The Lassa virus particle is round, oval, or pleomorphic, 110 to 130 nm in diameter, and enveloped. Its genome consists of two single-stranded RNA segment – the large L segment and the small S segment.SkiptomaincontentCloseSearchMenuLASSAEBOLALassaLassafever(Lassa)isanacuteviralhemorrhagicfeverendemictoWestAfrica.Sinceitsdiscoveryin1969inthevillageofLassainBornoState,Nigeria,therehavebeencountlessoutbreaksofvariousmagnitudeandseverityacrossWestAfrica.Itisestimatedthatmanythousandsofpeopleareinfectedwiththevirusannually,withthousandsofdeaths.Casefatalityratesininfectedpatientscanreachmorethan80%.Thesenumbers,however,areonlyestimates,andinrealitylittleisknownaboutthetruemorbidityandmortalityfromthisdisease.GeographicalDistributionLassaisendemictoWestAfrica.ConfirmedincidenceshavebeenrecordedinSierraLeone,Liberia,Guinea,Nigeria,IvoryCoast,Togo,andMali.However,concernsexistthattheremaybeLassa(andLassa-like)virusesinothercountriessuchasCentralAfricanRepublic,BurkinaFaso,Ghana,Benin,andCameroon–someofwhichhavehadsporadiccases.Furthermore,MastomysrodentsaredistributedacrosstheAfricancontinent,indicatingastrongpossibilityforthespreadofthediseases,includingLassa,thattheycarry.InfectionswithLassavirusHumanscontractthevirusprimarilythroughcontactwiththecontaminatedexcretaofMastomysnatalensisrodents(commonlyknownastheMultimammaterat),whichisthenaturalreservoirforthevirus.Littleisknownregardingthetransmissionofthevirusfromtherodentreservoirtothehumanhost,althoughthereiscompellingevidencethatArenavirusesarestableandinfectiousbytheaerosolrouteinnonhumanprimates.Therodentsliveinhouseswithhumansanddepositexcretaonfloors,tables,bedsandfood.Consequentlythevirusistransmittedtohumansthroughcutsandscratches,orinhaledviadustparticlesintheair.InsomeregionsMastomysrodentsarealsoconsumedasfood.Secondaryhuman-to-humantransmissionscanalsooccur,althoughsuchscenariosaremuchrarerthanrodent-causedinfections.Historically,small-scaleoutbreakscausedbyhuman-to-humantransmissionshavetakenplace,butmostly