Map-making and myth-making on Broad Street: the London cholera epidemic, 1854

Today, Geographic Information Systems (GIS) are used for many disciplines to inform researchers and answer questions.  Researchers can use computer programs like ArcGIS to analyze maps to determine where things happen.  Most people trace the root of utilizing maps to answer scientific questions to John Snow, who is said to have utilized a street map of Golden Square in central London to successfully locate the source of a cholera outbreak.  He plotted the locations of those who had died from Cholera on the map and found that most of the deaths were localized around the Broad Street water pump.  His report to the Board of Guardians led the city to shut off the pump, which stopped the outbreak of cholera.  Brody et al (2000) traced written records and maps from other medical researchers at the time to find that history has embellished and idealized the story of Dr. Snow’s epidemiological research.

Snow had extensive practice working in the medical field, studying the epidemiology of cholera, and had early on in his research hypothesized it was transmitted by water.  He originally set out to see if sewage had contaminated one of the two water supply lines in the city, and went door-to-door making note of where cholera-related deaths had taken place.  In the midst of this research, the cholera outbreak at Golden Square took place, and he quickly investigated the area.  However, Snow used his own deduction, unaided by a map, to determine that the Broad Street pump was the source of the contamination.  It was later that he returned to a map with a plot of the deaths to help demonstrate that the outbreak was localized around the single pump.  So while Snow did make use of maps, they were not his main tool in figuring out the Golden Square cholera outbreak.

Other researchers at the time, however, relied on maps as their main research tool.  Edmund Cooper used a disease map prior to Snow’s first use of a map in 1854 (shown in Figure 3).  Cooper’s map plotted cholera-related deaths as black bars drawn on the house where the death occurred.  The only original contribution made by Snow to what would later be called GIS is the use of a Voronoi diagram to show the area in the Square that was located closer to the Broad Street pump than any other pump (shown as the small dotted line in figure 1).  Although history credits John Snow as an early GIS researcher, it should credit him more with being a good critical thinker who used his background in cholera research to solve the Golden Square outbreak.

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.