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Father of Modern Epidemiology: John Snow

John Snow "Father of Modern Epidemiology"
John Snow "Father of Modern Epidemiology"

John Snow, born in 1813, was the son of a coal-yard laborer in York, England. Snow planned to become a physician, and at fourteen, he was apprenticed to Dr. William Hardcastle. During his early years as an apprentice, he filled notebooks with his thoughts and observations on scientific subjects. In the summer of 1831, when Snow was eighteen and in his fourth year as an apprentice, an epidemic of cholera struck London. The disease, which had already killed hundreds of thousands of people on the European continent, spread north to Newcastle in October. The first symptom of cholera was queasiness, followed by stomachache, vomiting, and diarrhea so profuse that it caused victims to die of dehydration.

Dr. Hardcastle had so many sick patients that he could not personally see them all, so he sent Snow to treat the many coal miners who had fallen sick at the Killingworth Colliery. There was little that Snow could do to help the stricken miners, because the usual treatments for disease- bleeding, laxatives, opium, peppermint, and brandy -- were ineffective against cholera. Snow continued to treat cholera patients until February of 1832, when the epidemic ended as suddenly and mysteriously as it had begun. By that time, it had left fifty thousand people dead in Great Britain.

During the next sixteen years, Snow earned an M.D. degree, moved to London, became a practicing physician, and distinguished himself by making the first scientific studies of the effects of anesthetics. By testing the effects of precisely controlled doses of ether and chloroform on many species of animals, as well as on human surgery patients, Snow made the use of those drugs safer and more effective. Surgeons who wished to anesthetize their patients no longer risked killing them by the unscientific application of chloroform-soaked handkerchiefs to their faces.

Snow began to do a lot of thinking about the possible causes of contagious diseases, and he came to the unconventional conclusion that they might be caused by invisibly tiny parasites. This was not an original idea, but it was an unpopular one during the first half of the nineteenth century. The "germ theory" of disease had first been proposed in ancient times, and the discovery of microscopic organisms in the late 1600s had made the theory seem plausible, but no one had ever proved that miniature organisms could make people sick.

In Snow's day most physicians believed that cholera was caused by "miasmas" -- poisonous gases that were thought to arise from sewers, swamps, garbage pits, open graves, and other foul-smelling sites of organic decay. Snow felt that the miasma theory could not explain the spread of certain diseases, including cholera. During the outbreak of 1831, he had noticed that many miners were struck with the disease while working deep underground, where there were no sewers or swamps. It seemed most likely to Snow that the cholera had been spread by invisible germs on the hands of the miners, who had no water for hand-washing when they were underground.

Title page of Snow's pamphlet

In August of 1849, during the second year of the epidemic, Snow felt obliged to share what he considered convincing evidence that cholera was being spread through contaminated water. At his own expense he published a pamphlet entitled On the Mode of Communication of Cholera. Thirty-nine pages in length, the essay contained both a reasoned argument and documentary evidence to support his theory. As one example he cited the case of two rows of houses in a London neighborhood that faced each other. In one row many residents became cholera victims, while in the other row only one person was afflicted. It was discovered, Snow wrote, that "in the former bowl the slops of dirty water, poured down by the inhabitants into a channel in front of the houses, got into the well from which they obtained their water." Snow realized that such conditions existed in many neighborhoods and that if cholera epidemics were ever going to be eliminated, wells and water pipes would have to be kept isolated from drains, cesspools, and sewers.

Snow's research remains extremely relevant today, necessitating sanitary septic infrastructure in any populated area. The pathogen Vibrio cholerae is not contagious from body to body but is easily spread through food and water sources that become contaminated with sewage. The conditions necessary to induce a cholera outbreak still exist in many countries where hygienic water sources are not readily available. The largest outbreak in modern history occurred months after the 2010 Haitian earthquake. 6,631 deaths were recorded among the 470,000+ reported cases. The Centers for Disease Control and Prevention (CDC) soon went to work, establishing guidelines for cholera treatment and avoidance as well as setting up sanitation facilities. $75 million has been spent by the US government in attempts to control the disease but Haiti will likely continue to have increased cholera transmissions far into the future. Educating people in hygienic practices can only go so far. Efficient water and sewage infrastructure is vital to reducing the impact of the disease. John Snow was the first to recognize the importance of a clean water supply after investigating the cholera outbreaks of 1800s London. His work was the first step into requiring strict government and city maintenance of water resource structures.




Father of Epidemiology

Haitian Cholera Outbreak

6 thoughts on “Father of Modern Epidemiology: John Snow

  1. Justin Ferguson

    Very interestng article, I had no idea who was the starter of the sanitary water system we all love. I say sanitary in a slightly sarcastic tone, not sure how clean tuscaloosa's water is. It is sad that other countries don't have the ability to have access to acceptably clean water despite efforts from other countries to help. Overall great read, I was very interested in his work.

  2. Patrice

    This is interesting. With so much technology and protocols, I think it's easy for us to overlook how profound a breakthrough sanitation systems truly were and how complicated establishing a good system can be. Prior to the earthquake, Haiti was not having a cholera outbreak. There's such a thin line. If we are too aggressive with sanitation (like sanitizing everything all the time), then only the "super germs" are able to grow and wreak havic. If there is too little sanitation in place, then other diseases and germs may attack. So quickly our happy balances can crumble.

  3. Emily Hoskins

    I remember in middle school when talking about the plague we talked a lot about the sanitary conditions of the cities. There was no plumbing, bodies were on the sides of the street, and other factors. I remember hearing about the "miasmas" hypothesis but never heard the name of the hypothesis or about the person who came up with it. I realized reading the article and the blogpost that I knew a little more about epidemiology and the "miasmas" hypothesis. It was a very interesting blogpost and I always enjoying hearing new findings on diseases.

  4. aeschmitt

    I found this blogpost and the Human Biology textbook chapter held some of the most interesting topics regarding human biology. To us, it seems obvious that clean water and good hygiene are extremely important in preventing disease, and it blows my mind to remember that this knowledge has not always been available. It also makes me wonder about some of the theories behind over-sanitation and the rise of "super-bugs". Because we are so particular about washing our hands, using hand sanitizer, and other methods of trying to stay as germ-free as possible, some scientist believe that we have thus weekend our own immune systems and have created these super-bugs - as in, the only germs left are the very dangerous ones that have survived our over-sanitation efforts. It would be very interesting to study whether or not this is true and that staying "too clean" has actually hurt us in the long run.

  5. ajcallery

    I think this chapter was really interesting and relevant to the whole Ebola scare that is being created by the media. If the media used the different models of how diseases and viruses spread I believe that it would not be as much of a scare behind Ebola in America. Americans would see that the person has to be having symptoms of the disease to pass it on and then that person has to come in contact with fluids of some sort from the infected person. I also think that the 3 cases that are being presented to the public are overshadowing other issues that are brought up in the book, such as the continuation of tuberculosis in a now resistant strain. The strain is resistant to our original drugs used to treat it and results in longer and more expensive treatments of the disease, which results in even more resistant forms of the disease when one does not finish the treatment regimen.
    I really like how in depth the chapter got with the terms, the different models, and what can go wrong with doing these studies. The use of anthropology and public health to help with the epidemiological significance and how to prevent and stop the spreading helps to highlight the interdisciplinary work that is often needed. All of the examples are interesting. The example of how John Snow was able to find the source of the spread of cholera shows how early on these connections can be made without the use of all the technology we have currently. The break down of the different ways that epidemiologist do research was insightful to how certain research designs are more helpful in certain areas. The potential problems section was helpful in making sure one looks at these epidemiological studies with a critical eye to ensure that there was not bias or confounding variable that altered the results.
    I decided to look up an article on a disease that I believe is more of a concern to American’s, tuberculosis. The article titled Extensively drug-resistant tuberculosis (XDR-TB) among health care workers in South Africa. The connection between XDR-TB and healthcare workers is one that can be related to the occurrences of Ebola among Americans, mostly healthcare workers of some sort are the ones who have gotten the disease. The difference we see with XDR-TB and Ebola is that XDR-TB is a lot easier to transmit to others. In Africa, the resurgence of XDR-TB has been able to spread due to the high amount of individuals who have HIV/AIDS, which makes one more susceptible to diseases like TB. The main problem with the health care workers and the existence of XDR-TB is that there are 3% of the world’s health care workers and 24% of the world burden of disease. This means overworking and more patients per worker, increasing the probability of being exposed. The other problem is that when a healthcare worker does catch TB, any strain of it, they are out of commission for a while to recover and prevent further spread to patients, coworkers, and family.
    In the article, they looked at patients in Eastern and Western Cape Provinces of South Africa from 1996-2008 that had been diagnosed with XDR-TB and observed if they were health care workers. Out of the 334 people who contracted the disease, 10 were health care workers. These were mostly females and the majority was nursing staff. Four out of the ten people died from the disease. This study shows how important it is to keep the health care workers healthy and ensuring that the protocol and treatment of sick patients should be done in a fashion that allows the disease little ability to be passed on to health care workers. With the shortage of healthcare worker that South Africa already has, better protocol needs to be used to ensure that they are even less healthcare workers to help the sick. With the sample population being so small it is hard to make any definitive conclusions about the connection of HIV/AIDS and XDR-TB, but upon looking at the breakdown of the healthcare workers only 2 of the 10 were positive for HIV. This shows that the assumed connection between XDR-TB and HIV is not always necessary for an individual to contract the disease.

    Jarand, J., Shean, K., O’Donnell, M., Loveday, M., Kvasnovsky, C., Van der Walt, M., Adams, S., Willcox, P., O’Grady, J., Zumla, A., Dheda, K. (2010). Extensively drug-resistant tuberculosis (XDR-TB) among health care workers in South Africa. Tropical Medicine and International Health, 15: 1179-1184.

  6. Laura Hurter Chandler

    This was an interesting read and also enjoyed the class activity. We take for granted our sanitation, so it was nice to see where things were started. And to also hear stories of what it was like before proper sanitation. It's hard to believe that there are still places in the world that struggle with this, as well. There are still many countries that have a large amount of deaths because of a lack of sanitary facilities. It is second nature to us now to wash our hands. It's hard to imagine a time where that wasn't common sense to people.

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