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Fig.l PhotographoftypestrainofL.pneumophilaserogroup133152
reportedLegionelapneumoniacaseshassinceincreaseddramaticaly:56casesin19， 281casesin2005，and892casesin2008(3).In2002，anoutbreakofLegionelosisoccun・ed at apublic bathouse in Miyazaki，Japan. In the outbreak，32 cases were laboratory confirmedasLegionelapneumoniaand263casesweresuspectedtobeso.Meanwhile， KoreaCentersforDiseaseControlandPreventionreceivedtherepQrtsof6casesin195， 24casesin2009(4).AlthoughlegionelosisinKoreaislesthanone-tenthofthatinJapan，it issteadilyincreasing.Legionelasp.isaubiquitousintracelularmicrorganismpresentin naturalandmanmadeaquaticenvironments(5)ー(7). Figure2showsLegionel lainfectionpath to human 1ung. The bacteria proliferate in stagnant warm water，as found in co oling towers(8)ラ evaporative condensers of1arge air.圃 conditioning systems，plumbing systems， showers，whir句01spas，denta1c1inicsetings，andsimi1ardiseminators(9). Legionaires' diseaseisinfectedbyinhalingsmaldropletsofwatersuspendedintheair，whichcontain theLegionelabacteria(10). Legionelaehard1ygrowattemperaturesbelow200Corabove 500Candareeasilykiledattemperaturesabove60oC.E1evatedwatertemperatureisoneof themethodsusedtoeradicateLegionelafi.omwatersystems.Inhospita1orpublicwater systems，Legionelaecanbekiledbyraisingthetemperatureofthehotwatersuplyto70 t o 8 0 0 C ( 1 1 ) ( 1 2 ) . J a p a n e s e g u i d e l i n e s f o r 戸p 1 thetemperatureofwater坑stor‘ed泊inhotandwarmwater可sys坑temsmustbemaintainedata minimumof60oC.
ItisreportedthatLegionelasp.cansurviveinsidebiofilmsunderhightemperatureof aproximately700C andhighchlorinationof50mgL-1(13). Biofilmsarecomposedof mineralpartic1es，avarietyofmicrorganisms，andanetworkofslime，orglycocalyx，that bindsthemicrorganismsandpatic1estogether(14)(15). Biofilmsexist.whereversurfaces contactwater.Thesurfacecolonizationcantakeplaceeitheronthesolid-liquidinterfaceor ontheair-liquidinterface.HighconcentrationsofLegionelaearegeneralyasociatedwith the proliferation of host protozoa in biofilms. Fre e-living protozoa，e.g amoeba，may enhancethemultiplicationofbacteria，serveasatransmisionvector，orserveasashelter againstunfavorableenvironmenta1conditions，suchasthepresenceofdisin
Lifecycle0'1Legionelαinaquaticenvironments [nfectiousparticJesare Legionelaenlerlhehumanhost aerosolizedanddispersed byinhalationofinfectiousparticlcs
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Fig.2 Legionelainfectionpathtohumanlung
Vo.l6，No.3，201
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