Distribution of airborne influenza virus and respiratory syncytial virus in an urgent care medical clinic.

BACKGROUND: Considerable controversy exists with regard to whether influenza virus and respiratory syncytial virus (RSV) are spread by the inhalation of infectious airborne particles and about the importance of this route, compared with droplet or contact transmission. METHODS: Airborne particles were collected in an urgent care clinic with use of stationary and personal aerosol samplers. The amounts of airborne influenza A, influenza B, and RSV RNA were determined using real-time quantitative polymerase chain reaction. Health care workers and patients participating in the study were tested for influenza. RESULTS: Seventeen percent of the stationary samplers contained influenza A RNA, 1% contained influenza B RNA, and 32% contained RSV RNA. Nineteen percent of the personal samplers contained influenza A RNA, none contained influenza B RNA, and 38% contained RSV RNA. The number of samplers containing influenza RNA correlated well with the number and location of patients with influenza (r= 0.77). Forty-two percent of the influenza A RNA was in particles < or = 4.1 microm in aerodynamic diameter, and 9% of the RSV RNA was in particles < or = 4.1 microm. CONCLUSIONS: Airborne particles containing influenza and RSV RNA were detected throughout a health care facility. The particles were small enough to remain airborne for an extended time and to be inhaled deeply into the respiratory tract. These results support the possibility that influenza and RSV can be transmitted by the airborne route and suggest that further investigation of the potential of these particles to transmit infection is warranted.

A numerical study of worker exposure to a gaseous contaminant: variations on body shape and scalar transport model.

Three-dimensional computational fluid dynamics simulations are used to investigate the distribution and level of contaminant concentrations in the true breathing zone (at the nose and mouth) when toxic airborne contaminants are released within an arm's length in front of the worker who has his back to the airflow. The effects of different body shapes on fluid flow and concentration patterns around the body in a wind tunnel were evaluated and clarified that a sharp body or a block may not be a good surrogate for the human form in consideration of occupational and environmental health studies. The comparison of the concentration field calculated with the Eulerian and Lagrangian methods revealed that the Eulerian method has a more diffusive nature than the Lagrangian method. The concentrations at different locations were also compared to determine the optimum sampling location. It was found that the concentration at the breathing zone may be significantly different from the one at the chest area. The influence of the heat flux from the body was studied at two different Reynolds numbers. Predictions indicate that the heat flux may have a significant impact on exposure especially when the convection induced by buoyancy dominates the flow.