infection with a fungus of the genus coccidioides, endemic to the southwestern united states. It is sometimes called valley fever but should not be confused with rift valley fever. infection is caused by inhalation of airborne, fungal particles known as arthroconidia, a form of FUNGAL spores. A primary form is an acute, benign, self-limited respiratory infection. A secondary form is a virulent, severe, chronic, progressive granulomatous disease with systemic involvement. It can be detected by use of coccidioidin.