The Role of Climatic and Environmental Variability on West Nile Virus in Harris County, Texas, 2006-2007

Abstract

Between the years 2006-2007, Harris County, located at the heart of the Houston metropolitan area, experienced a nearly 90% decline in the number of female mosquitoes which tested positive for the West Nile virus. Different theories exist as to why such a precipitous drop occurred and this study attempts to determine the extent to which climatic variability between the two years played a role. The Mosquito Control Division of Harris County Public Health and Environmental Services gathered the data on vectors and reservoirs. Then using GIS, spatial analysis, and geostatistical tools the vector and reservoir data was compared to climatic data to investigate any changes in viral distribution. Previous studies of the area until now have used a limited amount of climatic data; this study seeks to improve the resolution of climatic data analyzed. A higher resolution of data was achieved by including as-of-yet unused data from a network of over 150 gauges maintained by various state and local agencies in addition to previously used data from NOAA COOP stations. Using this dense network of station's values for precipitation, temperature and other climatic variables were interpolated for all of Harris County and used in the analysis. Based on results, water availability was the most likely out of all the climatic variables to the precipitous drop of West Nile virus positive female mosquitoes from 2006-2007. Correlations between all climatic variables and mosquito abundance and West Nile virus positives showed mixed results compared to a previous study in the same area.