Spatial and temporal structure of typhoid fever in Washington, D.C., 1895--1909: A geographic information systems exploration of urban health concerns.

摘要

The period between 1880 and 1920 was one of the most dynamic in the history of medicine. Morbidity and mortality rates for infectious diseases dropped quickly. Concurrently, miasmatic theory gave way to germ theory. Many of these dynamic changes occurred in the urban centers of North America, which were also entering into a period of dramatic growth and change. Following the 1905 completion of infrastructure improvements intended to improve public health in Washington, D.C., typhoid fever rates unexpectedly increased. Previously, for mitigation purposes, Dr. George Kober investigated a typhoid epidemic in 1895, and as a result of the 1906 increase in typhoid morbidity the United States Public Health and Marine-Hospital Service conducted investigations between 1906 and 1909 to better understand the origins of typhoid in the city. These studies include dot maps of typhoid case locations for the entire 1895 epidemic, at two-week intervals for 1906, 1907, and 1908, and monthly intervals for 1909. These point locations are used to construct a geographic information system (GIS) displaying the spatial distribution of individual typhoid cases. The creation of this GIS allows for the investigation of urban typhoid at a localized geographic scale. The temporal resolution of the data and supplementary data included in the reports provides an opportunity to explore urban typhoid within years, between years, to compare morbidity to mortality, and to compare the spatial pattern of multiple diseases. This dissertation describes the creation of this GIS and the results of the spatial analyses using Ripley's K-function and the Gi* statistic to evaluate spatial clustering patterns. The Gi* statistic identified localized hotspots that refute the conclusions of the original reports. Typhoid clusters varied in size and location, and lacked temporal stability. The findings xii of this dissertation indicate that typhoid in early twentieth century Washington, D.C. originated from multiple sources whose impact decreased over time. Studies of this type make use of geospatial approaches unavailable when the original data were collected, in order to investigate potential patterns of typhoid fever invisible a century ago. This research helps to provide a better understanding of the historical geography of urban health in general.