Aspergillus surveillance project at an urban hospital

Abstract

Aspergillus organisms are common in most ambient environments. Aspergillus organisms do not normally present a danger to healthy people, but have the potential to cause invasive disease and death in immune-compromised persons. Our department conducted a one-year surveillance study to evaluate the exposure potential at an urban, public hospital with four treatment areas for irnmunecompromised patients. Elements of the study included air sampling for Aspergillus organisms and other bio-aerosols, characterization of the ventilation and HVAC systems, characterization of dust collected during routine duct cleaning activities for the presence of an Aspergillus fumigatus protein, and considerations of duct cleaning and renovation/remodeling activities. The air sampling was conducted over a full year at six-day intervals. This study found that airborne Aspergillus, including the species implicated in infected hospital patients (A. fumigatus), was present in the air in all areas studied. The relationship between inside and outside concentrations of Aspergillus was very weak. A model of the penetration of organisms into the hospital showed that infiltration of outside air was not the primary source for the airborne Aspergillus levels found inside. Average airborne Aspergillus concentrations inside the hospital were dominated by several high concentration events. Although there appeared to be several sources inside, the dissemination of viable organisms occurred in specific time periods that may be directly related to operation of the air handling systems and outdoor weather. Duct cleaning and renovation/construction activities intermittently generated elevated concentrations of airborne bioaerosols.