Cryptococcus neoformans
A basidiomycetous encapsulated fungal organism found worldwide, mainly around pigeon roosts and soil contaminated with decaying pigeon or chicken droppings. It is generally accepted that the organism enters the host by the respiratory route in the form of a dehydrated haploid yeast or as basidiospores. Hematogenously spreading to extrapulmonary tissues, its predilection for the brain means infected persons usually contract meningoencephalitis, which can be fatal.