Coccidioidomycosis Climate Niche Model for Predicting Current and Future Endemic Regions in the United States through the 21st Century and Applications to Environmental Soil Sampling

Coccidioidomycosis, otherwise known as Valley fever, is an infectious fungal disease endemic to parts of North, Central, and South America. Humans contract Valley fever by inhaling fungal spores of the genus Coccidioides that grow in desert-like soils. However, detecting Coccidioides in the soil is difficult due to its sporadic growth, which is possibly driven by fine-scale soil properties that promote the presence of the fungi. At the larger scale, the spatial distribution and number of Valley fever cases is in part shaped by climate factors. As such, climate change may cause the area endemic to Valley fever to change, exposing new populations. We developed a county-level climate niche model to estimate the current area potentially endemic to Valley fever using observed relationships between contemporary climate and disease incidence. Then, we used this model to predict changes in the endemic area during the 21^st century using climate projections from 35 CMIP5 models. We calculated the spread in our outcome variables from the Earth system models, estimating the effects of anomalous climate conditions. Our analysis indicates by 2095 under RCP8.5 the area of endemicity will more than double, the number of affected states will increase from 12 to 17, and the number of Valley fever cases will increase by over 50%. Now, we are building upon our climate niche model by adding chemical and physical soil properties to develop a tool for informed environmental sampling of Coccidioides. We are using characteristics of positive soil samples from Washington state as model verification. Increased environmental detection of Coccidioides would help us understand the fine-scale soil properties driving the presence of these fungi and in turn, further finesse our Coccidioides niche model.