John Snow and the Cholera Epidemic: A Landmark in Epidemiology, Medicine and Public Health

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You may have come across the name John Snow, but I'm not referring to your friend or the gun-slinging or Sword wielding actor. This John Snow is renowned for his pivotal role in curbing a cholera outbreak by an act as simple as removing a pump handle. While the story might seem overly straightforward, it's crucial to recount it and then delve deeper into the untold aspects of this event in the realms of medicine and epidemiology.

The story takes us back to 1854 in London's Soho neighborhood, where a devastating cholera outbreak was wreaking havoc, and its cause remained a mystery. As the disease claimed lives, a determined physician named John Snow embarked on a unique investigative journey. He traversed the town, meticulously interviewing residents about their daily activities. Through these interviews, he pieced together a map that unveiled the origin of the cholera outbreak: the water pump on Broad Street. In a bold move, he removed the handle of the pump, and miraculously, the outbreak subsided. It's a heroic tale indeed, and we owe John Snow our gratitude. However, there's more to this story that merits exploration, particularly in the fields of medicine and epidemiology.


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It wasn't like cholera just found its way to London in the 1850s, as far back s in 1831 London had been dealing with cholera which is caused by Vibrio Cholerae. ingesting as little as 10 mllion Vibrio cholerae can get someone sick, and a cup of water can contain about 200 million of it. When a person drinks contaminated water, most of the pathogens die in the stomach thanks to stomach acid but some of them would survive and they will burrow through the layer of the small intestine attaching to small intestine cells and begin to replicate. This leads to abdominal ache as it releases cholera toxin which causes intestinal pain, fever, Cloudy diarrhea know as rice water stool, dehydration, kidney failure, shock and then death. The stool of cholera patients is contaminated with the bacteria, thereby helping it to spread to other people from drinking water.

The disease got to London in 1831 and the health board began to give people different home remedies as well as laudanum which is a combination of Opium and Alcohol. At this point, there was no remedy, but with Laudanum, patients were able to experience reduced diarrhea. At the point, Miasma was still a thing of believe and it was said that it was caused in towns with crowded population, where people didn't pay attention to cleanliness, and ventilation. In Europe, Miasma was the most popular mode of disease cause at the time.


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One figure of note, William Farr, a surgeon working at the office of the registrar general, diligently collected data throughout his career. He categorized people who suffered from cholera and recorded their details based on age, location, occupation, and other factors. His data revealed a clear preference for the disease in densely populated areas with inadequate sanitation. Another individual, Edwin Chadwick, focused on data collection in impoverished neighborhoods, as he believed that poorer areas were less clean and, since diseases were attributed to miasma, their inhabitants were more vulnerable to illness. In 1842, Chadwick published a paper titled "The Report From the Poor Law Commissioner on the Inquiry into the Sanitary Condition of the Labouring Population of Great Britain".

London was very dense as at the time of the disease and Chadwick mentioned that industrialization was part of the reason why the disease was happening in the first instance since it had been having negative impact on the health of the poor than the rich as at the time. He talked about the sewage infrastructure where waste could be going to. While both the industries and humans accepted this, they went about it the wrong way as all their wastes including that of their sewage went to the river Thames and this was the same river were pumps received water from for drinking. He talked about rerouting waste channels so they do not mix with drinking water. This was during the London Cholera epidemic and at this point William Farr wrote a report where he said that the infection of cholera vary inversely with elevation saying people who lived closed to the river were sick with cholera more often than those who lived in hills.


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John Snow challenged Farr's hypothesis as mere coincidental correlation. He argued that, unlike other Miasma-causing diseases, cholera first manifested in the alimentary canal before other symptoms spread in the vicinity of the digestive system. His reasoning was that, since the disease initially affected the gut and was excreted, the cause must have been ingested and excreted through the mouth and anus, respectively

Snow noticed that the south of London had an increased death rate compared other areas, and this people were closer to the polluted areas in the Thames. This led snow to publish his own book titled "On the mode of he Communication of Cholera" although he didn't convince people that the disease was water borne, as he was not able to show proofs.

In 1853, there was another cholera outbreak and this time Snow was able to analyze water from the water pumps in Soho, also he was investigating the water supplying company that supplied those regions where he found that households receiving water from the company that used the dirtier side of the river got cholera. He also went door to door to interview people where he found that people who drank water from the Broad Street pump suffered from cholera. On September 7th 1855 snow was able to discuss with the local parish on removing the head to the pump in Broad Street, and since the death rate was high and there was not really anything to lose, the pump handle was removed on the 8th of September.


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Although the death rate in Soho remained high for a few more days, it gradually began to decline. Yet, the significance of this change largely went unnoticed. However, Henry Whitehead, who was skeptical of Snow's theory, decided to conduct research to challenge the prevailing belief. He was a staunch supporter of the Miasma theory and didn't buy into the notion of contaminated water causing cholera. During his investigation, he discovered a critical piece of evidence – an index case of the disease. It was a baby who had died of cholera, and her diapers had been disposed of in a sewer close to the pump. The sewage from the sewer had been leaking into the pump. To illustrate the sewage contamination theory, John Snow created a map

William Farr also agreed that Snow's hypothesis were correct and agreed that it had changed the way people thought of diseases as Miasma to looking at water contamination as a cause.

The story of John Snow and the Broad Street pump handle is more than just a story of another hero. It represents a pivotal moment in the history of epidemiology, medicine, and public health. Snow's groundbreaking work challenged prevailing beliefs of Miasma, leading to a fundamental shift in how diseases were understood and ultimately paving the way for advancements in disease prevention and control.

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