Clinical disease resulting from fungal infection by either Coccidioides immitis or Coccidioides posadasii. The organism is endemic in the Americas and is sometimes known as San Joaquin Valley fever. Coccidioides exists in the environment, thriving in the soil, but assumes a dormant spore stage in dry conditions. These can be released in to the air during construction, excavation or earthquake. The air borne spores are inhaled such that respiratory disease is the commonest presentation.
In immunocompetent individuals, the primary respiratory infection ("primary respiratory coccidioidomycosis") may be asymptomatic or subclinical. Others will develop symptoms indistinguishable from other common respiratory tract infections and will recover with no complications. A more severe disease may occur in immunosuppressed individuals, e.g. in HIV/AIDS.
In about 5% of individuals, the organism is not cleared and can develop into lung nodules, with cavitation and possible progression into chronic respiratory coccidioidomycosis. The disease can also become systemic, with certain ethnic groups showing particular susceptibility.