West Nile virus (WNV) is a mosquito-carried virus that can cause illness ranging from a mild fever to more serious disease like encephalitis or meningitis.Thispage,WestNileVirus(WNV),ispartofMosquito-borneDiseasesshowmoreFactSheetsonInfectiousDiseasesThispage,WestNileVirus(WNV),isofferedbyBureauofInfectiousDiseaseandLaboratorySciencesshowmoreDepartmentofPublicHealthWestNileVirus(WNV)FactsheetaboutWestNileVirusWhatisWestNileVirus?WestNilevirus(WNV)isamosquito-carriedvirusthatcancauseillnessrangingfromamildfevertomoreseriousdiseaselikeencephalitisormeningitis. ItwasfirstidentifiedintheUnitedStatesin1999.HowisWNVspread?WNVismostcommonlyspreadtopeoplethroughthebiteofaninfectedmosquito. MoreinformationaboutdifferenttypesofmosquitoesthatcanspreadWNVcanbefoundontheMDPHwebsiteatwww.mass.gov/dph/mosquito.WNVmayalsobespreadthroughbloodtransfusionororgantransplant. Inaddition,therearerarereportsofWNVbeingpassedfrompregnantorbreastfeedingwomen,whoareinfectedwithWNV,totheirbabies. Sincethesereportsarerare,thehealtheffectsonanunbornorbreastfeedingbabyareunclearandstillbeingstudied.Peopledonotbecomeinfectedbyhavingdirectcontactwithotherinfectedpeople,birdsoranimals. Whydon’tIneedtoreportdeadbirdsanymore?From2000to2008,MDPHcollectedreportsandrantestsforWNVondeadbirdsinMassachusettsasoneofseveralwaystomonitorWNVactivityacrossthestate. Inrecentyears,thismethodhasbecomelessusefulforfindingthevirus. Manyotherstateshavediscontinueddeadbirdreportingandtesting. MosquitocollectionandtestinggivesthemostreliableindicationofcurrentWNVactivityandthisiswheremonitoringactivitieswillcontinuetobefocused.DeadbirdsarenolongerbeingtestedforWNVanddonotneedtobereportedtoMDPH. Deadbirdscanbesafelydisposedofinthetrash. Usinggloves,ashovelorplasticbagscoveringyourhands,thedeadbirdshouldbedouble-baggedandplacedinthetrash. Youshouldthenwashyourhands.WhatarethesymptomsofWNV?ThemajorityofpeoplewhoareinfectedwithWNV(approximately80%)willhavenosymptoms.Asmallernumberofpeoplewhobecomeinfected(~20%)willhavesympto