Expansion of Coccidioidomycosis Endemic Regions in the United States in Response to Climate Change

Abstract

Coccidioidomycosis (Valley fever) is a fungal disease endemic to the southwestern United States. Across this region, temperature and precipitation influence the extent of the endemic region and number of Valley fever cases. Climate projections for the western United States indicate that temperatures will increase and precipitation patterns will shift, which may alter disease dynamics. We estimated the area potentially endemic to Valley fever using a climate niche model derived from contemporary climate and disease incidence data. We then used our model with projections of climate from Earth system models to assess how endemic areas will change during the 21st century. By 2100 in a high warming scenario, our model predicts that the area of climate‐limited 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 50%. The Valley fever endemic region will expand north into dry western states, including Idaho, Wyoming, Montana, Nebraska, South Dakota, and North Dakota. Precipitation will limit the disease from spreading into states farther east and along the central and northern Pacific coast. This is the first quantitative estimate of how climate change may influence Valley fever in the United States. Our predictive model of Valley fever endemicity may provide guidance to public health officials to establish disease surveillance programs and design mitigation efforts to limit the impacts of this disease.

Valley Fever: Environmental Risk Factors and Exposure Pathways Deduced from Field Measurements in California

“…There is widespread perception and modeling evidence that the southwestern U.S. is becoming not only drier, but also dustier [58,59]. The areas where a significant decrease in precipitation is predicted are also highly endemic for Coccidioides and the expansion of Coccidioides habitat due to climate warming has been predicted [60,61]. Furthermore, the diminishing groundwater in the San Joaquin Valley and the Mojave Desert is putting additional strain on air quality and coccidioidomycosis incidence because the ongoing drought in recent years has led to an increase in fallow agricultural fields, allowing the pathogen to become re-established, generating additional dust exposure pathways in Coccidioides-endemic areas [48][49][50][51][52].…”

“…There is widespread perception and modeling evidence that the southwestern U.S. is becoming not only drier, but also dustier [58,59]. The areas where a significant decrease in precipitation is predicted are also highly endemic for Coccidioides and the expansion of Coccidioides habitat due to climate warming has been predicted [60,61].…”

Suspected Locally Acquired Coccidioidomycosis in Human, Spokane, Washington, USA

“…The environmental range of Coccidioides spp. is not fully understood, and is possibly expanding in arid climates (11). This possible expansion creates a diagnosis and surveillance challenge because raising and maintaining clinical awareness in low-incidence or emerging settings is difficult.…”

Climate Change and Inpatient Dermatology

“…Additionally, states in which the fungus is usually endemic have also seen increases in the number of cases of coccidioidomycosis, with some studies estimating that climatic factors account for 75% of this increase [ 55 , 56 ]. Recently, Gorris et al modeled the geographic spread of coccidioidomycosis based on climate change patterns, ultimately projecting that the fungus’s endemic regions will more than double over the course of this century by expanding north into drier states in the western USA, such as Idaho, Wyoming, Montana, Nebraska, South Dakota, and North Dakota [ 57 ]. Altogether, these patterns and predictions suggest that dermatologists in these states may soon be including dimorphic fungi on their differentials in an unprecedented way.…”