Fluctuations in Climate and Incidence of Coccidioidomycosis in Kern County, California

Jorge Talamantes,Charles S Zender,Sam Behseta

doi:10.1196/annals.1406.028

Abstract

Coccidioidomycosis (Valley Fever) is a fungal infection found in the southwestern United States, northern Mexico, and some places in Central and South America. The fungi that cause it (Coccidioides immitis and Coccidioides posadasii) are normally soil dwelling, but, if disturbed, become airborne and infect the host when their spores are inhaled. It is thus natural to surmise that weather conditions, which foster the growth and dispersal of Coccidioides, must have an effect on the number of cases in the endemic areas. This article reviews our attempts to date at quantifying this relationship in Kern County, California (where C. immitis is endemic). We have examined the effect on incidence resulting from precipitation, surface temperature, and wind speed. We have performed our studies by means of a simple linear correlation analysis, and by a generalized autoregressive moving average model. Our first analysis suggests that linear correlations between climatic parameters and incidence are weak; our second analysis indicates that incidence can be predicted largely by considering only the previous history of incidence in the county-the inclusion of climate- or weather-related time sequences improves the model only to a relatively minor extent. Our work therefore suggests that incidence fluctuations (about a seasonally varying background value) are related to biological and/or anthropogenic reasons, and not so much to weather or climate anomalies.

Highlights

Much is known about the biological, medical, and the epidemiologic aspects of Coccidiodes immitis (C. immitis) and Coccidiodes posadasii (C. posadasii), the fungi that cause Valley Fever
Our work suggests that fluctuations in incidence are probably due more to human activities or biological processes taking place in the field, rather than to climatic fluctuations
Studies to date have demonstrated a strong incidence–climate connection in Arizona,[15] but not in California.[17]. Perhaps this is because the latter studies use wind and not PM10 as a proxy for spore abundance in the atmosphere

Summary

A Review

JORGE TALAMANTES,a SAM BEHSETA,b AND CHARLES S. ZENDERc aDepartment of Physics and Geology, California State University, Bakersfield, California, USA bDepartment of Mathematics, California State University, Bakersfield, California, USA cDepartment of Earth System Science, University of California, Irvine, Irvine, California, USA

INTRODUCTION

Findings

DISCUSSION