Epidemiology of nosocomial fungal infections: invasive aspergillosis and the environment

The incidence rates of invasive aspergillosis have increased dramatically during the last two decades, and, despite all diagnostic and therapeutic efforts, outcome is often fatal. Therefore, preventive measures are of major importance in the control of invasive aspergillosis, and require full understanding of the epidemiology of this devastating disease. The environment has been suggested to play a crucial role in the epidemiology of invasive aspergillosis. Aspergillus spores are released in the air and may remain airborne for prolonged periods. As a result, spores are ubiquitously found in air and contaminate anything in contact with air. It has been hypothesized that the inhalation of airborne Aspergillus spores, either directly or through intermediate nasopharyngeal colonization, is a direct cause of pulmonary infection in immunocompromised patients. Recently, water has been suggested as an additional source of "airborne" Aspergillus spp. This review summarizes the current knowledge on the role of the environment in the epidemiology of invasive aspergillosis.