Bacillus anthracis Spores in a Contaminated US Senate Office.

Context: Bioterrorist attacks involving letters and mail-handling systems in Washington, DC, resulted in Bacillus anthracis (anthrax) spore contamination in the Hart Senate Office Building and other facilities in the US Capitol's vicinity. Objective: To provide information about the nature and extent of indoor secondary aerosolization of B anthracis spores. Design: Stationary and personal air samples, surface dust, and swab samples were collected under semiquiescent (minimal activities) and then simulated active office conditions to estimate secondary aerosolization of B anthracis spores. Nominal size characteristics, airborne concentrations, and surface contamination of B anthracis particles (colony-forming units) were evaluated. Results: Viable B anthracis spores reaerosolized under semiquiescent conditions, with a marked increase in reaerosolization during simulated active office conditions. Increases were observed for B anthracis collected on open sheep blood agar plates (P<.001) and personal air monitors (P = .01) during active office conditions. More than 80% of the B anthracis particles collected on stationary monitors were within an alveolar respirable size range of 0.95 to 3.5 µm. Conclusions: Bacillus anthracis spores used in a recent terrorist incident reaerosolized under common office activities. These findings have important implications for appropriate respiratory protection, remediation, and reoccupancy of contaminated office environments. [ABSTRACT FROM AUTHOR]