John Snow and the Birth of Epidemiology

What happened

When a violent cholera outbreak killed hundreds in London's Soho in 1854, the physician John Snow mapped the deaths and traced nearly all of them to a single public water pump on Broad Street. Persuading officials to remove the pump handle, he helped end the outbreak — and made his case that cholera spread through contaminated water, not 'bad air.'

Why it matters

Snow's Broad Street investigation is celebrated as the birth of modern epidemiology — the science of tracking disease through populations — and a foundation of evidence-based public health.

Sources

• AJR / U.S. National Library of Medicine (PMC). John Snow, Cholera, the Broad Street Pump; Waterborne Diseases Then and Now · Peer-reviewed