Transport of Bacillus thuringiensis var. kurstaki from an Outdoor Release into Buildings: Pathways of Infiltration and a Rapid Method to Identify Contaminated Buildings

Abstract

Understanding the fate and transport of biological agents into buildings will be critical to recovery and restoration efforts after a biological attack in an urban area. As part of the Interagency Biological Restoration Demonstration (IBRD), experiments were conducted in Fairfax County, VA, to study whether a biological agent can be expected to infiltrate into buildings following a wide-area release. Bacillus thuringiensis var. kurstaki is a common organic pesticide that has been sprayed in Fairfax County for a number of years to control the gypsy moth. Because the bacterium shares many physical and biological properties with Bacillus anthracis, the results from these studies can be extrapolated to a bioterrorist release. In 2009, samples were collected from inside buildings located immediately adjacent to a spray block. A combined probabilistic and targeted sampling strategy and modeling were conducted to provide insight into likely methods of infiltration. Both the simulations and the experimental results indicate sampling entryways and heating, ventilation, and air conditioning (HVAC) filters are reasonable methods for "ruling in" a building as contaminated. Following a biological attack, this method is likely to provide significant savings in time and labor compared to more rigorous, statistically based characterization. However, this method should never be used to "rule out," or clear, a building.

Quantitative Analysis of Effects of UV Exposure and Spore Cluster Size on Deposition and Inhalation Hazards ofBacillusSpores

“…All of these environmental conditions, as well as others including wind speed, direction, topography, and turbulence, can be used to predict resulting clouds and areas of deposition of a released agent. When spraying Bacillus thuringiensis for pest control, releases of the insecticide typically occur at night with near zero solar UV, minimal wind speed, and large droplets; all in an attempt to minimize unintended dispersion of the released material (Van Cuyk et al 2011, 2012. Current threat assessment and hazard prediction models do not take into consideration particle size with respect to potential UV shielding effects, or self-encapsulation, which provide protection to spores within the middle of the cluster from UV exposure.…”

Detection of the Urban Release of a Bacillus anthracis Simulant by Air Sampling

“…This is not surprising given the proximity of this collector to the release location and known instances of bioagent transport into buildings. 19 However, the transport of a biological agent into the subway system has serious implications, including possible exposure of subway patrons who were not in the vicinity of the original release, and the need to decontaminate this critical urban infrastructure as part of restoration efforts. 20 The 2009 positive sample at PSU collector #4, inside a subway station 3.5 km downwind of the release, provides additional evidence of subway infiltration.…”

Considerations for estimating microbial environmental data concentrations collected from a field setting

“…Sampling of heating, ventilation, and air conditioning (HVAC) filters has also been recommended as a method to help determine indoor extent of contamination. 25 , 27 , 28 , 29 …”