Denguevirusisasingle-strandedRNAvirusofabout50nmindiameterbelongingtothegenusFlavivirus.Dengueanddenguehemorrhagicfeverarecausedbyoneoffourcloselyrelated,butantigenicallydistinct,virusSEROtypes(DEN-1,DEN-2,DEN-3,andDEN-4).Infectionwithoneoftheseserotypesdoesnotprovidecrossprotectiveimmunity,sopersonslivinginadengue-endemicareacanhavefourdengueinfectionsduringtheirlifetimes.ThevirusesaretransmittedbyAedesaegypti,adomestic,day-bitingmosquitothatpreferstofeedonhumans.Infectionwithdenguevirusesproducesaspectrumofclinicalillnessrangingfromanonspecificviralsyndrometosevereandfatalhemorrhagicdisease.Itisprimarilyadiseaseofthetropics;itsglobaldistributioniscomparabletothatofmalaria,andanestimated2.5billionpeopleliveinareasatriskforepidemictransmission.Globally,thereareanestimated50to100millioncasesofdenguefeverandseveralhundredthousandcasesofdenguehemorrhagicfever.Thecase-fatalityrateofDHFinmostcountriesisabout5%;mostfatalcasesareamongchildrenandyoungadults.ImportantriskfactorsforDHFincludethestrainandserotypeoftheinfectingvirusaswellastheage,immunestatusandgeneticpredispositionofthepatient.Riskgroupsareresidentsoforvisitorstotropicalurbanareas.Thepresenceofvirusresp.infectionmaybeidentifiedbyserology(detectionofantibodiesbyELISA).Infectionproduceslifelongimmunity,buttheantigenicallydistinctserotypesdonotprovidecross-protectiveimmunity,soapersoncantheoreticallyexperiencefourdengueinfections;adenguevaccineisnotavailable.