Case Assignment: Epidemiological Event

Case Assignment: Epidemiological Event

Case Assignment: Epidemiological Event

Week 1 discussion Discussion Part One Discuss one historical epidemiological event or accomplishment that has left an impact on healthcare as we know it. Clearly identify, describe, and define key points or people in the event or accomplishment.

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Although epidemiology as a discipline has blossomed since World War II, epidemiologic thinking has been traced from Hippocrates through John Graunt, William Farr, John Snow, and others. The contributions of some of these early and more recent thinkers are described below.(5)

Circa 400 B.C.
Epidemiology’s roots are nearly 2,500 years old.
Hippocrates attempted to explain disease occurrence from a rational rather than a supernatural viewpoint. In his essay entitled “On Airs, Waters, and Places,” Hippocrates suggested that environmental and host factors such as behaviors might influence the development of disease.

1662
Another early contributor to epidemiology was John Graunt, a London haberdasher and councilman who published a landmark analysis of mortality data in 1662. This publication was the first to quantify patterns of birth, death, and disease occurrence, noting disparities between males and females, high infant mortality, urban/rural differences, and seasonal variations.(5)

1800
William Farr built upon Graunt’s work by systematically collecting and analyzing Britain’s mortality statistics. Farr, considered the father of modern vital statistics and surveillance, developed many of the basic practices used today in vital statistics and disease classification. He concentrated his efforts on collecting vital statistics, assembling and evaluating those data, and reporting to responsible health authorities and the general public.(4)

1854
In the mid-1800s, an anesthesiologist named John Snow was conducting a series of investigations in London that warrant his being considered the “father of field epidemiology.” Twenty years before the development of the microscope, Snow conducted studies of cholera outbreaks both to discover the cause of disease and to prevent its recurrence. Because his work illustrates the classic sequence from descriptive epidemiology to hypothesis generation to hypothesis testing (analytic epidemiology) to application, two of his investigations will be described in detail.

Snow conducted one of his now famous studies in 1854 when an epidemic of cholera erupted in the Golden Square of London.(5) He began his investigation by determining where in this area persons with cholera lived and worked. He marked each residence on a map of the area, as shown in Figure 1.1. Today, this type of map, showing the geographic distribution of cases, is called a spot map.

Figure 1.1 Spot map of deaths from cholera in Golden Square area, London, 1854 (redrawn from original)

Image Description

Source: Snow J. Snow on cholera. London: Humphrey Milford: Oxford University Press; 1936.
Because Snow believed that water was a source of infection for cholera, he marked the location of water pumps on his spot map, then looked for a relationship between the distribution of households with cases of cholera and the location of pumps. He noticed that more case households clustered around Pump A, the Broad Street pump, than around Pump B or C. When he questioned residents who lived in the Golden Square area, he was told that they avoided Pump B because it was grossly contaminated, and that Pump C was located too inconveniently for most of them. From this information, Snow concluded that the Broad Street pump (Pump A) was the primary source of water and the most likely source of infection for most persons with cholera in the Golden Square area. He noted with curiosity, however, that no cases of cholera had occurred in a two-block area just to the east of the Broad Street pump. Upon investigating, Snow found a brewery located there with a deep well on the premises. Brewery workers got their water from this well, and also received a daily portion of malt liquor. Access to these uncontaminated rations could explain why none of the brewery’s employees contracted cholera.

To confirm that the Broad Street pump was the source of the epidemic, Snow gathered information on where persons with cholera had obtained their water. Consumption of water from the Broad Street pump was the one common factor among the cholera patients. After Snow presented his findings to municipal officials, the handle of the pump was removed and the outbreak ended. The site of the pump is now marked by a plaque mounted on the wall outside of the appropriately named John Snow Pub.