Revolutions in Epidemiology: Snow Map of Cholera
John Snow was born in 1813 at York, England. He is known for his remarkable work in the field of anesthesia on ether and chloroform, as well as in the field of epidemiology for his work on cholera on which he also published his book “mode of communication of cholera” and wrote 16 papers on prevention of Cholera. He was the pioneer of obstetric anesthesia and known for administering chloroform to Queen Victoria during her delivery.
Snow proposed that “Cholera is a water-borne communicable disease”. His theory gained importance when in 1848, pandemic of cholera reached London from Asia. In mid 1800s it was considered that cholera was air born infectious disease and occurs due to “miasma” (pollution or bad air). Snow, on his knowledge of anesthetic gases denied the hypothesis that if it was true than the workers involved in offensive trades would have suffered more but that was not true.
Snow reached to the conclusion that cholera was transmitted by the ingestion of “morbid matter”. This theory was not accepted until 1854, when an outbreak of cholera attacked Soho section of London. Snow proposed that people who drink water from water pump on Broad street in Golden Square were more affected. He interviewed all the residents of Broad Street who complained of unpleasant odour of water.
He reviewed the records and came to know that 500 cholera cases were reported in three days and total number of deaths reached 616 around the vicinity of Broad street. A lady in the Hampstead who had belief that water from Broad street pump is superior and used to drink water from there, died. Snow plotted the deaths due to cholera on a dot map in the vicinity of Broad street and presented his findings in front of Board of Governors who ordered for the removal of pump handle and so the epidemic abated. Snow proposed that a sewer from Marshall street passes below the pump which was responsible for the contamination of water.
This map changed the perspective of data visualization. Cholera endemic of 1848 and presentation of map at that time make us think about how a map brought attraction towards cholera theory of being transmitted by water. Long charts and data as well as their interpretation sometimes could not convince as maps or diagrams that make conclusion easy.
1. Thomas KB. John Snow, 1813-1858. J Roy Coll Gen Practit 1968; 16:85.
2. Ramsay MAE. John Snow, MD: anaesthetist to the Queen of England and pioneer epidemiologist. Proc (BaylUniv Med Cent) 2006; 19: 24–28.
3. Brody H, Rip MR, Vinten-Johansen P, Paneth N, Rachman S. Map-making and myth-making in Broad Street: the London cholera epidemic, 1854.Lancet 2000; 356: 64–68
4. McLeod KS. Our sense of Snow: the myth of John Snow in medical geography. Social Science & Medicine 2000; 50(7-8): 923-35.
About the Author: Feriha Fatima graduated from LUMHS, Pakistan, in 2007. She is working as a lecturer in biochemistry department since 2010. Feriha is interested in research especially in field of molecular biology and human genetics and can be reached at [email protected]
About this article: This article is competing for the JPMS International Medical Writing Contest 2013
To learn more about the contest and to participate in it, follow this link: http://blogs.jpmsonline.com/writing-contest/
To support the author win this contest, share and like this article at different social media platform using the social icons given in this page. Please note the rules and regulations for this contest for details.
Join JPMS Medical Blogs Team as Editor or Contributor, email your cover letter and resume to [email protected]e.com
We welcome Guest posts. Submit online via: http://blogs.jpmsonline.com/submit/
Disclaimer: JPMS Medical Blogs are published by the same publisher of Journal of Pakistan Medical Students (JPMS). This article does not reflect the policies of JPMS or its Staff or Editorial nor it intends to provide legal, financial or medical advice. Refer to Disclaimer and Policies section for more details.
Advertisement: Call for Papers for Journal of Pakistan Medical Students (www.jpmsonline.com): Submit Original Article, Review Article, Case Report, Letter to the Editor, News Article, Clinical Images, Perspectives or Elective Report to JPMS. We also publish Conference Proceedings and Conference Abstracts as Supplement. No paper submission or publication charges. Submit your articles online (click here) or send it as an Email to: [email protected] and Causes