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1、JohnSnowandtheBroadStreetCholeraOutbreakof1854CholerareachedtheBritishIslesintheearly1830s,andoutbreakswouldcontinueforthenextfiftyyears.Today,itiswellknownthatcholeraiscausedbythebacteriaVibriacholeraeandisusuallyspreadinpoordrinkingwater.Earlytheoriesbl
2、amedtheinfectiononmistsand'miasmas',whichledtomanyoftheearlyattemptstocontrolcholerafailing.Inrealitythepoorsanitaryconditionsofacity'swatersupplywasresponsible.EarlyVictoriancitiesalsoincludedcowshedsmixedinamongstthehouses.Thesecombinedwithpoorhandlingo
3、fhumansewage(oftenmerelyaholeintheground)ledtoarapidcontaminationofthedrinkingwater.Indeed,thefamousBroadStreetwaterpump(seebelow)wasashallowwaterpumpthatpumpedwaterfromthecontaminatedwatertable.Inthe1850s,JohnSnowperformedpioneeringdataanalysistoprovehis
4、hypothesisthatcholerawasspreadinthedrinkingwater.Thisanalysisifperformedtoday,wouldcomeundertherealmsofGIS(GeographicInformationSystems)andDataMining.SomehaveclaimedhisBroadStreetmapasbeingthefirstexampleofGIS,eventhoughitwasperformedwithapenandpaper.Alth
5、oughthisisanexaggeration,theBroadStreetmapitisanexcellentexampleofthepowerofmapstoclearlydemonstraterelationshipsincomplexscenarios.Snow'sworkwiththeLondoncholeraoutbreaksofthe1850s,isoftencitedasthebeginningofmodernepidemiology.Unfortunatelywordofthispio
6、neeringepidemiologywasslowtospread,andtheLondoncholeraoutbreakswouldcontinueintothe1880swhenalloftheshallowwater-pumpswerefinallydecommissioned.ThispagelooksatSnow'stwomostfamousanalysiscasesthathelpedtoprovehishypothesisthatcholerainfectionsoccurredthrou
7、ghdrinkingwater.TheBroadStreetOutbreak,1854ThisisthemostfamouspieceofdataanalysisperformedbyJohnSnow,andhispromptactionundoubtedlysavedmanylives.TheoutbreakoccurredintheSohoDistrictofLondon,inandaroundBroadStreet.JohnSnowreasonedthatifcholerawasspreadbyam
8、istormiasma,astheprevailingtheoriessuggested,thenthecasesshouldbeuniformlydistributedalongthestreets.Toseeifthiswasthecase,heplottedeachcholeracaseonamap,similartotheoneontheleft.Healsoplottedhouseswithmultiplecases