Discuss the important epidemiologic factors of cryptococcosis.

Cryptococcosis is caused by Cryptococcus neoformans, a ubiquitous encapsulated yeast found worldwide in the soil. Several strains are associated with pigeon and other avian excreta, and another strain is associated with eucalyptus trees. During the pre-AIDS era (prior to 1980), cryptococcal infections were rare and about 50% occurred in patients with lymphoreticular malignancies. Cryptococcosis is rare in immunocompetent patients, and patients at risk are those with impaired cellular immunity (advanced HIV patients, organ transplants, lymphoreticular malignancies, patients receiving corticosteroid therapy). The incidence of cryptococcosis is inversely proportional to the CD4 lymphocyte count. The prevalence of cryptococcosis in patients infected with HIV has declined with aggressive antiretroviral therapy. The mortality rate of untreated disseminated disease is 70% to 80%.

Perfect JR, Casadevall A: Cryptococcosis, Infect Dis Clin North Am 16:837–874, 2002.