We find weak but statistically significant links between disease incidence and antecedent climate conditions. Precipitation anomalies eight and twenty months antecedent explain only up to 4% of monthly variability in subsequent valley fever incidence during the 23 year period tested. This is consistent with previous studies suggesting that C. immitis tolerates hot, dry periods better than competing soil organisms, and, as a result, thrives during wet periods following droughts. Furthermore, the relatively small correlation with climate suggests that the causes of valley fever could be largely anthropogenic in Kern County.
Seasonal climate predictors of valley fever in Kern County are similar to, but much weaker than those in Arizona, where previous studies find precipitation explains up to 75% of incidence. Hypotheses for the discrepancy between climate associations with valley fever in California and Arizona will be discussed. Finally, Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) climate simulations will be used to diagnose potential future changes in regions endemic for valley fever through the end of the 21st century.
Supplementary URL: http://www.ess.uci.edu/~zender