Various approaches are used to identify West Nile virus (WNV) exposure areas, including unusual sightings of infected dead birds, mosquito pools or human cases both prospectively and retrospectively. A significant and largely unmet need in WNV research is to incorporate the temporal characterization of virus spread and locational information of the three components of transmission cycle-i.e., birds (reservoir), mosquitoes (vector), and humans (host)-on a localized scale. Exposure areas containing all three components of the WNV cycle in close proximity have higher potential to amplify an outbreak as compared to exposure areas delineated by a single component. In this paper, we introduce a novel approach, termed 'Nearest Neighbor Distance Time' or NNDT, to identify and retrospectively monitor WNV transmission cycles on various scales in the Twin Cities Metropolitan area of Minnesota. The NNDT model was implemented in a geographic information system using data from the period 2002 to 2006. The results indicated that 2002 and 2003 had three such WNV cycles, followed by one, two, and four respectively in 2004, 2005, and 2006. The NNDT method can be useful in locating chronically exposed areas and generating hypotheses about the transmission of WNV.
Bibliographical noteFunding Information:
This work is supported by the Doctoral Dissertation Fellowship and Thesis Research Grant of the University of Minnesota, the Dissertation Research Award of the Association of American Geographers, and the Graduate Research Award of the International Geographic Information Fund. The authors gratefully acknowledge the assistance of the editor and anonymous reviewers. Responsibility for the opinions expressed herein is solely that of the authors.
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- Exposure areas
- Space-time model
- Spider diagram
- West Nile virus