Disease may be asymptomatic to mild (80 % of cases), severe, or fatal(1,3,5,6,7). Early symptoms include gradual onset of fever, nausea, abdominal pain, severe ...FreeSafetyDataSheetIndexLassavirusLassavirusPATHOGENSAFETYDATASHEET-INFECTIOUSSUBSTANCESSECTIONI-INFECTIOUSAGENTNAME:Lassavirus.SYNONYMORCROSSREFERENCE:Lassafever,Lassafevervirus,viralhaemorrhagicfever(VHF)(1,2,3).CHARACTERISTICS:Double-segmented,single-strandedRNAvirus,belongingtothegenusArenavirus,familyArenaviridae.Theviralfragmentmayoccupyseveraldistinctshapes(pleomorphic)measuring80to150nmindiameter(1,4).ThesurfaceofthevirionlipidenvelopeisstuddedwithglycoproteinsthatconsistoftetramericcomplexesoftheviralglycoproteinsGP1andGP2(4).SECTIONII–HAZARDIDENTIFICATIONPATHOGENICITY/TOXICITY:Acuteviralillnessof1to4weeksduration(3).Diseasemaybeasymptomatictomild(80%ofcases),severe,orfatal(1,3,5,6,7).Earlysymptomsincludegradualonsetoffever,nausea,abdominalpain,severesorethroat,cough,conjunctivitis,ulcerationofbuccalmucosa,exudativepharyngitis,andcervicallymphadenopathy(1,3,5,7,8).Latesymptomsincludesevereswellingofheadandneck,pleuralandpericardialeffusions(8,9).Twenty-fivepercentofcasesresultindeafnessand/or(transient)alopecia(1,3,5,7,10).Thediseaseissevereinpregnancy,resultinginfoetallossin80%ofcases(3,10).DeathasaresultofinfectionwithLassavirusisusuallyduetocardiacarrest(1).Fatalityrateis15to20%ofhospitalizedpatientsand1to2%ofinfectedindividualsingeneral(1,3,7).EPIDEMIOLOGY:EndemicinWestAfrica.Between10,000and300,000infectionsoccurannuallywith5,000deaths(1,3,6,10).OutbreakshaveoccurredinGuinea,Liberia(1972),SierraLeone(1970-72,1973-75,and1996-97),areasofNigeria(firstcasesin1969,furtheroutbreaksin1970,1974,and1975),CentralAfricanRepublic,DemocraticRepublicofCongo,Mali,Senegal,Benin,BurkinaFaso,Cameroon,Ghana,IvoryCoastandSudan(1,3).Approximately20casesofimportedLassafeverhavebeenrecordedworldwide(11,12).HOSTRANGE:Mastomysnatalensis(anAfricanrodentalsoknownasthemultimammatemouseormultimammaterat)andhumans(1,3,4,7