Source: UCLA
Published: November 2013

John Snow and the Broad Street Pump (1854)

Circulated: September 6, 2019

Cholera is a bacterial disease causing severe diarrhea and dehydration. Between 1831 and 1854, tens of thousands of people in England died of cholera. At the time, the way that cholera spread was a mystery, generally attributed to bad air.

In 1854 Soho, a suburb of London, was hit hard by an outbreak of cholera. Dr. John Snow who specialized in pregnancy and childbirth believed water or food was the true cause of the outbreak. To prove his hypothesis, he plotted cases of cholera on a map of Soho and was able to identify a water pump in Broad Street as the source of the disease.

Dr. Snow had the pump handle removed, and cases of cholera immediately began to diminish. Researchers later discovered that this public well had been dug 3 feet from an old cesspit, which had begun to leak fecal bacteria.

This is a powerful application of data used to save lives.