Regional Increases in Incidence of Coccidioidomycosis (Valley Fever) - Arizona, 2005-2022.

Incidence of coccidioidomycosis (Valley fever), a fungal infection caused by inhalation of Coccidioides species spores, has increased substantially across the southwestern United States in association with increasing aridity, warming temperatures, and precipitation volatility. Arizona and California report >95% of U.S. coccidioidomycosis cases, and incidence in Arizona has increased statewide. Patterns within Arizona's distinct climatological regions have not been characterized, especially in regions outside the known zone of persistently high levels of disease occurrence (hyperendemicity) in the southwest Sonoran Desert region. In this study, surveillance data reported to the Arizona Department of Health Services since 2005 were used to calculate coccidioidomycosis incidence within six ecological regions. During 2005-2022, annual incidence approximately doubled in Arizona, with >95% of cases reported from the Sonoran Desert region. Although the Plateaus and Mojave Desert regions (in the northern parts of the state) reported <1.5% of Arizona cases during this period, these regions experienced the highest relative increases in incidence from the 2005-2007 period to the 2020-2022 period. During 2020-2022, coccidioidomycosis incidence in the Plateaus region was 6.61 times the incidence during 2005-2007 (95% CI = 4.22-10.30), and in the Mojave Desert region, incidence was 4.50 times that during 2005-2007 (95% CI = 3.45-5.89). The Plateau and Mojave regions also reported the highest relative increases in incidence from the 2014-2016 period to the 2020-2022 period. Large relative incidence increases in northern regions, including cooler and wetter regions generally considered less suitable for Coccidioides species establishment and transmission, necessitate targeted public health messaging in these areas and support ongoing investigation into the causes of these increases.