Kammala wannan jumla: Daya daga cikin sanannun gwaje-gwaje na farko na halitta shine
1854 Cutar cutar kwalara ta Broad Street a Landan, Ingila. A ranar 31 ga Agusta, 1854, wata babbar cutar kwalara ta afkawa Soho. A cikin kwanaki uku masu zuwa, mutane 127 kusa da Broad Street suka mutu. A karshen barkewar cutar mutane 616 suka mutu. Likita John Snow ya gano asalin barkewar cutar a matsayin famfo na ruwa mafi kusa, ta amfani da taswirar mutuwa da rashin lafiya wanda ya nuna tarin lamura a kusa da famfo.