Fungi of the Aspergillus gene are World-wide in distribution and are present in soil and atmosphere.
There are about 600 species of Asperguillus organisms, but fewer than 10 are pathogenic to humans.
Of these A. fumigatus is the most common, A niger and A. flavus being much less frequent pathogens. The different species cannot be distinguished by morphology alone.
Aspergillus are responsible for several different forms of illness.
Pulmonary aspergillosis is acquired through the inhalation of the organism´s airbone spores. These spores are quite small, measuring less than 4μm in diameter, and are capable of reaching the most peripheral parts of the lungs.
The most characteristics presentation of the organism is that of thick, uniform, septate hyphae 3-6μm in width with 45ºangle.
A 56-year-old man developed pulmonary aspergillosis. Images from this case.