Sources of Coccidioidomycosis (Valley Fever)

Coccidioides spores circulate in the air after contaminated soil and dust are disturbed by humans, animals, or natural disasters. The spores are too small to see without a microscope. When people breathe in these spores they are at risk of developing coccidioidomycosis. When Coccidioides spores enter the lungs, the change in temperature causes a physical change in the spore, and it develops into a spherule. When it ruptures, endospores are released, causing the infection to spread within the lungs or to other organs.

In rare cases, spores can enter the skin through cuts or abrasions and cause infection. Although animals can also develop coccidioidomycosis, the infection cannot be transmitted from person to person, animal to animal, or between people and animals.

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In the environment, Coccioides ssp. exists as a mold (1) with septate hyphae. The hyphae fragment into arthroconidia (2), which measure only 2–4 μm in diameter and are easily aerosolized when disturbed (3). Arthroconidia are inhaled by a susceptible host (4) and settle into the lungs. The new environment signals a morphologic change, and the arthroconidia become spherules (5). Spherules divide internally until they are filled with endospores (6). When a spherule ruptures (7) the endospores are released and disseminate within surrounding tissue. Endospores are then able to develop into new spherules (6) and repeat the cycle.