CausesBy Mayo Clinic staff
The fungi that cause valley fever — Coccidioides immitis or Coccidioides posadasii — thrive in the arid desert soils of southern Arizona, Nevada, northern Mexico and California's San Joaquin Valley. They're also endemic to New Mexico, Texas, and parts of Central and South America — areas with mild winters and arid summers.
Like many other fungi, coccidioides species have a complex life cycle. In the soil, they grow as a mold with long filaments that break off into airborne spores when the soil is disturbed. The spores are extremely small, can be carried hundreds of miles by the wind and are highly contagious. Once inside the lungs, the spores reproduce, perpetuating the cycle of the disease.
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