Outbreak of invasive Aspergillus infection in surgical patients, associated with a contaminated air-handling system

An outbreak of Aspergillus infection at a tertiary care hospital was identified among inpatients who had amputation wounds, peritonitis, allograft nephritis, or mediastinitis. During a 2-year period, 6 patients were identified, all of whom had Aspergillus species recovered from samples from normally sterile sites. All cases clustered in the operating theater during a single 12-day period. To assess operating theater air quality, particle counts were measured as surrogate markers for Aspergillus conidia. A substantial increase in the proportion of airborne particles ≥3 μm in size (range, 3-fold to 1000-fold) was observed in many operating rooms. A confined space video camera identified moisture and contamination of insulating material in ductwork and variable airflow volume units downstream of final filters. No additional invasive Aspergillus wound infections were identified after the operating theater air-handling systems were remediated, suggesting that this unusual outbreak was due to the deterioration of insulating material in variable airflow volume units.