Cryptococcus is a yeast that has a capsule surrounding the cell. In the yeast classification system, Cryptococcus is a member of the Phylum Basidimycota, Subphylum Basidimycotina, Order Sporidiales, and Family Sporidiobolaceae.

There are 37 species in the genus Cryptococcus. One of these, only one species is disease-causing, Cryptococcus neoformans. There are three so-called varieties of this species, based on antigenic differences in the capsule, some differences in biochemical reactions such as the use of various sugars as nutrients, and in the shape of the spores produced by the yeast cells. The varieties are Cryptococcus neoformans var. gatti, grubii, and neoformans. The latter variety causes the most cryptococcal infections in humans.

Cryptococcus neoformans has a worldwide distribution. It is normally found on plants, fruits and in birds, such as pigeons and chicken. Transmission via bird waste is a typical route of human infection.

Cryptococcus neoformans causes...