Fungi cause a number of infections in humans. Many of these cause only superficial infection, such as tinea pedis or athlete’s foot.

Many particularly nasty fungal infections, that can spread throughout the whole body, tend to be caused by thermally dimorphic fungi.

Thermally dimorphic fungi exist as a yeast form, or a mold form, depending on the temperature they are growing at. Common examples associated with pathological infection are: Histoplasma capsulatum, and Coccidiodes immitis.