Severe acute respiratory syndrome (SARS) is characterized by a risk of nosocomial transmission; however, the risk of airborne transmission of SARS is unknown. During the Toronto outbreaks of SARS, we investigated environmental contamination in SARS units, by employing novel air sampling and conventional surface swabbing. Two polymerase chain reaction (PCR)-positive air samples were obtained from a room occupied by a patient with SARS, indicating the presence of the virus in the air of the room. In addition, several PCR-positive swab samples were recovered from frequently touched surfaces in rooms occupied by patients with SARS (a bed table and a television remote control) and in a nurses' station used by staff (a medication refrigerator door). These data provide the first experimental confirmation of viral aerosol generation by a patient with SARS, indicating the possibility of airborne droplet transmission, which emphasizes the need for adequate respiratory protection, as well as for strict surface hygiene practices.

On October 12, 2001, two envelopes containing Bacillus anthracis spores passed through a sorting machine in a postal facility in Washington, D.C. When anthrax infection was identified in postal workers 9 days later, the facility was closed. To determine if exposure to airborne B. anthracis spores continued to occur, we performed air sampling around the contaminated sorter. One CFU of B. anthracis was isolated from 990 L of air sampled before the machine was activated. Six CFUs were isolated during machine activation and processing of clean dummy mail. These data indicate that an employee working near this machine might inhale approximately 30 B. anthracis-containing particles during an 8-h work shift. What risk this may have represented to postal workers is not known, but the risk is approximately 20-fold less than estimates of sub-5 micron B. anthracis-containing particles routinely inhaled by asymptomatic, unvaccinated workers in a goat-hair mill.

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Chemiluminescent assays have been used to quantify phagocytic activity since 1972. In recent years these assays have been adapted to the 96-well microplate format as new luminometers have been developed. In this report we describe the optimization of a lucigenin enhanced phagocyte chemiluminescent assay using a Titertek Luminoskan. Factors such as cell concentration, serum concentration in the opsonization of the zymosan used and lucigenin concentration were all optimized in our assay. In addition we have found that some of the unique features of the Luminoskan, continuous microplate agitation during the assay and microplate temperature control up to 43 degrees C, also significantly enhanced the chemiluminescent response.

This report is the first detailed and quantitative study of potential mitigation procedures intended to deal with anthrax letters using a simulated anthrax letter release within an actual office building. Spore aerosols were created by opening letters containing 0.1 g of dry powdered Bacillus atrophaeus spores. Culturable aerosol samples were collected using slit-to-agar and filter-based samplers. Five test scenarios were designed to determine whether simple mitigation procedures or activities carried out by the person who opened the letter made a significant difference to aerosol concentrations in comparison to a control scenario where no activity took place. Surface contamination of the letter opener was measured at 10 body points for Scenarios 1 to 4. A sixth scenario, based on published Centers for Disease Control and Prevention anthrax letter response guidelines, used letters containing 1 g of spores. Results demonstrated that the spore aerosol spread throughout the building in less than 4.5 min. Potential mitigation techniques such as closing the office door or shutting off the ventilation system were not effective. Activities carried out by the letter opener including moving, walking to another location, and spraying water onto the contaminated desk with a hand sprayer all resulted in significantly higher aerosol concentrations in comparison to control. The potential total inhalational hazard for the letter opener during the five test scenarios ranged from 4.1 x 10(5) to 1.6 x 10(6) colony forming units (CFU) compared to 3.9 x 10(5) CFU for the control. Surface contamination of the letter opener (Scenarios 1 to 4) was highest on the right hip (4.8 x 10(4) to 1.0 x 10(5) CFU/cm(- 2)) and lowest on the right or left side of the head (2.2 x 10(2) to 3.7 x 10(3) CFU/cm(-2)). The statistically based methodology used in this study provided the means to objectively assess anthrax letter protocols to determine their effectiveness under realistic conditions. Potential mitigation procedures tested in this study did not reduce aerosol hazard or surface contamination.

Personal protection against infectious or toxic aerosols is a growing area of concern among many different occupational groups. Selection of appropriate respiratory protection should be based upon the level of risk present and the degree of protection afforded by the different types of protective masks available. In this study we have determined the relative protection factors for various commercial and military respiratory protective devices when challenged with a polydispersed submicron to micron sized particulate aerosol.