|XUE, LING - Kansas State University|
|SCOGLIO, CATERINA - Kansas State University|
Submitted to: Journal of the American Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2015
Publication Date: 9/17/2015
Citation: Xue, L., Scoglio, C., McVey, D.S., Cohnstaedt, L.W. 2015. Two introductions of Lyme disease into Connecticut: A geo-spatial analysis of human cases from 1984 to 2012. Journal of the American Medical Association. http://doi.org/10.1089/vbz.2015.1791.
Interpretive Summary: Lyme disease has become the most prevalent vector-borne disease in the United States and causes morbidity in humans, especially children. Using human cases to track the spread of Lyme disease is essential for long-term mitigation and containment of Lyme disease. The objective of this study was to analyze the introduction and spread of Lyme disease cases throughout Connecticut. This analysis of Lyme disease case data in Connecticut revealed strong spatial structuring of two disease clusters, indicating two spatially and temporally independent foci of origin and a recent shift from rapid epidemic Lyme disease spread throughout the state to lower and more stable endemic transmission. Lyme disease has spread uncontrolled throughout the state and understanding the spatial and temporal spread may aid in predicting current and future risks to guide interventions and mitigation strategies.
Technical Abstract: Lyme disease has become the most prevalent vector-borne disease in the United States and causes morbidity in humans, especially children. Using human cases to track the spread of Lyme disease is essential for long-term mitigation and containment of Lyme disease. The objective of this study was to analyze the introduction and spread of Lyme disease cases throughout Connecticut. The study included geographic information system analysis of publically available Connecticut Department of Public Health yearly Lyme disease cases in 169 towns from 1984, 1985, and 1991 to 2012. The spatial and temporal origins of Lyme disease in Connecticut and analysis of the subsequent spread were analyzed to identify at risk areas and estimate future incidence. The analysis identified two distinct spatial and temporal clusters of Lyme disease cases, one in Western and Eastern Connecticut. Both epidemic clusters of cases were defined by long-term significant spatial autocorrelation. Large total numbers of Lyme cases are distributed in proximity of Eastern and Western clusters, whereas fewer total numbers of cases are distributed outside the two clusters. The incidence-weighted geographic mean analysis indicated a northern trend of geographic expansion for both epidemic clusters. In the Eastern Connecticut region, as the epidemic progressed, the yearly shift in the geographic mean (rate of epidemic expansion) decreased each year until spatial equilibrium is reached in 2007. The equilibrium indicates a transition from epidemic Lyme disease spread to stable endemic transmission and is associated with a reduction in incidence. In Western Connecticut, the parabolic distribution of the yearly geographic mean indicates after establishment (1988), the epidemic quickly expanded northward and established equilibrium in 2009. Historical case distributions are useful tools to explain vector borne disease introductions and subsequent geographic expansion in the absence of disease vector data. Risk, geographic expansion rate, and future incidence can be predicted to guide efficient prevention and control strategies in high risk areas.