Medicine

The Week Dr. John Snow Saved London (And The Rest Of Us) From Cholera

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Cholera was the great scourge of the 19th century. From 1817 to 1917, more than 40 million people worldwide died from the bacterial infection. One particular outbreak in London's Soho district changed how we fight the disease forever—but not before claiming the lives of more than 500 people in 10 days. At the center of it all was Dr. John Snow, the "father of epidemiology," who prevented an even worse outbreak, but whose ideas wouldn't be fully accepted for nearly 50 years.

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Fighting Illness With Faulty Information

The outbreak of 1854 wasn't the first that Dr. Snow had seen. It wasn't even the first that had made him reconsider the prevailing theory of the time about how disease is spread. According to the theory of miasma, pollutants in the air—such as the odor of sewage or decaying flesh—caused not only cholera, but all diseases. But an outbreak Dr. Snow survived in 1848 and '49 convinced him that the deadly illness was being spread through the water, not the air. When the 1854 epidemic struck, he immediately began plotting the locations of the afflicted and their nearby water sources. When he put his data on a now-famous map, he saw exactly what he was expecting: most of the deaths were clustered around one particular water pump.

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Original map by John Snow showing the clusters of cholera cases in the London epidemic of 1854. The pump is located at the intersection of Broad Street and Cambridge Street (now Lexington Street).

A Solution Borne Out By Research

The Broad Street water pump was the culprit, and the vast majority of cholera deaths were in the buildings immediately surrounding it. Upon investigation, Dr. Snow discovered that of the afflicted who lived farther from pump, half had preferred the Broad Street pump, and another third attended school nearby. This was enough to convince the community to remove the handle from the water pump, and the epidemic was swiftly halted. It wasn't, however, enough to convince his peers of his case, nor was it enough to keep the community from reinstalling the handle shortly after the specter of cholera had passed. Miasma theory wouldn't be fully overturned until approximately 1876, 18 years after Dr. Snow's death.

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Broadwick Street showing the John Snow memorial and public house. The memorial pump was removed due to new construction in March 2016. A plaque affixed to the public house reads, "The Red Granite kerbstone mark is the site of the historic BROAD STREET PUMP associated with Dr. John Snow's discovery in 1854 that cholera is conveyed by water."

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