a number of different disease states in human beings that are caused by fungi (fungus) of the genus Aspergillus, especially A. fumigatus, A. flavus, and A. niger, and that produce a variety of effects on humans, ranging from no illness to allergic reactions to mild pneumonia to overwhelming generalized infection. The ubiquitous fungus Aspergillus is especially prevalent in the air. Inhalation of Aspergillus is common, but the fungus can also be introduced into the body through a cut or a surgical wound.

Characteristic symptoms of allergic bronchopulmonary aspergillosis, seen especially in patients with chronic pulmonary diseases, include a chronic, productive cough and purulent sputum occasionally tinged with blood and flecks of white or brownish mycelium (fungus material). Severe invasive aspergillosis is almost entirely limited to those whose immune systems (immune system) have been severely compromised, either by drug therapies or by disease—i.e., immunosuppressed patients. People with leukemia or other cancers (cancer) are unable to contain the organism in the lungs and may develop widespread disease involving the liver, kidneys, skin, and brain. Diagnosis is confirmed by microscopic identification of colonies and characteristic septate hyphae and sporulating structures. However, cultures of the fungus are usually not positive and sometimes can be made only by taking a tissue biopsy. Specific antifungal agents are available, but the invasive disease is rapidly fatal.