Aspergillus fumigatus fungus in the lung, computer artwork. Aspergillus fumigatus is made up of fungal threads (hyphae, strands) with conidiophores (fruiting bodies, round clusters) at the tip. The conidiophores are made up of conidia (spores) that are dispersed on the wind. Inhalation of spores by people with a weakened respiratory system, such as asthmatics or those with cystic fibrosis, can result in an allergic reaction known as aspergillosis. A. fumigatus usually grows on decomposing organic matter. (KEYSTONE/SCIENCE PHOTO LIBRARY/AS&K VISUAL SCIENCE/SCIENCE PHOTO LIBRARY)