Coccidioidomycosis fungus. Computer illustration of thick-walled arthroconidia and arthrospores from the fungus Coccidioides immitis. This fungus is found in desert and semi-arid regions, and is endemic to south-western USA, Mexico and South America. C. immitis is the causative agent of coccidioidomyocosis, also known as valley fever. The route of infection is almost always pulmonary, by inhalation of the spores. Agricultural workers are particularly at risk. Symptoms include a cough, chest pain, fever, rash and fatigue. Treatment is by antibiotic and antifungal drugs.