growth rate of West Nilevirus in North Americardquo Journal of Virology vol 81 no 5 pp2531ndash2534 2007

[277] OKomarM B Robbins GG Contreras et al ldquoWestNile virussurvey of birds and mosquitoes in the Dominican RepublicrdquoVector-Borne and Zoonotic Diseases vol 5 no 2 pp 120ndash1262005

[278] Centers for Disease Control and Prevention ldquoWest Nile virusstatistics and mapsrdquo 2013 httpwwwcdcgovwestnilestats-Maps

[279] L R Petersen P J Carson B J Biggerstaff B Custer S MBorchardt andM P Busch ldquoEstimated cumulative incidence ofWestNile virus infection inUS adults 1999ndash2010rdquoEpidemiologyamp Infection vol 141 no 3 pp 591ndash595 2013

[280] P Sockett ldquoThe incursion and expansion ofWestNile Virus intoCanadardquo 2005 httpwwwwebbertrainingcomfileslibrarydocs26pdf

[281] Public Health Agency of Canada ldquoSummary of HumanSurveillance Table (2008ndash2012)(2002ndash2007)rdquo 2013 httpwwwphac-aspcgccawnv-vwnmon-hmnsurv-archive-engphpa-2008 12

[282] D Roth B Henry S Mak et al ldquoWest Nile Virus rangeexpansion into British Columbiardquo Emerging Infectious Diseasesvol 16 no 8 pp 1251ndash1258 2010

[283] Public Health Agency of Canada ldquoHuman Surveillancerdquo 2013httpwwwphac-aspcgccawnv-vwnmon-hmnsurv-engphp

[284] Caribbean Epidemiology Centre West Nile Virus in CaymanIslands Caribbean Epidemiology Centre Trinidad and TobagoSpain 2001

[285] A P Dupuis II P P Marra and L D Kramer ldquoSerologicevidence ofWest Nile virus transmission JamaicaWest IndiesrdquoEmerging Infectious Diseases vol 9 no 7 pp 860ndash863 2003

[286] O Komar M B Robbins K Klenk et al ldquoWest Nile virustransmission in resident birds Dominican Republicrdquo EmergingInfectious Diseases vol 9 no 10 pp 1299ndash1302 2003

[287] R Quirin M Salas S Zientara et al ldquoWest Nile VirusGuadelouperdquo Emerging Infectious Diseases vol 10 no 4 pp706ndash708 2004

[288] Caribbean Epidemiology Centre ldquoRecommendations for WestNile Surveillance in the Caribbeanrdquo 2004 httpwwwcarecorgwest-nile-2004

[289] N Komar and G G Clark ldquoWest Nile virus activity in LatinAmerica and the Caribbeanrdquo Revista Panamericana de SaludPublica vol 19 no 2 pp 112ndash117 2006

[290] M Pupo M G Guzman R Fernandez et al ldquoWest Nile virusinfection in humans and horses Cubardquo Emerging InfectiousDiseases vol 12 no 6 pp 1022ndash1024 2006

[291] A P Dupuis II P P Marra R Reitsma M J Jones K L Louieand L D Kramer ldquoShort report serologic evidence for WestNile virus transmission in Puerto Rico andCubardquoTheAmericanJournal of Tropical Medicine and Hygiene vol 73 no 2 pp 474ndash476 2005

[292] E A Hunsperger K L McElroy K Bessoff C Colon RBarrera and J L Munoz-Jordan ldquoWest Nile virus from blooddonors vertebrates andmosquitoes PuertoRico 2007rdquoEmerg-ing Infectious Diseases vol 15 no 8 pp 1298ndash1300 2009

[293] R Barrera E Hunsperger J L Munoz-Jordan et al ldquoShortreport first isolation of West Nile virus in the Caribbeanrdquo TheAmerican Journal of Tropical Medicine and Hygiene vol 78 no4 pp 666ndash668 2008


[294] M E Beatty E Hunsperger E Long et al ldquoMosquitoborneinfections after Hurricane Jeanne Haiti 2004rdquo Emerging Infec-tious Diseases vol 13 no 2 pp 308ndash310 2007

[295] J G Estrada-Franco R Navarro-Lopez D W C Beasley et alldquoWest Nile virus in Mexico evidence of widespread circulationsince July 2002rdquo Emerging Infectious Diseases vol 9 no 12 pp1604ndash1607 2003

[296] D Elizondo-Quiroga C T Davis I Fernandez-Salas et alldquoWest nile virus isolation in human and mosquitoes MexicordquoEmerging Infectious Diseases vol 11 no 9 pp 1449ndash1452 2005

[297] C Rios-Ibarra B J Blitvich J Farfan-Ale et al ldquoFatal humancase of West Nile virus disease Mexico 2009rdquo EmergingInfectious Diseases vol 16 no 4 pp 741ndash743 2010

[298] S Guerrero-Sanchez S Cuevas-Romero N M Nemeth et alldquoWest Nile virus infection of birdsMexicordquo Emerging InfectiousDiseases vol 17 no 12 pp 2245ndash2252 2011

[299] D W C Beasley C T Davis J Estrada-Franco et al ldquoGenomesequence and attenuating mutations in Nile virus isolate fromMexicordquo Emerging Infectious Diseases vol 10 no 12 pp 2221ndash2224 2004

[300] A C Brault S A Langevin W N Ramey et al ldquoReducedavian virulence and viremia of West Nile virus isolates fromMexico and Texasrdquo The American Journal of Tropical Medicineand Hygiene vol 85 no 4 pp 758ndash767 2011

[301] L Cruz V M Cardenas M Abarca et al ldquoShort reportserological evidence of West Nile virus activity in El SalvadorrdquoThe American Journal of Tropical Medicine and Hygiene vol 72no 5 pp 612ndash615 2005

[302] M E Morales-Betoulle N Komar N A Panella et al ldquoWestNile virus ecology in a tropical ecosystem in Guatemalardquo TheAmerican Journal of Tropical Medicine and Hygiene vol 88 no1 pp 116ndash126 2013

[303] J Hobson-Peters C Arevalo W Y Cheah et al ldquoDetectionof antibodies to West Nile virus in horses Costa Rica 2004rdquoVector-Borne and Zoonotic Diseases vol 11 no 8 pp 1081ndash10842011

[304] L Berrocal J Pena M Gonzalez and S Mattar ldquoWest Nilevirus ecology and epidemiology of an emerging pathogen inColombiardquo Revista de Salud Publica vol 8 no 2 pp 218ndash2282006

[305] S Mattar N Komar G Young J Alvarez and M GonzalezldquoSeroconversion forWest Nile and St Louis encephalitis virusesamong sentinel horses in Colombiardquo Memorias do InstitutoOswaldo Cruz vol 106 no 8 pp 976ndash979 2011

[306] MAMoralesM Barrandeguy C Fabbri et al ldquoWestNile virusisolation from equines in Argentina 2006rdquo Emerging InfectiousDiseases vol 12 no 10 pp 1559ndash1561 2006

[307] L A Diaz N Komar A Visintin et al ldquoWest Nile virus in birdsArgentinardquo Emerging Infectious Diseases vol 14 no 4 pp 689ndash691 2008

[308] I Bosch F Herrera J-C Navarro et al ldquoWest Nile virusVenezuelardquo Emerging Infectious Diseases vol 13 no 4 pp 651ndash653 2007

[309] A Pauvolid-Correa M A Morales S Levis et al ldquoNeutralisingantibodies for West Nile virus in horses from Brazilian Pan-tanalrdquo Memorias do Instituto Oswaldo Cruz vol 106 no 4 pp467ndash474 2011

[310] T Ometto E L Durigon J de Araujo et al ldquoWest nilevirus surveillance Brazil 2008ndash2010rdquo Transactions of the RoyalSociety of Tropical Medicine and Hygiene vol 107 no 11 ArticleID trt081 pp 723ndash730 2013

[311] V Melandri A E Guimaraes N Komar et al ldquoSerologicaldetection of West Nile virus in horses and chicken fromPantanal BrazilrdquoMemorias do Instituto Oswaldo Cruz vol 107no 8 pp 1073ndash1075 2012

[312] A Pauvolid-Correa Z Campos R Juliano J Velez R MNogueira and N Komar ldquoSerological evidence of widespreadcirculation of West Nile virus and other flaviviruses in equinesof the Pantanal Brazilrdquo PLoS Neglected Tropical Diseases vol 8Article ID e2706 2014

[313] J R Silva L C Medeiros V P Reis et al ldquoSerologic surveyof West Nile virus in horses from Central-West Northeast andSoutheast BrazilrdquoMemorias do Instituto Oswaldo Cruz vol 108no 7 pp 921ndash923 2013

[314] C N Soares M J C Castro J M Peralta M R G de Freitasand M Puccioni-Sohler ldquoIs west nile virus a potential cause ofcentral nervous system infection in BrazilrdquoArquivos de Neuro-Psiquiatria vol 68 no 5 pp 761ndash763 2010

[315] BM Forshey C Guevara V A Laguna-Torres et al ldquoArboviraletiologies of acute febrile illnesses in western south America2000ndash2007rdquo PLoS Neglected Tropical Diseases vol 4 no 8article e787 2010

[316] MMazzei G Savini DG Annapia et al ldquoWestNile seropreva-lence study in Bolivian horses 2011rdquoVector-Borne and ZoonoticDiseases vol 13 no 12 pp 894ndash896 2013

[317] J E Osorio K A Ciuoderis J G Lopera et al ldquoCharacter-ization of West Nile viruses isolated from captive Americanflamingoes (Phoenicopterus ruber) in Medellin ColombiardquoTheAmerican Journal of Tropical Medicine and Hygiene vol 87 no3 pp 565ndash572 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of


Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology


Molecular Biology International

GenomicsInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


BioinformaticsAdvances in

Marine BiologyJournal of



Signal TransductionJournal of


BioMed Research International

Evolutionary BiologyInternational Journal of



Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Genetics Research International


Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational



Enzyme Research



Microbiology


22

2

22

22

22

22

2

3 4

5

2

2

Figure 1 Global distribution of WNV by country Redmdashhuman cases or human seropositivity Bluemdashnonhumanmosquito cases orseropositivity Graymdashno data or no positives reported Black lines represent worldwide distribution of the main WNV mosquito vectorsexcluding areas of extreme climate denoted by dashed lines Circled numbers indicate the reported presence of WNV lineages other thanlineage 1 in that specific area For Japan South Korea Finland and Sweden seropositivity for WNV has been detected only in nonresidentbirds which was not considered indicative of local transmission Kading et al [182] reported infections in gorillas living near the border ofthe Democratic Republic of the Congo and Rwanda which were sampled in the DRC but may have been infected in Rwanda

5998400 UTR C pr M E NS1 a b a b

NS2NS3

NS4NS5

3998400 UTR

Structural Nonstructural

(a)

E-protein dimerMembrane

Capsid proteinprMM protein

RNA

(b)

Figure 2 WNV genome organization and virion composition (a) the viral genome is represented with one ORF encoding 3 structural and 7nonstructural proteins The 51015840 and 31015840 UTRs are indicated Structural proteins are colored green whereas nonstructural proteins are blue (b)Structure of WNV virion

the lipid bilayer of the virus during assembly and are exposedon the virion surface [32]The prM protein is thought to pro-tect the immature virion from undergoing premature fusionprior to viral budding from the cell surface by blocking thefusion loop of E and is cleaved off during the viral maturationprocess [32ndash36] During infection mature immature andpartially mature virus particles are produced containing avarying number of immature prM protein molecules on thesurface [37] The E protein mediates both binding of thereceptor on the cell surface for viral entry and fusion with themembrane of the host cell [38ndash40]

The seven nonstructural proteins are multifunctionalplaying critical roles in viral RNA synthesis andor assembly

NS1 is believed to play an early role in regulation of viralreplication [41ndash43] NS3 has multiple enzymatic functionsserving as a viral serine protease which cleaves the other non-structural proteins from the viral polyprotein in associationwith NS2B an RNA helicase in association with NS4a andan NTPase in association with NS5 [44ndash49]The NS5 proteinis necessary for viral replication containing RNA-dependentRNA polymerase (RdRp) activity in the C-terminal regionand methyltransferase activity in the N-terminal region [4150ndash53] NS2A NS2B NS4A and NS4B are small hydropho-bic proteins that have no known enzymatic functions butare believed to act as cofactors for viral replication complexassembly and localization [54ndash57]










4 Hosts and Vectors






70

98

100

93

100

100100

100

100

100100

100

100

100

005

94

100

99

100

80

71

57











Lineage 1a

Lineage 1b

Lineage 51c

Lineage 2

Lineage 3

Lineage 4


Enzootic Cycle


Epidemic

Epizootic


































8 WNV in Europe




















Year

Case

s

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

0100

2000

4000

6000

8000

10000

12000


(a)

Dea

ths

0

50

100

150

200

250

300

350

Year

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

(b)


Clin

ical

case

s

0

500

1000

1500

2000

2500

Year

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

















12 Conclusion






References





















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology










4 Hosts and Vectors






70

98

100

93

100

100100

100

100

100100

100

100

100

005

94

100

99

100

80

71

57











Lineage 1a

Lineage 1b

Lineage 51c

Lineage 2

Lineage 3

Lineage 4


Enzootic Cycle


Epidemic

Epizootic


































8 WNV in Europe




















Year

Case

s

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

0100

2000

4000

6000

8000

10000

12000


(a)

Dea

ths

0

50

100

150

200

250

300

350

Year

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

(b)


Clin

ical

case

s

0

500

1000

1500

2000

2500

Year

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

















12 Conclusion






References





















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


70

98

100

93

100

100100

100

100

100100

100

100

100

005

94

100

99

100

80

71

57











Lineage 1a

Lineage 1b

Lineage 51c

Lineage 2

Lineage 3

Lineage 4


Enzootic Cycle


Epidemic

Epizootic


































8 WNV in Europe




















Year

Case

s

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

0100

2000

4000

6000

8000

10000

12000


(a)

Dea

ths

0

50

100

150

200

250

300

350

Year

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

(b)


Clin

ical

case

s

0

500

1000

1500

2000

2500

Year

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

















12 Conclusion






References





















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology




























8 WNV in Europe




















Year

Case

s

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

0100

2000

4000

6000

8000

10000

12000


(a)

Dea

ths

0

50

100

150

200

250

300

350

Year

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

(b)


Clin

ical

case

s

0

500

1000

1500

2000

2500

Year

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

















12 Conclusion






References





















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology















Year

Case

s

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

0100

2000

4000

6000

8000

10000

12000


(a)

Dea

ths

0

50

100

150

200

250

300

350

Year

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

(b)


Clin

ical

case

s

0

500

1000

1500

2000

2500

Year

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

















12 Conclusion






References





















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology









12 Conclusion






References





















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology














































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

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