HEALTH

John Snow and the Broad Street Pump

1854 CE

History · Contemporary · Holocene · Meghalayan

In 1854, John Snow's investigation of a cholera outbreak in Soho, London, established that the disease travelled by water and not by air.

The investigation conducted by John Snow in 1854 into the cholera epidemic in the Soho district of London establishes transmission of the disease by water and not by air. Mapping the deaths around the Broad Street pump does not by itself constitute the demonstration: that rests on the comparison of groups defined by their exposure. Deaths are not distributed by district or by the air breathed, but by the supply pump, and the exceptions confirm the rule, the workers of a nearby brewery who drank beer not having been affected, while a person who had left the district but had that water delivered died at a distance. Snow obtained the removal of the pump handle, a generation before the identification of the germ. Filtration and then chlorination of urban supplies follow several decades later.

Why it matters

Water treatment techniques account for nearly half the total mortality decline recorded in American cities in the early twentieth century and three quarters of the fall in infant mortality, results obtained before medicine had effective treatments for the diseases concerned. The comparative procedure employed by Snow further founds the epidemiological method. The problem remains partly unresolved, insufficient drinking water, sanitation and hygiene still causing about 800,000 annual deaths from diarrhoeal disease, including nearly 300,000 children under five.

Dating & uncertainty

The date retained is that of the 1854 investigation, which founds the discipline but does not correspond to the measurable health effect, which results from the filtration and chlorination implemented several decades later.

Our species’ history as one day

23:59:1247.2 s before midnight

if the 315,000 years of Homo sapiens were compressed into a single day