Ka kammala wannan magana: A wannan shekarar, likitan Biritaniya John Snow, wanda yake aiki a wani yanki da ake talauci a Landan, ya gano cewa gurɓataccen ruwa ne yake yaɗawa da cutar. Bayan da
1854 Cutar cutar kwalara ta Broad Street ya zana taswirar cutar kwalara a yankin Soho a London, kuma ya lura da tarin cututtukan kusa da famfon ruwa a wani unguwa. Don ya gwada ra'ayinsa, ya rinjayi ma'aikatan gwamnati su cire makullin famfo, kuma adadin masu cutar kwalara a yankin ya ragu nan da nan. Binciken da ya yi ya sa aka shawo kan annobar. Snow ya kasance memba mai kafa kungiyar Epidemiological Society of London, wanda aka kafa a sakamakon barkewar cutar kwalara a 1849, kuma ana daukarsa daya daga cikin iyayen cututtukan cututtukan cututtukan cututtukan cututtukan cututtukan cututtukan cututtuka.