Surgical face masks worn by patients with multidrug-resistant tuberculosis: impact on infectivity of air on a hospital ward.

Rationale: Drug-resistant tuberculosis transmission in hospitals threatens staff and patient health. Surgical face masks used by patients with tuberculosis (TB) are believed to reduce transmission but have not been rigorously tested.

Objectives: We sought to quantify the efficacy of surgical face masks when worn by patients with multidrug-resistant TB (MDR-TB).

Natural infection of guinea pigs exposed to patients with highly drug-resistant tuberculosis.

A natural TB infection model using guinea pigs may provide useful information for investigating differences in transmission efficiency and establishment of active disease by clinical TB strains in a highly susceptible host under controlled environmental conditions. We sought to examine the capacity of naturally transmitted multidrug-resistant Mycobacterium tuberculosis to establish infection and produce active disease in guinea pigs. Guinea pigs were continuously exposed for 4 months to the exhaust air of a 6-bed multidrug-resistant tuberculosis inpatient hospital ward in South Africa.

Role of absolute humidity in the inactivation of influenza viruses on stainless steel surfaces at elevated temperatures.

Influenza virus has been found to persist in the environment for hours to days, allowing for secondary transmission of influenza via inanimate objects known as fomites. We evaluated the efficacy of heat and moisture for the decontamination of surfaces for the purpose of preventing of the spread of influenza. Aqueous suspensions of influenza A virus were deposited onto stainless steel coupons, allowed to dry under ambient conditions, and exposed to temperatures of 55 degrees C, 60 degrees C, or 65 degrees C and relative humidity (RH) of 25%, 50%, or 75% for up to 1 h.

Inactivating influenza viruses on surfaces using hydrogen peroxide or triethylene glycol at low vapor concentrations.

Background: Surfaces in congregate settings, such as vehicles used for mass transportation, can become contaminated with infectious microorganisms and facilitate disease transmission. We disinfected surfaces contaminated with H1N1 influenza viruses using hydrogen peroxide (HP) vapor at concentrations below 100 ppm and triethylene glycol (TEG)-saturated air containing 2 ppm of TEG at 25 degrees C.

Methods: Influenza viruses in aqueous suspensions were deposited on stainless-steel coupons, allowed to dry at ambient conditions, and then exposed for up to 15 minutes to 10 to 90 ppm of HP vapor or TEG-saturated air.

Inactivation of poxviruses by upper-room UVC light in a simulated hospital room environment.

In the event of a smallpox outbreak due to bioterrorism, delays in vaccination programs may lead to significant secondary transmission. In the early phases of such an outbreak, transmission of smallpox will take place especially in locations where infected persons may congregate, such as hospital emergency rooms. Air disinfection using upper-room 254 nm (UVC) light can lower the airborne concentrations of infective viruses in the lower part of the room, and thereby control the spread of airborne infections among room occupants without exposing occupants to a significant amount of UVC.

Characterization of UVC light sensitivity of vaccinia virus.

Interest in airborne smallpox transmission has been renewed because of concerns regarding the potential use of smallpox virus as a biothreat agent. Air disinfection via upper-room 254-nm germicidal UV (UVC) light in public buildings may reduce the impact of primary agent releases, prevent secondary airborne transmission, and be effective prior to the time when public health authorities are aware of a smallpox outbreak. We characterized the susceptibility of vaccinia virus aerosols, as a surrogate for smallpox, to UVC light by using a benchtop, one-pass aerosol chamber.

Fundamental factors affecting upper-room ultraviolet germicidal irradiation - part II. Predicting effectiveness.

Compared with increasing outdoor air ventilation rate, upper-room ultraviolet germicidal irradiation (UVGI) is an attractive technology for lowering the indoor concentration of airborne microorganisms and thereby reducing the risk of airborne transmission of disease. With relatively modest vertical air circulation, most of the air in a room can be irradiated in a relatively brief time period without noise or significant power consumption. The hypothesis tested in this study is that the efficacy of upper-room UVGI to inactivate or kill airborne infectious microorganisms can be determined from an index of UVGI effectiveness, a dimensionless parameter designed to characterize adequacy of vertical air circulation, amount of UVGI provided, and their interaction.

Fundamental factors affecting upper-room ultraviolet germicidal irradiation - part I. Experimental.

The objective of this research was to study the factors that relate to the effectiveness of upper-room ultraviolet germicidal irradiation for inactivating airborne microorganisms. The work was conducted in a room-sized chamber designed and furnished for investigations of this nature. Nebulized Serratia marcescens, Bacillus subtilis spores, and vaccinia virus were used as test aerosols.

Monitoring human exposures to upper-room germicidal ultraviolet irradiation.

After decades of neglect, the resurgence of tuberculosis in the United States between 1985 and 1992 renewed interest in the use of upper room ultraviolet germicidal irradiation to interrupt the transmission of airborne infections. More recently the bioterrorism threat and the appearance of new pathogens with the potential for airborne spread, such as severe acute respiratory syndrome (SARS), have stimulated installations of upper-room irradiation systems. The objective is to flood the entire volume of a room above 6.

Size and UV germicidal irradiation susceptibility of Serratia marcescens when aerosolized from different suspending media.

Experimental systems have been built in laboratories worldwide to investigate the influence of various environmental parameters on the efficacy of UV germicidal irradiation (UVGI) for deactivating airborne microorganisms. It is generally recognized that data from different laboratories might vary significantly due to differences in systems and experimental conditions. In this study we looked at the effect of the composition of the suspending medium on the size and UVGI susceptibility of Serratia marcescens in an experimental system built in our laboratory.

The application of ultraviolet germicidal irradiation to control transmission of airborne disease: bioterrorism countermeasure.

Bioterrorism is an area of increasing public health concern. The intent of this article is to review the air cleansing technologies available to protect building occupants from the intentional release of bioterror agents into congregate spaces (such as offices, schools, auditoriums, and transportation centers), as well as through outside air intakes and by way of recirculation air ducts. Current available technologies include increased ventilation, filtration, and ultraviolet germicidal irradiation (UVGI) UVGI is a common tool in laboratories and health care facilities, but is not familiar to the public, or to some heating, ventilation, and air conditioning engineers.

Laboratory chemical hoods: a historical perspective.

A historical review of laboratory fume hoods leads to a consideration of the current status of structural design, operating characteristics (with special reference to face velocity), safety (relative to standardized test results), energy conservation, and certification methods. Noteworthy are (1) the increasing complexity of instrumentation designed to assure full safety function plus airflow modulation to minimize energy consumption; (2) the extreme plasticity of accepted and recommended face velocity values; (3) the insensitivity of standardized hood test protocols to variations in face velocity; and (4) a serious lack of correlation between operator risk, face velocity, and standard hood test results. Safety considerations lead to the selection of laboratory fume hoods having the highest demonstrated containment capability.

Report of the Howard Hughes Medical Institute's workshop on the performance of laboratory chemical hoods.

The Howard Hughes Medical Institute sponsored a workshop on laboratory chemical hoods on June 8, 9, and 10, 1998, that brought together 24 experts in the field of laboratory chemical hoods to critically assess the information known about hood performance. Workshop participants developed 31 consensus statements that reflect their collective views on the body of knowledge or lack thereof, for laboratory chemical hoods. The consensus statements fall into four broad categories: (1) hood selection, use, and operation; (2) hood and laboratory design issues; (3) ventilation system design issues; and (4) hood performance testing.

The characterization of upper-room ultraviolet germicidal irradiation in inactivating airborne microorganisms.

In this study, we explored the efficacy of upper-room ultraviolet germicidal irradiation (UVGI) in reducing the concentration of Serratia marcescens and Mycobacterium bovis bacille Calmette-Guérin (BCG) aerosols in enclosed places. We constructed a facility (4.5 m x 3 m x 2.