The cholera outbreak of 1954 provided John Snow
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The cholera outbreak of 1954 provided John Snow with an opportunity to totally disprove the Miasma theory, as it provided a concentrated outbreak of cholera. Most of the cases at the time primarily occurred within a small area: over 500 deaths within an area of 250 yards. This must have led Snow into reasoning that the source of contamination must have been a shared resource within the community, probably the much frequented street pump in Broad Street, as all the deaths had taken place only a short distance from the well. However, his hypothesis in 1854 was a culmination of work that had been done as a result of the previous outbreaks of 1831 and 1849, these outbreaks had enabled John Snow to narrow down on the gastrointestinal tract as the main area of attack for cholera based on the symptoms. The fact that cholera mainly attacked the gastrointestinal tract had led Jobhn Snow to believe that the mouth was most likely the point of entry for the causative agent. This coupled with the differences that had been highlighted between cases in Salford Manchester, and cases in London, had shifted focus to the water supply systems, hence leading to increased focus on contaminated water as the main causative agent. This hypothesis was proven by findings of a spot map on Broad Street, which based on its distribution, confirmed the Broad Street pump as the main cause of the outbreak; therefore, contaminated water as the main cause of cholera. This assertion was confirmed by interviewing members of the public who had been affected, confirming the pump as their main source of water (Snow, n.pag).
The main clue that Snow had that helped him determine the source of the outbreak was the distribution of the deaths, and their distance from the much frequented water pump. He was then able to confirm the source by establishing that those who had died had drank water from the Broad Street pump. Anomalies such as the three children, or the brewery and the prison, further served to confirm his suspicions, as they had for one reason or another, not taken water from the contaminated pump, with the exception of the three children. The fact that the cases of cholera declined so sharply after the removal of the water pump further cemented Snow’s belief that the Broad Street pump was the source of the outbreak (Johnson, 195).
Spot maps are simply drawings on a map of the affected geographical area, marking the distribution of fatalities or cases of a disease, in order to help in the establishment of the source of the outbreak. Essentially, the spot maps helped John Snow disprove the miasma theory, by displaying a distribution pattern that was inconsistent with air borne diseases. Some cases were of people who could not have breathed contaminated air, as they had never been to Broad Street.
John Snow diligently followed up data that did not fit his hypothesis, in order to be able to rule out other causes of the epidemic. First he followed up distant cases of cholera to find out whether they had in any way been in contact with water from the well in order to be certain that the well was the cause of the outbreak. For instance, he followed up cases of three school children who did not live near the well, and discovered that the well was located on their way to school. In another instance, he found that a restaurant whose 9 customers had died during the outbreak, usually served their food with glasses of water obtained from the well. Further, in order to prove his hypothesis, Snow also visited places that were located within Broad Street but did not report cases of cholera; these included a brewery and a prison (Johnson, 196). In the case of the brewery, the men drank only liquor they had made, or drank water from the brewery’s own well, while the prison had its own well and bought water. These cases only served to reaffirm Snow’s hypothesis, hence the need to follow them up.
Works Cited
Johnson, Steven. The Ghost Map: The Story of London’s Most Terrifying Epidemic – and How itChanged Science, Cities and the Modern World. Riverhead Books, 2006. Print
Snow, John. On The Mode of Communication of Cholera. London: John Churchill, 1855. Web.
