Aspergillosis is an infection or an allergic response caused by a fungus of the Aspergillus type. It may play a role in allergy, but is best known for causing serious pulmonary infections in immunocompromised patients, e.g. those on chemotherapy.

Cryptococcus neoformans is a species of fungus that can live in both plants and animals. This species, also known as Filobasidiella (Cryptococcus) neoformans, belongs to the broad class of organisms called "club fungi" or Division Basidiomycota, which is one the five major types of fungi. More specifically, C. neoformans is a type of yeast, but of a very different type than the yeasts used for baking, as a picture of the organism suggests.