Coccidioidomycosis, is it potentially fatal?

Often not fatal: For most otherwise healthy people coccidioidomycosis is a mild self-limited disease. Probably a surprisingly high percentage of the us population has been exposed without knowing it. Those with hiv/aids or some other immunodeficiency are at risk for more severe or disseminated disease, which can most certainly be fatal.

Yup: Especially in its disseminated and meningitis forms.