In the early- to mid-19th century, cholera tore through England, killing tens of thousands. The prevailing scientific theory of the day said that the disease was spread by foul air known as a “miasma.”
But a British doctor named John Snow suspected that the mysterious disease, which killed its victims within days of the first symptoms, lurked in London’s drinking water.
Snow acted like a scientific Sherlock Holmes, investigating hospital records and morgue reports to track the precise locations of deadly outbreaks. He created a geographic chart of cholera deaths over a 10-day period and found a cluster of 500 fatal infections surrounding the Broad Street pump, a popular city well for drinking water.
“As soon as I became acquainted with the situation and extent of this irruption (sic) of cholera, I suspected some contamination of the water of the much-frequented street-pump in Broad Street,” wrote Snow.
With dogged effort, Snow convinced local officials to remove the pump handle on the Broad Street drinking well, rendering it unusable, and like magic the infections dried up. Snow’s work didn’t cure cholera overnight, but it eventually led to a global effort to improve urban sanitation and protect drinking water from contamination.
While cholera has largely been eradicated in developed countries, it’s still a persistent killer in third-world countries lacking adequate sewage treatment and access to clean drinking water.