The Changing Epidemiology and Diagnosis of Valley Fever

Coccidioidomycosis, commonly known as valley fever, is a disease caused by two species of fungi, Coccidioides immitis and Coccidioides posadasii. Coccidioidomycosis is often self-limiting; however, in some patients, the disease can rapidly progress to a severe and potentially life-threatening illness. Proper diagnostics for coccidioidomycosis are important because acute disease can manifest as community-acquired pneumonia, and can be misdiagnosed as a viral or bacterial infection. Improper diagnosis can lead to unnecessary antibacterial therapy and may encourage extra-pulmonary proliferation of the fungus, which then requires longer antifungal therapy. Although coccidioidomycosis is caused by two different species, in terms of symptoms, disease progression, or clinical diagnostics, there are no known differences between the species. Additionally, recent work has revealed that the distribution of the organism in the environment may be changing and that the organism exists in the environment beyond the region of high endemicity. Overall, disease incidence has risen, and it is not known if this represents a better reporting and diagnosis infrastructure, increased environmental load, or increasing pathogenicity. Discussed here are the most common approaches to diagnose coccidioidomycosis, as well as recent advances in our understanding of the changing epidemiology of the disease and the causative organism.