Home/Newsroom/Factsheets/Detail/YellowfeverWHO/E.SoterasJalil©CreditsYellowfever7May2019KeyfactsYellowfeverisanacuteviralhaemorrhagicdiseasetransmittedbyinfectedmosquitoes.The"yellow"inthenamereferstothejaundicethataffectssomepatients.Symptomsofyellowfeverincludefever,headache,jaundice,musclepain,nausea,vomitingandfatigue.Asmallproportionofpatientswhocontractthevirusdevelopseveresymptomsandapproximatelyhalfofthosediewithin7to10days.ThevirusisendemicintropicalareasofAfricaandCentralandSouthAmerica.Largeepidemicsofyellowfeveroccurwheninfectedpeopleintroducethevirusintoheavilypopulatedareaswithhighmosquitodensityandwheremostpeoplehavelittleornoimmunity,duetolackofvaccination.Intheseconditions,infectedmosquitoesoftheAedesaegyptispeciestransmitthevirusfrompersontoperson.Yellowfeverispreventedbyanextremelyeffectivevaccine,whichissafeandaffordable.Asingledoseofyellowfevervaccineissufficienttograntsustainedimmunityandlife-longprotectionagainstyellowfeverdisease.Aboosterdoseofthevaccineisnotneeded.Thevaccineprovideseffectiveimmunitywithin10daysfor80-100%ofpeoplevaccinated,andwithin30daysformorethan99%ofpeoplevaccinated.Goodsupportivetreatmentinhospitalsimprovessurvivalrates.Thereiscurrentlynospecificanti-viraldrugforyellowfever.TheEliminateYellowfeverEpidemics(EYE)Strategylaunchedin2017isanunprecedentedinitiative.Withmorethan50partnersinvolved,theEYEpartnershipsupports40at-riskcountriesinAfricaandtheAmericastoprevent,detect,andrespondtoyellowfeversuspectedcasesandoutbreaks.Thepartnershipaimsatprotectingat-riskpopulations,preventinginternationalspread,andcontainingoutbreaksrapidly.By2026,itisexpectedthatmorethan1billionpeoplewillbeprotectedagainstthedisease. SignsandsymptomsOncecontracted,theyellowfevervirusincubatesinthebodyfor3to6days.Manypeopledonotexperiencesymptoms,butwhenthesedooccur,themostcommonarefever,musclepainwithprominentbackache,headache,lossofappetite,andnauseaorvomiting.Inmostcases,symptomsdisappearafter3to4days.Asmallpercentageofpatients,however,enterasecond,