Climate controls on valley fever incidence in Kern County, California

Abstract

Coccidiodomycosis (valley fever) is a systemic infection caused by inhalation of airborne spores from

Intensified dust storm activity and Valley fever infection in the southwestern United States

“…The incidence of Valley fever has increased eightfold from 1998 to 2011 in the endemic areas (Arizona, California, Nevada, New Mexico, and Utah) [ CDC , 2013]. Although little is known of the underlying forces, previous studies have concluded that the overall increasing trend in Valley fever incidence is not explainable through changes in medical practice, disease surveillance, land use, climate, or weather variability alone [ Zender and Talamantes , 2006; Comrie , 2005; Park et al ., 2005; Sprigg et al ., 2014]. …”

“…Both counties have reported the largest numbers of cases during the study period. Valley fever has been found to be associated with several controlling factors, including precipitation, temperature, and dust [ Zender and Talamantes , 2006; Comrie , 2005; Park et al ., 2005]. In Arizona, precipitation and dust are found to be the most useful predicting factors to Valley fever incidences [ Comrie , 2005; Park et al ., 2005; Tamerius and Comrie , 2011].…”

Recent Advances in Our Understanding of the Environmental, Epidemiological, Immunological, and Clinical Dimensions of Coccidioidomycosis

“…A recently developed mathematical model has shown a strong correlation between seasonal precipitation variation and the annual number of cases of coccidioidomycosis reported to Arizona Public Health for Pima and Maricopa County residents (65,66). Data from Kern County in California show a single peak of infection associated with dry periods after the winter rainy season, with relatively equal rates during the rest of the year (67,68). There is a general lack of information about climatic factors affecting rates of disease in the remainder of the area of endemicity, specifically in Mexico and South America (45,69).…”

Evaluation of Coccidioides exposures and coccidioidomycosis infections among prison employees.

“…Saltation contributes to an effect called sandblasting, where airborne dirt and dust particles repeatedly impact the soil surface downwind, dislodging even more particles in the process. Researchers have speculated that saltation may rupture the fungal structure of Coccidioides, and sandblasting can disperse the airborne Coccidioides spores at wind speeds lower than those required to directly entrain either the fungus or its spores [Zender and Talamantes 2005]. However, naturally occurring dust storms, combined with ongoing soil disturbing activities such as farming and construction that occur on land adjacent to each prison, can recoat stabilized soil and may reduce or shorten the possible benefit of soil treatment.…”

“…Previous studies have hypothesized that Coccidioides spores (vegetative fungal cells in a resting state) are most abundant in the soil after heavy rains and may be most effectively dispersed during dry, hot periods, such as prolonged droughts [Smith et al 1946;Schneider et al 1997;Kolivras and Comrie 2003;Comrie 2005]. Thus, increased incidence of infection often occurs after a heavy wet season followed by a prolonged dry spell [Zender and Talamantes 2005]. Incidence in California is thought to be seasonal, with peak incidence occurring during the winter months [Kirkland and Fierer 1996].…”