Disease, Geography of

Historical Foundations

Although the acknowledgment of the relationship between environment and health can be traced back to 400 BC, when Hippocrates wrote On Airs, Waters, and Places, the first high-profile, and best-known, study of disease geography is likely that undertaken by John Snow. There was an epidemic of cholera in London during the year 1854. Snow, who hypothesized that cholera was a water-borne disease, plotted cases of cholera in the London neighborhood of Soho on a dot map and identified a water pump on Broad Street as the likely source of the epidemic. The handle was removed from the pump, disabling it, and the epidemic abated. Snow's use of dot maps in identifying the source of the epidemic was novel and is the earliest case of the use of disease mapping in addressing a health problem.

Causes of Spatial patterning

There are many reasons for the patterns of disease that we observe. In Snow's case, the reason for the spatial patterning of cholera cases in Soho was the location of a pump making contaminated water available to the local population. It is clear that the quality of the physical environment in which people live is of great importance in affecting rates of disease. The physical environment includes both the natural environment and the built environment. Commonly explored features of the physical environment, which can affect spatial patterns of disease, include air and water quality and sources of pollution that may be point sources (such as facilities releasing toxics into the air), nonpoint sources (such as agricultural runoff), and mobile sources (such as automobile exhaust). Climate is a factor of growing importance due to global climate change, which has the potential to affect the locations where disease vectors, such as mosquitoes that carry malaria, can survive. Built environment considerations range from the quality of indoor air affecting asthma rates to the walkability and safety of neighborhoods affecting rates of obesity.

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