Tuesday, May 17, 2016

Map-making of the London Cholera Epidemic

Cholera is an acute epidemic infectious disease caused by the bacterium Vibrio cholerae. A soluble toxin elaborated in the intestinal tract by the bacterium activates the adenylate cylase of the mucosa, causing active secretion of an isotonic fluid resulting in profuse watery diarrhea, extreme loss of fluid and electrolytes, and dehydration and collapse, but no gross morphologic change in the intestinal mucosa (Sy Kraft B.A, 2015).
The first outbreak of cholera in London was around 1830, the next outbreak was in 1853, which in the vicinity of Golden Square, the center of London. Dr John Snow was a British physician who is considered one of the founders of epidemiology for his work identifying the source of a cholera outbreak in 1854 (BBC, 2014). He argued that cholera was a localized disease of the gut, and that its symptoms were entirely the result of fluid loss (1854). The causal agent, he reasoned, must enter by mouth, multiply within the gut, and then spread to others by the faecal-oral route ( Brody, Rip, Johansen, Paneth and Rachman, 2000). Snow first hypothesized cholera might be transmitted by drinking water. He went to every house where people died because of cholera, and made dot map of which related house’s location on a map (Figure 1).
Before Snow drew his dot map, Edmund Cooper in the Metropolitan of Sewers investigated from the public complains that the linking to the  sewers to the cholera outbreak. From his study of this map (Figure 2), and of the sewers themselves, Cooper concluded that the houses nearest the gully-holes had no greater number of deaths than houses not so situated. The sewers of the area where most of the deaths were clustered were in reasonable condition.  (Brody, Rip, Johansen, Paneth and Rachman, 2000). In his report, Cooper added: “Since the outbreak, six men have been employed in these lines of sewers getting up information on this subject, all of whom, I am glad to state, are quite healthy, and entirely free from disease.” (1854) . Therefore, he rejected his previous hypothesis that sewer gas could not cause the spread of cholera.
Later, the government made a map which contained more details (Figure 3).
In this case, Geographic Information System (GIS) played an important role, both Snow and Cooper used map to analyse data of the deaths of cholera, it was able to easily illustrate the possibility cause of the spreading of cholera.

Figure 1.John Snow’s of cholera deaths.
Figure 2. Edmund Cooper’s map.
Figure 3. Government map.
Retrieved May 16, 2016, from http://www.bbc.co.uk/history/historic_figures/snow_john.shtml
Brody, H., Rip, M. R., Vinten-Johansen, P., Paneth, N., & Rachman, S. (2000). Map-making and myth-making in Broad Street: the London cholera epidemic, 1854. The Lancet, 356(9223), 64-68.
Epidemiological Society. Lancet 1854; ii: 531.
Snow J. On the mode of communication of cholera. London: John Churchill, 1849 (1st edn).
Retrieved May 16, 2016, from http://www.medicalnewstoday.com/articles/189269.php
Cooper E. Metropolitan Commission of Sewers, eastern division of Westminster: report Sept 22, 1854). Manuscript MCS 478/1-28, London Metropolitan Archives.

1 comment:

  1. I wonder if it is possible to use similar systems to plot all diseases, and find the epicenter of things like Ebola, to track them back to their original source.