John Snow- Father of Epidemiology

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When I say the name John Snow, your first thought probably isn’t about cholera. I don’t think there even is cholera in Westeros. Is Winterfell in Westeros? I never got that far into Game Of Thrones. Maybe there’s a whole side plot where Jon Snow discovers that cholera has been killing people this whole time, or maybe that he died of cholera. (I don’t know if that’s a spoiler, because I don’t actually know if he’s dead. I should catch up.) Is there cholera in Game of Thrones? Probably not.

Anyway, the point is that this is not that Jon Snow. This John has an H in his name and was a very real historical figure. Cholera is also very real. Besides being a major plot device in one of my favorite books, Love in the Time of Cholera, it also used to be a big problem. On the Oregon Trail it was devastating and responsible for more deaths than dysentery. 

Cholera originally comes from the Ganges river area in India. The first recorded outbreak was in 1817, which is shockingly recent for a disease. It quickly spread around the world, following trade routes. There have been six major pandemics since then, the latest being in 1961. We’re still technically in this pandemic. The disease is endemic in many parts of the world, especially in developing countries.


Cholera is a diarrheal infection caused by ingesting the bacterium Vibrio cholerae. Most people don’t show symptoms, and if they do, it’s generally mild. But when it’s not it can kill within a few hours of showing symptoms, which can take up to 5 days to appear. Now it is commonly known that the most common way to get the infection is through contaminated water, however that idea was laughed at when it was first proposed by, you guessed it, John Snow.

Snow was finishing up his medical training when the second cholera pandemic hit England in 1832. Nothing he or anyone else did seemed to help the patients, probably because doctors thought that bleeding people was the best way to treat it. It wasn’t. In 1832 the disease disappeared as quickly as it appeared, and Snow was left to ponder what had happened. He had an idea that cholera was passed through dirty water, but that didn’t fit with the idea of disease from the time.

Doctors at the time believed in the miasma idea of disease, where all diseases were created by “bad air”. Just like in Final Fantasy, miasma was seen as a fog that caused destruction wherever it went. Although Snow was taught this is medical school, he didn’t buy it. It didn’t explain why all of the neighbors on one street could get cholera, but none on the street parallel.  

We don’t know exactly how many people died in the third cholera pandemic, but it was probably the most deadly one, taking at least two million lives. England alone lost 23,000 people. Once again, Dr. Snow was on the front lines. From August 31st to September 3rd, 1854, 127 people died of Cholera in Soho, the London suburb where Snow was working. Within a week, that number had jumped to over 500. (Almost) everyone who died lived within 850 feet of a water pump, which Snow though was intriguing to say the least. So he did what any normal person would do; he plotted all the deaths and their home addresses on a map. 

This led him to believe that the Broad Street Pump itself was infected and infected everyone who used its water. This lent credence to his evolving hypothesis that cholera was spread by water. He found more evidence: people who didn’t live in the area but frequented a cafe close to the pump were more likely to die, and people worked in brewery nearby, which had its own pump, were less likely to catch the disease. He took this information to the city council and asked them to remove the pump. They agreed, though no one was convinced it would help.

People in that area stopped getting cholera and dying, although they didn’t think it was due to the removed pump. The next year, Snow and his medical professor found patient zero by finding the earliest case of the disease in the area: an infant who had been brought to the neighborhood, whose diapers had been washed out into a drain a few feet from the Broad Street pump’s water supply. Unfortunately, even though Snow stopped this epidemic, it would be a couple decades before the germ theory of disease caught on. Despite this, Snow’s idea that a disease can be traced to a source through detective work became the foundations for the field of epidemiology.  


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Just a girl who has a lot of feelings about planetary science

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