Wednesday, February 1, 2017

Map Making and Myth Making in Broad Street: The London Cholera Epidemic, 1854

This article focused on the Cholera outbreak experienced in Golden Square, an area in Central London, in the late summer of 1854. This incident has become significant in that it is now a milestone in Public Health and Epidemiology, or the study of incidence, distribution, and possible control of diseases and other factors relating to health, as represented by the removal of the handle on the Broad Street Pump. This was the result of John Snow’s conclusions that the water consumption from that pump was the source of the outbreak. He came to these conclusions using maps and scientific observations.

Snow originally encountered Cholera in 1831 during his apprenticeship as a surgeon-apothecary and in dong so created an initial theory that Cholera was a disease that was strictly in the gut and that it was the direct result of fluid loss. Snow eventually was presented with a golden opportunity to test his theory when the outbreak happened in 1853-1854. He did so by conducting research by investigating each home that experienced a mortality from Cholera, ultimately noticing that the centralized location of the deaths was near the Broad Street Pump using a spot map, using bars to decipher each mortality at that home (Figure 1). Later after Snow’s investigation, the Board of Health created a similar graph after learning of other deaths with improved location accuracy (Figure 2). Snow also eventually re-framed his dot map to represent the improved location accuracy and accurate mortality documentations.

The article, in conclusion, notes that Snow didn’t necessarily use a map to discover the source of the outbreak, but rather thought geographically. The text notes in the ending paragraphs that “the mere act of seeing data arranged graphically in space yields no new understanding without the support of a pathological theory.” (Brody et all, 68) Snow’s map demonstrating data arranged spatially of what he had investigated - because he had a pathological theory - does yield a new understanding as he stated that Cholera was a disease of the gastrointestinal tract. As time moved forward and as it continues to do so, a recurring theme appears of Snow being one who was a “clear-eyed modern thinker who saw the facts” and in turn caused the removal of the Broad Street Pump which halted the outbreak altogether.


  1. While Snows findings were of great importance, I find it interesting that though he did not actually use a map to come to his conclusions, the story remains, that he did.

  2. I find it interesting that he was smart enough to go around to each home and keep track of how many people had died. This was one step closer towards GIS, in that we are now able to have population maps, income maps, and so on and so forth. He was doing by hand what a computer is able to do now.

  3. Snow's imaging is incredible, and it is wonderful that we get to see what he visualized so long ago. I find it interesting that he could come to a conclusion of the source without having technology to track it for him.