Study on the interzonal migration of airborne infectious particles in an isolation ward using benign bacteria
Article first published online: 18 JUL 2012
© 2012 John Wiley & Sons A/S
Volume 23, Issue 2, pages 148–161, April 2013
How to Cite
Leung, W. T., Sze-To, G. N., Chao, C. Y. H., Yu, S. C. T. and Kwan, J. K. C. (2013), Study on the interzonal migration of airborne infectious particles in an isolation ward using benign bacteria. Indoor Air, 23: 148–161. doi: 10.1111/j.1600-0668.2012.00797.x
- Issue published online: 11 MAR 2013
- Article first published online: 18 JUL 2012
- Accepted manuscript online: 23 JUN 2012 09:55AM EST
- Received for review 20 December 2011. Accepted for publication 16 June 2012.
- Isolation ward;
- Containment effectiveness;
- Human movement;
- Interzonal migration
Abstract Negative pressure isolation wards are essential infection control facilities against airborne transmissible diseases. Airborne infectious particles are supposed to be contained in the isolation room. However, negative pressure may break down by door-opening action or by human movement. Understanding the interzonal transport of airborne infectious particles in the isolation wards can aid the design and operation strategy of isolation facilities. In this work, the interzonal migration of airborne infectious particles by human movement was studied experimentally in an isolation ward. Artificial saliva solution with benign E. coli bacteria was aerosolized to simulate bacterium-laden infectious particles. The interzonal migration of aerosolized bacteria was characterized by biological air sampling. Less than 1% of airborne infectious particles were transported to the higher pressure zone when door was closed. With human movement, 2.7% of the particles were transported from the anteroom to the corridor. From high-to-low pressure zones, as much as 20.7% of airborne infectious particles were migrated. Only a minimal amount of particles was transported from the corridor to the positive pressure nurses’ station. Infection risk of tuberculosis of the healthcare workers and other occupants in the isolation wards were also assessed based on the measured migration ratios.
Human movement is an important factor governing interzonal migration. It is the main cause of migration of airborne infectious particles to a relatively negative pressure zone. This study provides a set of experimentally obtained particle migration ratios by human movement. Other than serving as empirical data for further studies on the mechanics, these migration ratios can also be used to assess the infection risk for occupants in the isolation ward.