An Exploratory Analysis of Associations between Drought and Coccidioidomycosis Incidence in Arizona and California Open Access

Parker, Gwendolyn Honor (2015)

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Coccidioidomycosis is an infectious disease caused by inhalation of the fungal pathogens Coccidioides immitis and Coccidioides posadasii, endemic to the southwestern United States. The past two decades have seen a striking increase in disease incidence, particularly in Arizona and California. This increase is hypothesized to have been impacted by climate and environmental conditions. Previous studies have analyzed the impact of climate conditions on coccidioidomycosis incidence in multiple counties in California and Arizona, establishing a link between sequences of wet and dry/warm climate conditions and coccidioidomycosis incidence in Arizona, although not in California. This study analyses the associations between coccidioidomycosis case counts and temperature, precipitation, and two drought indices in 3 counties in Arizona and 20 counties in California through bivariate and multivariate regression analyses. Patterns of alternating wet and dry climate conditions were associated with coccidioidomycosis case counts in both Arizona and California, captured through both precipitation and drought index variables. Conclusions from this study reveal a previously unidentified pattern of climate conditions impacting coccidioidomycosis in California; inclusion of drought indices is shown to have utility in elucidating this pattern. These results will contribute to our understanding of how disease patterns may change in light of expanding and intensifying drought in the region.

Table of Contents

Introduction. 1


Geographic Range

Climate Pressures


Purpose of Study

Methods. 8

Data Collection

Exploratory Analysis

Bivariate Analysis

Multivariate Analysis

Results. 13

Exploratory Analysis Bivariate Analysis Multivariate Analysis Discussion. 18


Recommendations for Future Study

Conclusion. 23

Figures & Tables. 24

Appendices. 38

References. 39

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