Environmental Variability and Disease Emergence: Spatial Patterns of Lyme Disease Emergence in Virginia

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Disease emergence is an inherently geographical phenomenon, and factors at multiple spatial scales, such as international trade and local land-use change, interact to contribute to a disease's appearance in the human population for the first time or its spread beyond the original range. In spite of great advancements in the control of infectious diseases over the last several decades, endemic zoonotic diseases like Lyme disease, the most common vector-borne disease in the United States, continue to expand in range, and the mechanisms underlying these emergence events are poorly understood. This research project will examine the diffusion of Lyme disease as it emerges southward along the East Coast, using Virginia as a case study because of the state's location on the front line of human Lyme disease expansion. A key objective for the investigators is to determine the role of variability in human and physical environments on the disease's continued spread at multiple spatial scales. Specific research goals are to quantify the spatial and temporal emergence pattern of human Lyme disease in Virginia between 1998 and 2010 to determine where human case clustering occurs; to characterize landscape-level factors in the human and physical environments that are associated with human cases; and to develop a predictive geographic model of human incidence to identify areas of Virginia that are at highest risk for future Lyme disease emergence. The interdisciplinary research team, combining expertise in geography, forestry, statistics, and entomology, will use statistical analyses to examine the diffusion of Lyme disease in Virginia over the past decade, pinpointing case clusters. GIS analyses will link human and environmental conditions with human cases from 1998 to 2010 and allow for an improved understanding of environmental conditions associated with Lyme disease emergence. Finally, combined statistical and geospatial tools will assist in the development of a predictive map and model of human incidence that will allow public health officials to target their use of sometimes scarce human and financial resources in the prevention of future Lyme disease cases. This research will provide new insights into the ways in which variability in human and physical environments at multiple spatial scales contribute to disease emergence. The bulk of research examining the relationship between Lyme disease and environmental variability has focused on endemic areas, neglecting study of the environmental influences at the edges of the disease's range expansion. Understanding such relationships as the disease emerges in non-endemic areas is crucially important to disease prevention and control, and the results of this research will provide public health departments with critical information to be used in communications with health clinics and physicians' offices. Lyme disease has a significant public health burden in the U.S., and an improved understanding of the disease's emergence pattern will enhance diagnosis and reporting efforts, and ultimately decrease the number of human cases. The project will improve scientific understanding of disease emergence in general, and more specifically Lyme disease emergence, and the approach and methods used in the research can be applied to the study of other vector-borne diseases. The research will provide opportunities for graduate and undergraduate students to gain research experience in an interdisciplinary setting, and the Virginia Department of Health will disseminate the results to the general public and physicians to improve public health.