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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.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.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.