Aspergillosis is infection with a fungus called Aspergillus. This is found throughout the world in a variety of species, usually in decaying vegetation and soil. It is quite rare for anyone, including people with HIV, to experience problems from exposure to Aspergillus in cooler climates, but it is a more common opportunistic infection in hot climates. It has been reported that between 3 and 7% of people with HIV will develop aspergillosis in Brazil and Ivory Coast, for example. At one Spanish HIV / AIDS clinic, just over 1% of patients developed pulmonary (lung) aspergillosis between 1985 and 1998.

People who have neutropenia (a shortage of infection-fighting neutrophils), who have been taking steroids for a long time or who smoke marijuana may be at increased risk. People who have had PCP are also at increased risk, especially if the PCP resulted in cyst-like cavities in the lungs. Aspergillosis also seems to be more common in people with CMV disease.

Aspergillosis is a condition associated with advanced AIDS and average survival time was two to four months prior to the introduction of antiretroviral therapies. Among HIV-infected people with access to antiretroviral therapy, aspergillosis is now rarely seen. When aspergillosis does occur, the introduction of combination antiretroviral therapy or a change to the existing regimen has extended average survival time to 30 months (Moreno).