Thematic Maps

Mapping Disease (1 & 2)

Mapping Disease (Part 1)
click for part 2

One of the more innovative and practical uses of thematic maps was the disease map. For more than 200 years investigators have used maps to visually represent data on disease incidence and mortality in order to discover clues and identify sources of risk. And while modern maps often focus on cancer or other endemic diseases, early maps dealt with terrifying epidemic diseases such as cholera and yellow fever. The medical historian Saul Jarcho writes, for example, “the cartography of disease owes its genesis to the abrupt, terrifying challenge which epidemic outbreaks presented, whereas endemic disease, more or less constantly active, offered no comparable stimulus to cartographic creativity. Plague, yellow fever, and cholera – all exotic – accomplished what tuberculosis could not” (Jarcho 1969).

It was yellow fever’s grasp on New York City in the late 18th century, for example, that prompted what is considered the world’s first disease spot map. Dr. Valentine Seaman, a surgeon at the New York Hospital, assembled a map of yellow fever deaths in what is now the Lower East Side of Manhattan. At the time he created his map, physicians were embroiled in a heated debate about the source of yellow fever contagion. Unlike the majority of the medical establishment who believed the disease was being spread from person to person, Seaman argued that it was filthy conditions and direct contact with contaminated people or objects that led to transmission (Stevenson 1965).

He, therefore, used his map to graphically portray the relationship between yellow fever deaths and what he called “putrid eflluvia.” In particular, he mapped yellow fever deaths in relation to the Roosevelt Street drain, which, he felt, was a likely source of contagion owing to the fact that it was “covered with numerous perishable materials…in addition to other putrid matters” (Seaman 1796; Seaman 1798).

It turned out, however, that Seaman was incorrect. Instead of “putrid effluvia,” mosquitoes were responsible for the spread of yellow fever. More than 100 years after the 1798 publication of Seaman’s map in The Medical Repository, Walter Reed and the Reed Commission, working in Cuba during the Spanish American War, proved that the mosquito Aedes aegypti was responsible for spreading the disease [2].

Nevertheless, despite Seaman’s incorrect theory on the transmission of yellow fever, his contribution to cartography remains important (Stevenson 1965). click for part 2

[2] During the Spanish American War Americans lost more soldiers to disease, particularly yellow fever, than to the fighting itself. In response, the American government set up the Reed Commission to investigate the source of yellow fever. As part of their research, the Commission deliberately infected mosquitoes and allowed them to feed on volunteers, including members of the Commission (Topper 1997). Many of the volunteers (including Commission members) contracted the disease and most of these recovered. One Commission member, Jesse Lazear, died from the disease.

© 2006 ZevRoss Spatial Analysis