West Nile virus. Since its introduction in 1999, West Nile virus (WNV) has emerged as a major pathogen in the U.S., impacting wildlife, domestic animals, and humans. Mosquitoes belonging to the genus Culex have been implicated as the primary vectors of the virus. The distribution of WNV is clustered in space and time, with the highest concentrations of human cases occurring in urban areas in late summer. In 2002, the most intense activity of the virus took place in the North-Central U.S., especially in the Great Lakes regions. Illinois and Michigan reported the highest numbers of human cases and deaths: 884 cases (64 deaths) and 614 cases (51 deaths), respectively. The highest concentration of cases in these states was reported in the greater Chicago, Detroit and Grand Rapids region. While the future activity of WNV is still to unfold, based on its history in New York and in the Old World (esp. Israel), and on temporal activity patterns of related arboviruses, it appears likely that enzootic activity will continue in the North-Central U.S. with occasional epizootics/epidemics.

Environmental and social determinants of human risk during a West Nile virus outbreak in the greater Chicago area, 2002
Marilyn O Ruiz , Carmen Tedesco , Thomas J McTighe , Connie Austin and Uriel Kitron
International Journal of Health Geographics 2004, 3:8

Financial support: This research is supported by grant (TW05836) from the National Science Foundation as part of the NSF/NIH program in Ecology of Infectious Diseases
http://www.nsf.gov/awardsearch/showAward.do?AwardNumber=0429124
http://www.nsf.gov/od/lpa/newsroom/pr.cfm?ni=15000000000122

We plan to elucidate the local-scale ecological processes that result in WNV emergence, spread and persistence in urban environments by studying the virus in the greater metropolitan Chicago, Detroit, and Grand Rapids areas. We hypothesize that the North American, urban landscape presents a receptive environment into which WNV can invade, establish, and stably cycle. To quantify the emergence process into this environment, we aim to develop models with descriptive and predictive ability, using a multidisciplinary, spatially realistic, comparative approach that will consider case and infection distribution patterns in association with various risk factors. We also will gather data from avian and mosquito field studies and incorporate molecular evolution studies of the virus into the models. By integrating entomological, avian, viral, demographic and environmental data we will (1) generate a spatially realistic simulation model of WNV transmission that will allow us to explain virus transmission and predict enzootic and epizootic/epidemic patterns; and (2) develop up-to-date risk maps that will be used to determine surveillance and control measures.

Figure1. Age-adjusted West Nile virus human cases in 2002 in the greater Chicago region. Locations of dead birds are also displayed to demonstrate the congruency between locations of dead birds and human cases. Insert map shows the areas of significant clustering of human cases based on local Moran’s I statistic.

Participants:
The West Nile Virus project is a collaboration of UIUC, Michigan State University, Audubon - Chicago region, Illinois Department of Public Health and Michigan Department of Health.

UIUC:
Marilyn Ruiz
Uriel Kitron
Jeff Brawn
Tony Goldberg
Anna Schotthoefer
Robert Smith
Ken Kunkel
Tom Mctighe
Carmen Tedesco
John Andrews

Michigan State Univ:
Dr. Ned Walker
Dr. Steve Bolin
Dr. Bryan Epperson

Audubon-Chicago Region:
Judy Pollock
Karen Glennemeier

Illinois Dept. of Public Health:
Dr. Connie Austin
Dr. Linn Haramis

Other:
Dr. Robert McLean, APHIS, USDA, Nat'l Wildlife Research Ctr., Ft. Collins, CO
Dr. Gideon Wasserberg, USGS, National Wildlife Health Center, Madison, WI