Retrospective analysis of geospatial and demographic risk factors for human West Nile virus (WNV) infection in the Texas Panhandle, 2003

Background: In Texas in 2003, human West Nile virus (WNV) infections occurred more commonly in the Panhandle. Playa lakes in the Texas Panhandle are common mosquito breeding grounds and gathering sites for birds. We investigated the relationship between human WNV infections and geographic, demographic and socioeconomic factors for 65 counties of the Texas Panhandle.

Methods: 29 of 65 counties had at least one reported human WNV case. Counties with no cases of human WNV were compared to counties with one or more human WNV cases. After testing for collinearity, independent variables were tested individually against the WNV binary dependent variable. Independent variables tested were percent population age 50 and older, percent population living below federal poverty level, percent population engaged in agriculture, age of housing, percent population non-Hispanic White, proportion playa lake area and non-playa surface water area. Using a Chi-square test, variables with p < 0.1 were retained in a logistical regression model.

Results: Of the variables tested, only the proportion of county area covered with playa lakes was found to be positively correlated with the presence of human WNV infections in a county. A negative correlation was observed with percent non-Hispanic White.

Conclusions: On a county level analysis, human WNV infections in 2003 were associated with proportion of county covered by playa lakes. Mosquito abatement activities to include playa lakes may be an important strategy for preventing transmission of WNV in the Texas Panhandle.