Because aspergillosis is not a reportable infection in the United States, the exact number of cases is difficult to determine. Milder, allergic forms of aspergillosis are more common than the invasive form of the infection.
Allergic bronchopulmonary aspergillosis (ABPA) likely affects between 1 and 15% of cystic fibrosis patients.1 One study calculated that 2.5% of adults who have asthma also have ABPA, which is approximately 4.8 million people worldwide.2 Of these 4.8 million people who have ABPA, an estimated 400,000 also have chronic pulmonary aspergillosis (CPA).2 Another 1.2 million people are estimated to have CPA as a sequel to tuberculosis,3 and over 70,000 people are estimated to have CPA as a complication of sarcoidosis.4
Invasive aspergillosis is uncommon and occurs primarily in immunocompromised people. The first population-based incidence estimates for invasive aspergillosis were obtained from laboratory surveillance conducted in the San Francisco Bay Area during 1992-1993 and suggested a yearly rate of 1 to 2 cases of aspergillosis per 100,000 population.5 However, the epidemiology of invasive Aspergillus infections has likely shifted since this time due to the increasing number of solid organ and stem cell transplant recipients and newer immunosuppressive agents.
Prospective surveillance among transplant recipients performed during 2001-2006 found that invasive aspergillosis was the most common type of fungal infection among stem cell transplant recipients6 and was the second-most common type of fungal infection among solid organ transplant recipients, with a 12-month cumulative incidence of 19%.7
Although most cases of aspergillosis are sporadic (not part of an outbreak), outbreaks of invasive aspergillosis occasionally occur in hospitalized patients. Invasive aspergillosis outbreaks are often found to be associated with hospital construction or renovation, which can increase the amount of airborne Aspergillus, resulting in respiratory infections or surgical site infections in high-risk patients.8,9 Outbreaks of primary cutaneous aspergillosis and central nervous system aspergillosis in association with the use of contaminated medical devices have also been described.10, 11 The incubation period for aspergillosis is unclear and likely varies depending on the dose of Aspergillus and the host immune response.
Allergic forms of aspergillosis such as allergic bronchopulmonary aspergillosis (ABPA) and allergic Aspergillus sinusitis are generally not life-threatening.
In contrast, although invasive aspergillosis is uncommon, it is a serious infection and can be a major cause of mortality in immunocompromised patients. For example, a large prospective study found that the one-year survival for people who had invasive aspergillosis was 59% among solid organ transplant recipients7 and 25% among stem cell transplant recipients.6