John Snow Cholera Map as Rectified Raster Data, Water Pump Location Data, Deaths by Building Data

Abstract

John Snow’s investigation of cholera in 1850s London used analysis techniques that would now likely entail use of geographic information systems (GIS), as well as laying the foundation for modern epidemiology. Snow’s analysis demonstrates the power of maps and the underlying information, to visualize and solve complicated problems.

Cholera spread to the British Isles in the early 1830s and was a scourge to humans for fifty years more. The disease is horrific, causing the body to lose fluids quickly, the blood to thicken, and killing half of those afflicted in several days. Cholera spread quickly due to poor sanitation practices and misconceptions about its causes. Today we know that the disease is caused by a bacteria and it is usually spread through contaminated drinking water.

In 1854, a London physician named John Snow was living in the Soho District. London was experiencing its second cholera epidemic and Snow had been exposed to many infected patients. He showed no signs of cholera and for this and other reasons, did not uphold the common belief that the disease was passed by air. In early September, deaths from cholera increased drastically in Soho and Snow commenced his investigation into the quandary of cholera in the streets of his neighborhood.

Data can be read in GIS software such as ArcGIS or Quantum GIS, or online mapping tool such as ArcExplorer, GeoCommons, etc.