West Nile virus (WNV) is an infectious disease that first appeared in the United States in 1999. Infected mosquitoes spread the virus that ...YouAreHere:Home→HealthTopics→WestNileVirusURLofthispage:https://medlineplus.gov/westnilevirus.htmlWestNileVirusAlsocalled:WNVOnthispageBasicsSummaryStartHereSymptomsPreventionandRiskFactorsLearnMoreRelatedIssuesSee,PlayandLearnNolinksavailableResearchStatisticsandResearchJournalArticlesResourcesFindanExpertForYouPatientHandoutsSummaryWestNilevirus(WNV)isaninfectiousdiseasethatfirstappearedintheUnitedStatesin1999.Infectedmosquitoesspreadthevirusthatcausesit.PeoplewhogetWNVusuallyhavenosymptomsormildsymptoms.Thesymptomsincludeafever,headache,bodyaches,skinrash,andswollenlymphglands.Theycanlastafewdaystoseveralweeks,andusuallygoawayontheirown.IfWestNilevirusentersthebrain,however,itcanbelife-threatening.Itmaycauseinflammationofthebrain,calledencephalitis,orinflammationofthetissuethatsurroundsthebrainandspinalcord,calledmeningitis.Aphysicalexam,medicalhistory,andlaboratorytestscandiagnoseit.Olderpeopleandthosewithweakenedimmunesystemsaremostatrisk.TherearenospecificvaccinesortreatmentsforhumanWNVdisease.ThebestwaytoavoidWNVistopreventmosquitobites:UseinsectrepellentGetridofmosquitobreedingsitesbyemptyingstandingwaterfromflowerpots,bucketsorbarrelsStayindoorsbetweenduskanddawn,whenmosquitoesaremostactiveUsescreensonwindowstokeepmosquitoesoutStartHereFAQ:GeneralQuestionsaboutWestNileVirus(CentersforDiseaseControlandPrevention)WestNileVirus(AmericanAcademyofFamilyPhysicians)AlsoinSpanishWestNileVirus(NationalInstituteofAllergyandInfectiousDiseases)SymptomsWestNileVirus:SymptomsandTreatment(CentersforDiseaseControlandPrevention)AlsoinSpanishPreventionandRiskFactorsFindtheRepellentthatisRightforYou(EnvironmentalProtectionAgency)PreventionofWestNileVirus(CentersforDiseaseControlandPrevention)AlsoinSpanishRelatedIssuesFAQ:WestNileVirusandDeadBirds(CentersforDiseaseControlandPrevention)StatisticsandResearchStudyofMosquitoProteinCouldLeadt