Lassa virus is a linear, bisegmented, single-stranded RNA virus, which belong to the Arenaviridae family that causes viral hemorrhagic fever transmitted by rats.Openaccesspeer-reviewedchapterAReemergingLassaVirus:AspectsofItsStructure,Replication,PathogenicityandDiagnosisByVictorB.OtiSubmitted:February9th2018Reviewed:May23rd2018Published:November5th2018DOI:10.5772/intechopen.79072Home>Books>CurrentTopicsinTropicalEmergingDiseasesandTravelMedicineAdvertisementDownloaded:1045AdvertisementAbstractLassavirusisalinear,bisegmented,single-strandedRNAvirus,whichbelongtotheArenaviridaefamilythatcausesviralhemorrhagicfevertransmittedbyrats.ThevirusisendemicinWestAfricancountries,whichmaybeduetoitszoonoticnature.LassavirusinfectionoccursthroughcontactwiththevectorMastomysnatalensisorinfectedhumansandcanleadtowidesymptomsfromamildinfectiontoLassafeverandtoaseverefatalviralhemorrhagicfever,whichincludedelayedcellularimmunityresultingtofulminantviremia.ThevirusreplicatesthroughastrategyknownastheAmbisense,wheretwoRNAstrandscodeforgenesinboththesenseandantisensedirectionthatisrapidanddemonstratetemporalcontrolinreplication.Differentdiagnostictestsforthevirusareavailable,whichrangefromviralculturetoserologicalandmoleculardiagnostictests.ThereisanurgentneedtodevelopdrugsandvaccinesagainstthevirusbecausetheWorldHealthOrganization(WHO)hasidentifiedLassavirusasoneofthevirusesthatislikelytocauseafutureepidemic,althougharesearchisongoingtoevaluateLassavirusvaccineimmunogenicityintheCBA/J-ML29mousemodel.Thischaptergivesanoverviewonthestructure,replicationcycle,pathogenesis,anddiagnosisofthevirus.KeywordsLassavirusLassafeverreplicationpathogenesisdiagnosischapterandauthorinfoAuthorVictorB.Oti*DepartmentofMicrobiology,NasarawaStateUniversity,Keffi,Nigeria*Addressallcorrespondenceto:[email protected]:10.5772/intechopen.79072FromtheEditedVolumeIntechOpenCurrentTopicsinTropicalEmergingDiseasesandTravelMedicineEditedbyAlfonsoJ.Rodriguez-MoralesCurrentTopicsinTropicalEmergingDiseasesandT