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Controversy around airborne versus droplet transmission of respiratory viruses

implication for infection prevention

Shiu, Eunice Y.C.; Leung, Nancy H.L.; Cowling, Benjamin J.

Current Opinion in Infectious Diseases: August 2019 - Volume 32 - Issue 4 - p 372–379
doi: 10.1097/QCO.0000000000000563

Purpose of review Health agencies recommend transmission-based precautions, including contact, droplet and airborne precautions, to mitigate transmission of respiratory viruses in healthcare settings. There is particular controversy over the importance of aerosol transmission and whether airborne precautions should be recommended for some respiratory viruses. Here, we review the current recommendations of transmission-based precautions and the latest evidence on the aerosol transmission of respiratory viruses.

Recent findings Viral nucleic acids, and in some instances viable viruses, have been detected in aerosols in the air in healthcare settings for some respiratory viruses such as seasonal and avian influenza viruses, Middle East respiratory syndrome-coronavirus and respiratory syncytial virus. However, current evidences are yet to demonstrate that these viruses can effectively spread via airborne route between individuals, or whether preventive measures in airborne precautions would be effective.

Summary Studies that use transmission events as outcome to demonstrate human-to-human transmission over the aerosol route or quantitative measurement of infectious respiratory viruses in the air are needed to evaluate the infectiousness of respiratory viruses over the aerosol route. When a respiratory virus in concern only leads to disease with low severity, airborne precautions are not likely to be justified.

WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China

Correspondence to Dr Nancy H.L. Leung, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, 7 Sassoon Road, Pokfulam, Hong Kong Special Administrative Region, China. Tel: +852 3917 6757; fax: +852 2855 9528; e-mail:

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