Detection of Infectious Influenza Virus in Cough Aerosols Generated in a Simulated Patient Examination Room

Bioaerosols are generated during wastewater treatment (eg Wang et al., 2018) and personnel working in public are also at risk of infection through inhaling aerosolised virus. This study describes the working efficacy of a N95 respirator mask (left image) or a surgical mask (right image).

The Experiment: A mechanical dummy which coughed infectious influenza virus was placed in a room (humidity 44-63%) with another ‘breathing’ dummy which contained aerosol samplers in its ‘mouth’. Health, clinical and other workers do not seal the masks to their faces (right image), and the dummy modelled this . Virus was extracted from the samplers, surgical gloves, masks and respirator masks, then cultured to identify infectious virus. Extracts of the viral DNA were subjected to qRTPCR to facilitate quantification of the infectious virus.

Results: the N95 mask prevented 67% of the infectious virus entering the dummy’s mouth, whereas the surgical mask blocked entry to 57%. Infectious virus was found in the outer water-repellent and middle filtering layers of both types of mask, and on the surfaces of surgical gloves attached to the head of the ‘breathing’ dummy.

Conclusions: Wearing surgical masks reduces but does not remove risk of infection. This is because the way these masks are worn leaves gaps between the wearers face and the mask which allow entry of aerosol particles, even when the masks are tied tightly to the face.

REFERENCE:

John D. Noti, William G. Lindsley, Francoise M. Blachere, Gang Cao, Michael L. Kashon, Robert E. Thewlis, Cynthia M. McMillen, William P. King, Jonathan V. Szalajda, and Donald H. Beezhold (2012) Clinical Infectious Diseases 54(11):1569–77.

https://DOI: 10.1093/cid/cis237

Published by Fiona Young

Adjunct Associate Professor, College of Medicine and Public Health, Flinders University, Adelaide, SA. She taught and researched in the disciplines of Medical and Environmental Biotechnology, with a focus on toxicology and mammalian cell culture using 3D systems to examine effects of toxins and pollutants on human cells.

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