Definition of Coccidioidomycosis:

Coccidioidomycosis is infection with the spores of the fungus Coccidioides immitis.

Causes, incidence, and risk factors:

Infection is caused by inhaling the spores of the fungus Coccidioides immitis. This fungus 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 lung (pulmonary) coccidioidomycosis, as well as for the disseminated (spread to many organs) and skin (cutaneous) 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 goes away without treatment. The incubation period -- the time between breathing in the spores and becoming sick -- is 7 to 21 days.

Acute coccidioidomycosis is uncommon. 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.

In disseminated disease, infection may spread to the bones, lungs, liver, lining covering the brain and spinal cord (meninges), brain, skin, heart, and the sac around the heart (pericardium). Meningitis occurs in 30-50% of cases of disseminated disease. The disease may get worse quickly in immunosuppressed people.