The disease manifestations reflect the mode of transmission, with rhinocerebral and pulmonary diseases being the most common manifestations. Zygomycosis occurs only rarely in immunocompetent hosts. Host risk factors include diabetes mellitus, neutropenia, sustained immunosuppressive therapy, chronic prednisone use, iron chelation therapy, broad-spectrum antibiotic use, severe malnutrition, and primary breakdown in the integrity of the cutaneous barrier such as trauma, surgical wounds, needle sticks, or burns. Human zygomycosis caused by the Mucorales generally occurs in immunocompromised hosts as opportunistic infections. The spores from these molds are transmitted by inhalation, via a variety of percutaneous routes, or by ingestion of spores. do cause disease in animals, there is no longer sufficient evidence to suggest that they are true human pathogens. While disease is most commonly linked to Rhizopus spp., other organisms are also associated with human infection, including Mucor, Rhizomucor, Absidia, Apophysomyces, Saksenaea, Cunninghamella, Cokeromyces, and Syncephalastrum spp.
The majority of human illness is caused by the Mucorales.
There are two orders of Zygomycetes containing organisms that cause human disease, the Mucorales and the Entomophthorales. The Zygomycetes represent relatively uncommon isolates in the clinical laboratory, reflecting either environmental contaminants or, less commonly, a clinical disease called zygomycosis.
