Why is coccidioidomycosis called valley fever?

Coccidioidomycosis is commonly known as valley fever because it is frequently found in the southwestern United States, particularly in the Central Valley of California and surrounding desert areas. The disease is caused by the inhalation of spores from the Coccidioides immitis and Coccidioides posadasii fungi, which are found in the soil of these regions.

The name "valley fever" is derived from the fact that the disease is most prevalent in the valleys and desert areas of the Southwest, where the fungi that cause it are most commonly found. The term has been used since at least the early 20th century and has become widely recognized as a common name for coccidioidomycosis.