Rubuta ci gaba don wannan sakin layi - Nazarin da John Snow yayi game da barkewar cutar kwalara a London
ana daukar shi a matsayin binciken muhalli na farko don magance matsalar kiwon lafiya. Ya yi amfani da taswirar mutuwar da cutar kwalara ta yi don sanin cewa tushen cutar kwalara famfo ne a kan Broad Street. Ya cire makullin famfo a shekara ta 1854 kuma mutane sun daina mutuwa a can. Sai da Robert Koch ya gano ƙwayoyin cuta bayan shekaru da yawa ne aka fahimci yadda cutar kwalara take yaɗuwa.