C. immitis lives in the soil in semiarid areas. Coccidioidomycosis is endemic to the southwestern United States, especially between the San Joaquin Valley in California and southwestern Texas; it’s also found in Mexico, Guatemala, Honduras, Venezuela, Colombia, Argentina, and Paraguay. It is transmitted by the inhalation of C. immitis spores either from the soil in these areas or from the wound dressings or plaster casts of infected people. The infection is most prevalent during warm, dry months.

Because of population distribution and an occupational link (it’s common in migrant farm laborers), coccidioidomycosis generally strikes Filipinos, Hispanics, Native Americans, and blacks. Of people who live in endemic regions, it is estimated that 10% to 50% will have evidence of Coccidioides exposure. In primary infections, the incubation period is 1 to 4 weeks. Coccidioidomycosis is not transmitted from person to person or from animals to people.

Patients diagnosed with coccidioidomycosis may develop complications, including bronchiectasis, osteomyelitis, meningitis, hepatosplenomegaly, and liver failure.

About 60% of C. immitis infections do not cause any symptoms. However, primary coccidioidomycosis can produce acute or subacute respiratory signs and symptoms (dry cough, pleuritic chest pain, and pleural effusion), fever, sore throat, dyspnea, chills, malaise, headache, and an itchy, macular rash. Chest pain, night sweats, and arthralgias can occur as well. Occasionally, the only sign is a fever that persists for weeks. From 3 days to several weeks after onset, some patients, particularly white women, may develop tender red nodules (erythema nodosum) on their legs, especially the shins, with joint pain in the knees and ankles. Generally, primary disease heals spontaneously within a few weeks.