Where do Coccidioides species primarily grow?

Coccidioides species, the fungi responsible for coccidioidomycosis or Valley fever, primarily thrive in soil, particularly in arid and semiarid regions of the southwestern United States, Mexico, and parts of Central and South America. The spores of Coccidioides are found in the soil where they can become airborne during disturbances, such as construction or wind erosion, leading to potential inhalation by individuals nearby.

The environmental conditions, such as temperature and moisture, significantly affect their growth, although they are primarily soil-dwelling organisms. This characteristic sets them apart from the other options listed, which do not represent the natural habitat or growth conditions for Coccidioides. Therefore, identifying soil as the primary growth medium for this fungus is fundamental for understanding its ecology and the means by which it can be transmitted to humans.