Coccidioidomycosis
Coccidioides immitis and C. posadasii are the etiologic agents of coccidioidomycosis. These dimorphic fungi are residents in selected desert soils of the lower Sonoran life zone. The areas of highest endemicity in the United States include the southwestern Arizona, the San Joaquin Valley of California and west Texas and (Supporting Figure S4). C. immitis is the predominant species in California, whereas C. posadasii is found in the other endemic areas. An estimated 150 000 infections occur annually in the United States, primarily in residents or in individuals with travel to endemic areas. Outside of the United States, this fungus is found in northern Mexico with limited endemicity in Central and South America. Coccidioidomycosis is acquired by inhalation of arthroconidia that undergo transformation into spherules resulting in a primary pulmonary infection. Endospores from mature spherules can spread hematogenously to extrapulmonary sites. Once the host has developed cellular immunity, protection is complete and long-lasting despite ongoing exposure unless a profound change in host immunity occurs. Coccidioidomycosis occurs in 1.5–8.7% of the transplant recipients in endemic areas, typically in the first posttransplant year. Several cases of donor-derived coccidioidomycosis in transplant recipients have been reported.