Key facts · West Nile virus can cause a fatal neurological disease in humans. · However, approximately 80% of people who are infected will not ...Home/Newsroom/Factsheets/Detail/WestNilevirusWestNilevirus3October2017KeyfactsWestNileviruscancauseafatalneurologicaldiseaseinhumans.However,approximately80%ofpeoplewhoareinfectedwillnotshowanysymptoms.WestNilevirusismainlytransmittedtopeoplethroughthebitesofinfectedmosquitoes.Theviruscancauseseverediseaseanddeathinhorses.Vaccinesareavailableforuseinhorsesbutnotyetavailableforpeople.BirdsarethenaturalhostsofWestNilevirus.WestNileVirus(WNV)cancauseneurologicaldiseaseanddeathinpeople.WNViscommonlyfoundinAfrica,Europe,theMiddleEast,NorthAmericaandWestAsia.WNVismaintainedinnatureinacycleinvolvingtransmissionbetweenbirdsandmosquitoes.Humans,horsesandothermammalscanbeinfected.WestNileVirus(WNV)isamemberoftheflavivirusgenusandbelongstotheJapaneseencephalitisantigeniccomplexofthefamilyFlaviviridae.OutbreaksWestNileVirus(WNV)wasfirstisolatedinawomanintheWestNiledistrictofUgandain1937.Itwasidentifiedinbirds(crowsandcolumbiformes)inNiledeltaregionin1953.Before1997WNVwasnotconsideredpathogenicforbirds,butatthattimeinIsraelamorevirulentstraincausedthedeathofdifferentbirdspeciespresentingsignsofencephalitisandparalysis.HumaninfectionsattributabletoWNVhavebeenreportedinmanycountriesintheWorldforover50years.In1999aWNVcirculatinginIsraelandTunisiawasimportedinNewYorkproducingalargeanddramaticoutbreakthatspreadthroughoutthecontinentalUnitedStatesofAmerica(USA)inthefollowingyears.TheWNVoutbreakinUSA(1999-2010)highlightedthatimportationandestablishmentofvector-bornepathogensoutsidetheircurrenthabitatrepresentaseriousdangertotheworld.ThelargestoutbreaksoccurredinGreece,Israel,Romania,RussiaandUSA.Outbreaksitesareonmajorbirdsmigratoryroutes.Initsoriginalrange,WNVwasprevalentthroughoutAfrica,partsofEurope,MiddleEast,WestAsia,andAustralia.Sinceitsintroductionin1999intoUSA,thevirushasspreadandisnowwidelyestablishedfromCanadatoVenezuela.Transmissio