When Beer is the Answer
One of his most fascinating discoveries was the relative good health of the 535 people who worked in a brewery on Poland Street. Only five of them contracted cholera; probably because they drank water from the Broad Street Pump. According to the foreman, workers were allowed to drink as much of the malt liquor they made as they liked.
It came from water in the brewery’s pump. If they drank water, it would have been from the brewery pump, but according to the foreman, most of the workers didn’t drink water; why would you when you have beer? Snow found that a workhouse on Poland Street was also unaffected. Once again, it has its own water supply. Upon examining the water coming from the pump, Snow found white flecks floating in it which he asserted was the cause of the illness.
Turning the Tide of the Epidemic
By now, Snow had a huge amount of evidence to support his theory that the Broad Street pump was the culprit. He approached the local council and told them to take the handles off the pump to prevent anyone else getting the disease. Although the officials were reluctant to do so as they didn’t believe in Snow’s theory, they acquiesced on a trial basis beginning on September 7. Sure enough, the number of cholera cases dwindled and almost came to a halt within a few months. Residents who had fled Soho slowly returned as the situation improved.
Even though Snow’s plan had the desired effect, his hypothesis was still ridiculed as nonsense. The Board of Health refused to do anything to clean up the cesspools and sewers, and claimed that Snow’s evidence was nothing more than ‘suggestions.’ For his part, Snow continued to track every cholera case for months afterward and found that almost all of them came from the pump at Broad Street. What he couldn’t do was find the source of the contamination. The answer arrived almost by accident.
The Deadly Dirty Diaper
Reverend Henry Whitehead wanted to prove that Snow was wrong and the outbreak was an act of God. Instead, he helped prove Snow’s theory by finding the source of the outbreak. Upon interviewing a woman at 40 Broad Street, Whitehead learned that her child had contracted cholera from a different source. She washed the baby’s dirty diapers in water which was dumped in a cesspool just a few feet from the Broad Street water pump.
In 1855, a magazine called The Builder published Whitehead’s report and called on officials in London to clean up the cesspools and sewers in the city. However, no action was taken for many years. In 1883, a German physician named Robert Koch isolated a bacterium called Vibrio cholerae and determined that cholera wasn’t contagious. Instead, it was transmitted through unsanitary water and food supplies only. It was a victory for Snow in many ways, and once cities in the United States and Europe cleaned up their water supply sanitation, cholera epidemics became a thing of the past.
As for Snow, he died in 1858, long before his work was given due credit. Today, Snow is considered by many to be the world’s first epidemiologist.
Sources For Further Reading:
UCLA – Who First Discovered Vibrio Cholerae?
DW – Robert Koch: The Man and The Microbes
Wired – Sept. 8, 1854: Pump Shutdown Stops London Cholera Outbreak
ThoughtCo – How A Map Stops Cholera
The Guardian – John Snow’s Data Journalism: The Cholera Map That Changed the World