What causes coccidioidomycosis?

Updated: Aug 27, 2019
  • Author: Duane R Hospenthal, MD, PhD, FACP, FIDSA, FASTMH; Chief Editor: Michael Stuart Bronze, MD  more...
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Coccidioidomycosis is caused by C immitis and C posadasii, 2 genetically distinct but morphologically identical species of a soil fungus endemic to certain arid-to-semiarid regions of the Western Hemisphere. The ecologic niche of Coccidioides is in the desert Southwest. This zone is characterized by low elevations (below 3700 ft), scant rainfall (5-20 in/y), mild winters (40-54°F) and hot summers, and sandy alkaline soil with increased salinity. [6, 12, 13]

Desert Southwest zones are found in areas of the Western Hemisphere from latitudes 40° north to 40° south. [2, 14, 15] The endemic areas for Coccidioides in the United States include Arizona, south central California (San Joaquin Valley), Nevada, New Mexico, certain parts of Utah, and the western half of Texas.

Other endemic areas are the regions of Mexico that border the western United States. The fungi also are endemic to some Central American countries, including Guatemala, Honduras, and Nicaragua. Certain desert regions of South America (Brazil, Argentina, Paraguay, Venezuela) also are endemic.

C immitis is largely limited to the San Joaquin Valley. C posadasii is found in the other areas of Coccidioides endemicity. The manifestations of infection with either organism are assumed to be identical.

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