Mucor contains an estimated 40 species. Members of the Mucor genus can be found living all over the world in a wide variety of environments, from the forest to the carpets of homes and businesses. In Northern Europe especially, Mucor species are ubiquitous indoors and can contribute to mold allergies in sensitive individuals. Some species cause diseases in humans, while others are known plant pathogens.

Fungi in this genus grow in the form of a white to gray mold which develops into a fluffy mass. The mold can grow on living and dead plants and in the soil. Mucor species are very aggressive and they will quickly overrun an environment, dominating other fungi. The mold grows and spreads quickly, making it difficult for slower-growing fungi to compete.

Given the ubiquitous nature of these fungi, most humans are exposed to these organisms on a daily or weekly basis. However, they rarely cause disease because of the low virulence of the organisms and instead mainly affect individuals with immunocompromising conditions. Immunocompromised hosts include the following: poorly controlled diabetes mellitus (especially with ketoacidosis), those receiving glucocorticosteroids, those who have neutropenia in the setting of hematologic or solid malignancy, who have undergone transplantation, who have iron overload, and who have burns are at risk for disease. The primary way of acquiring infection is via inhalation; other routes include ingestion and traumatic inoculation. When spores are deposited in the nasal turbinates, rhinocerebral disease develops; when spores are inhaled into the lungs, pulmonary disease develops; when ingested, GI disease ensues; and when the agents are introduced through abraded skin, cutaneous disease develops.