Infection is caused by inhalation of the spores of the fungus, Coccidioides immitis, which is often found in desert regions. About 60% of infections cause no symptoms and are only recognized later by a positive coccidioidin skin test.

In the remaining 40% of cases, symptoms range from mild to severe. People with a compromised immune system tend to have more serious infections. Individuals with AIDS are at higher risk for pulmonary (lung) coccidioidomycosis, as well as for the disseminated (spread to many body systems) and cutaneous (skin) forms of the disease.

The disease can have an acute, chronic, or disseminated form. Acute pulmonary coccidioidomycosis is almost always mild, with few or no symptoms, and resolves without treatment. The incubation period is 7 to 21 days.

Acute coccidioidomycosis is rare. In any given year, about 3% of people who live in an area where coccidiomycosis is commonly seen will develop the disease.

Chronic pulmonary coccidioidomycosis can develop 20 or more years after initial infection which may not have been recognized, diagnosed, or treated at the time. Infections (lung abscesses) can form and rupture releasing pus (empyema) between the lungs and ribs (pleural space). This disorder is even less common than the acute form, however.

In disseminated disease, spread of infection to the bones, lungs, liver, meninges, brain, skin, heart, and pericardium (sac around the heart) may take place. Meningitis occurs in 30 to 50% of cases of disseminated disease. The course of the disease may be rapid for immunosuppressed patients.