Efficacy of prevention by high-efficiency particulate air filtration or laminar airflow against Aspergillus airborne contamination during hospital renovation

OBJECTIVE: To evaluate efficacy of laminar airflow facilities plus high-eff iciency particulate air (HEPA) filtration and HEPA filtration alone in prev enting environmental Aspergillus contamination during hospital renovation. To show the usefulness of environmental surveillance to facilitate protecti on of patients at risk for invasive pulmonary aspergillosis. DESIGN: Prospective sampling of air and surfaces for Aspergillus conidia du ring 2-year period. SETTING: A hematological department adjacent to building renovation at a un iversity hospital. RESULTS: 1,047 air samples and 1,178 surface samples were collected from Ja nuary 1996 to December 1997. Significantly more air samples were positive f or Aspergillus species during the period of building renovation than during the periods before and after renovation in a unit without a protected air supply adjacent to the building work area (51.5% vs 31.7%; odds ratio [OR], 2.3; 95% confidence interval [CI95], 1.4-3.7; P<.001). A major increase in the frequency of positive air samples was also found in another adjacent u nit that was protected with HEPA filtration alone (from 1.8% to 47.5%; OR 4 8.9; CI95, 12-229; P<10(-7)). In addition, in this unit, the mean count of Aspergillus conidia in positive air samples increased significantly during construction (4 colony-forming units [CFU]/m(3) to 24.7 CFU/m(3); P=.04) an d the proportion of positive surface samples showed a significant increase during renovation (from 0.4% to 9.7%; OR, 28.3; CI95, 3.4-623; P=10(-4)). H owever, none of 142 air samples collected during renovation in the area pro tected with laminar airflow plus HEPA filtration showed Aspergillus conidia . In a unit distant from the building renovation site, the results of air a nd surface samples were not affected by renovation. CONCLUSION: This study showed a strong association between building renovat ion and an increase in environmental Aspergillus contamination. Results con firmed the high efficacy of laminar airflow plus HEPA filtration and a high air-change rate. Although filtration with HEPA was effective during normal conditions, it alone was unable to prevent the rise of Aspergillus contami nation related to building renovation. This study emphasized the necessity of an environmental survey of airborne contamination related to constructio n, to facilitate prevention of nosocomial aspergillosis outbreaks. A standa rdized protocol for aerobiological surveillance is needed.