Fungal Contamination in Public Buildings: Health Effects and Investigation Methods

2. Health Effects of Indoor Molds (Continued)

2.2.2 Invasive mycoses

Some fungi such as Aspergillus species are ubiquitous in the environment, and inhalation of their spores is very common. However, invasive mycoses (i.e. fungal infections) occur mostly in immunosuppressed patients. The most common pathogen is Aspergillus fumigatus (Bennett 1994). The incidence of invasive mycosis is increased in AIDS patients; an analysis of medical records of 35,232 HIV-infected patients who attended outpatients clinics in 10 US cities between 1990 and 1998 revealed that the incidence of invasive aspergillosis was 5.1 per 1000 (95% CI 2.8 to 7.3) in those with CD4 counts 50 to 99 cells/mm³ and 10.2 per 1000 in those with CD4 counts lower than 50 cells/mm³, compared to 1.0 per 1000 (95% CI 0.6 to 1.4) in those with CD4 counts equal to or higher than 200 cells/mm³ (Holding et al. 2000).

Some fungi such as Aspergillus species are ubiquitous in the environment, and inhalation of their spores is very common. However, invasive mycoses (i.e. fungal infections) occur mostly in immunosuppressed patients. The most common pathogen is Aspergillus fumigatus (Bennett 1994). The incidence of invasive mycosis is increased in AIDS patients; an analysis of medical records of 35,232 HIV- infected patients who attended outpatients clinics in 10 US cities between 1990 and 1998 revealed that the incidence of invasive aspergillosis was 5.1 per 1000 (95% CI 2.8 to 7.3) in those with CD4 counts 50 to 99 cells/mm³ and 10.2 per 1000 in those with CD4 counts lower than 50 cells/mm³, compared to 1.0 per 1000 (95% CI 0.6 to 1.4) in those with CD4 counts equal to or higher than 200 cells/mm³ (Holding et al. 2000).

Several outbreaks of invasive aspergillosis have been reported in hematology wards where neutropenic leukemia patients were housed. The risk of invasive aspergillosis in immunosuppressed patients was associated with the airborne concentrations of Aspergillus spores, and increased incidences have been observed following events resulting in higher Aspergillus counts in the air, such as construction or dysfunction in air filtration systems.

• From May 1981 to October 1985, 14 bone marrow transplant patients developed nosocomial Aspergillus infections out of 111 patients who underwent such transplants. Further analysis revealed that all these cases of infection occurred among the 74 patients housed outside a high-efficiency particulate air (HEPA) filtered environment, while none of the 39 patients housed in a HEPA-filtered environment developed aspergillosis. Only one of the 166 air samples collected in the HEPA-filtered environment (0.6%) was positive for Aspergillus, while 75 out of 466 samples collected elsewhere in the hospital (16.1%) and 13 out of 54 samples collected outside the hospital (24.1%) were positive (Sherertz et al. 1987).
• In 1993, six cases of aspergillosis were identified among the patients who attended the hematologyoncology ward of a pediatric hospital in Glasgow, United Kingdom, while only one case had been identified in that hospital over the five previous years. The outbreak investigation revealed that a contaminated vacuum cleaner used in the ward dispersed a bioaerosol; the Aspergillus concentration close to that vacuum cleaner was 62 CFU/m³ when it was in use, compared to 0 to 6 CFU/m³ elsewhere in the building (Anderson et al. 1996).
• In the hematology-oncology ward of a Montréal hospital, the incidence of invasive aspergillosis in patients with leukemia or bone marrow transplant identified as neutropenic rose to 9.88 per 1000 days at risk during construction activity (July 1989 to August 1992), compared to 3.18 per 1000 days at risk before the construction started (January to June 1989). Installation of wall-mounted portable HEPA filters and implementation of other infection control measures subsequently decreased the incidence of invasive aspergillosis to 2.91 per 1000 days at risk, even though the construction work continued (August 1992 to September 1993). The average concentration of Aspergillus in the air during the epidemic period was 6.77 CFU/m³, and no Aspergillus was recovered in air samples after the installation of the HEPA filter and the implementation of infection control measures (Loo et al. 1996).
• In the fall of 1993, in Israel, a nosocomial outbreak of invasive pulmonary aspergillosis occurred in leukemia patients treated in a regular ward with only natural ventilation during extensive hospital construction and indoor renovation. The infection among acute leukemia patients rose to 50%, and invasive pulmonary aspergillosis developed in 43% of acute leukemia patients during the next 18 months despite the administration of chemoprophylaxis. After that period, a new hematology ward was opened with an air filtration system with HEPA filters, and none of the acute leukemia or bone marrow transplantation patients who were hospitalized exclusively in the hematology ward developed invasive pulmonary aspergillosis, while 29% of acute leukemia patients who were housed in a regular ward, because of shortage of space in the new facility, still contracted invasive pulmonary aspergillosis. The average Aspergillus concentration was 0.18 spores/m³ in the new HEPA-ventilated hematological ward, while the average concentration in the regular ward during construction was 15 spores/m³ (Oren et al. 2001).

Community-acquired (i.e. out of hospital) opportunistic invasive aspergillosis is not as well documented, but some cases have been reported (Benoit et al. 2000; Chen et al. 2001). Immunosuppressed patients remain vulnerable to Aspergillus infections if exposed in the outpatient setting or at home after being released from hospital (VandenBergh et al. 1999)

2.2.3 Allergic bronchopulmonary mycoses and allergic fungal sinusitis

Fungi can colonize the lungs or nasal cavity of patients with underlying respiratory disease such as asthma or chronic rhinosinusitis. This condition is referred to as allergic bronchopulmonary mycosis when occurring in the lungs, and as allergic fungal sinusitis when taking place in the nasal cavity. Since Aspergillus species (especially Aspergillus fumigatus) are the most common etiologic agents causing allergic bronchopulmonary mycosis, this condition is commonly referred as allergic bronchopulmonary aspergillosis, or ABPA. Both conditions are characterized by eosinophilia and by the presence of non-invasive fungal hyphae in sputum or in nasal mucus (Hunninghake and Richerson 1994; Ponikau et al. 1999). Case reports have suggested a link between fungal counts in the air and the development of acute bronchopulmonary mycoses (Beaumont et al. 1984; Kramer et al. 1989; Ogawa et al. 1997).