Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. For the majority of Lassa fever ...SkipdirectlytositecontentSkipdirectlytopageoptionsSkipdirectlytoA-ZlinkSkipdirectlytoA-ZlinkSkipdirectlytoA-ZlinkLassaFeverSectionNavigationCDCHomeFacebookTwitterLinkedInSyndicateSignsandSymptomsFrenchMinusRelatedPagesSignsandsymptomsofLassafevertypicallyoccur1-3weeksafterthepatientcomesintocontactwiththevirus.ForthemajorityofLassafevervirusinfections(approximately80%),symptomsaremildandareundiagnosed.Mildsymptomsincludeslightfever,generalmalaiseandweakness,andheadache.In20%ofinfectedindividuals,however,diseasemayprogresstomoreserioussymptomsincludinghemorrhaging(ingums,eyes,ornose,asexamples),respiratorydistress,repeatedvomiting,facialswelling,paininthechest,back,andabdomen,andshock.Neurologicalproblemshavealsobeendescribed,includinghearingloss,tremors,andencephalitis.Deathmayoccurwithintwoweeksaftersymptomonsetduetomulti-organfailure.ThemostcommoncomplicationofLassafeverisdeafness.Variousdegreesofdeafnessoccurinapproximatelyone-thirdofinfections,andinmanycaseshearinglossispermanent.Asfarasisknown,severityofthediseasedoesnotaffectthiscomplication:deafnessmaydevelopinmildaswellasinseverecases.Approximately15%-20%ofpatientshospitalizedforLassafeverdiefromtheillness.However,only1%ofallLassavirusinfectionsresultindeath.Thedeathratesforwomeninthethirdtrimesterofpregnancyareparticularlyhigh.Spontaneousabortionisaseriouscomplicationofinfectionwithanestimated95%mortalityinfetusesofinfectedpregnantmothers.BecausethesymptomsofLassafeveraresovariedandnonspecific,clinicaldiagnosisisoftendifficult.Lassafeverisalsoassociatedwithoccasionalepidemics,duringwhichthecase-fatalityratecanreach50%inhospitalizedpatients.Pagelastreviewed:March25,2014Contentsource:CentersforDiseaseControlandPrevention,NationalCenterforEmergingandZoonoticInfectiousDiseases(NCEZID),DivisionofHigh-ConsequencePathogensandPathology(DHCPP),ViralSpecialPathogensBranch