Coccidioides immitis (Coccidiomycosis)
(histological sections of lung tissue)

Coccidioides immitis is a soil dwelling fungus that generally lives in warm, arid climates. Spores may become airborne and, when inhaled by susceptible individuals, may develop into multicellular spherules in lung tissue. These spherules gradually increase in size and then burst to release endospores which themselves develop into more spherules. The pneumonic disease is termed "Valley Fever." The disease is not transmissible between humans.