Relationship between environmental fungal contamination and the incidence of invasive aspergillosis in haematology patients

Invasive aspergillosis (IA) is a major opportunistic infection in haematolo gy patients. Spore inhalation is the usual route of Aspergillus infection, suggesting a determining role of environmental contamination by spores in t he epidemiology of IA. We prospectively examined the relationship between e nvironmental contamination by Aspergillus and other fungal species and the incidence of invasive nosocomial aspergillosis (INA) in a bone marrow trans plantation unit and two haematology wards. During a four-year period, level s of air and surface fungal contamination were determined bi-monthly in pat ients' rooms (some equipped with HEPA filters and LAF systems), and various common sites in each ward (corridors, nursing stations, etc.). Results wer e compared to the incidence of INA. A total of 3100 air and 9800 surface sa mples were collected, and 79 cases of IA were diagnosed, of which 64 were p robably or possibly INA. Patterns of fungal contamination were comparable i n the three wards, with a gradient ranging from high levels in common sites to a virtual absence in rooms equipped with HEPA filters and LAF systems. Using a regression model, a significant relationship was found between the incidence of INA and the degree of fungal contamination of air and surfaces in conventional patient rooms (not equipped with HEPA) and common sites. T his study shows that in a non-epidemic setting, there is a significant rela tionship between environmental fungal contamination in haematology wards an d the incidence of INA. Our findings underline the importance of environmen tal surveillance and strict application of preventive measures. (C) 2001 Th e Hospital infection Society.