Controversy around airborne versus droplet transmission of respiratory viruses: implication for infection prevention

Abstract

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.

Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Personal Protective and Environmental Measures

“…It is essential to note that the mechanisms of person-to-person transmission in the community have not been fully determined. Controversy remains over the role of transmission through fine-particle aerosols (3,46). Transmission by indirect contact requires transfer of viable virus from respiratory mucosa onto hands and other surfaces, survival on those surfaces, and successful inoculation into the respiratory mucosa of another person.…”

ISIDOG Recommendations Concerning COVID-19 and Pregnancy

“…Another COVID-19 positive neonate showed stable vital signs, no fever or cough, but shortness of breath together with abnormal chest radiographs and abnormalities of liver function [56]. Considering that vertical intrauterine infection is unlikely, postpartum droplet or contact transmission from parents or other care takers to the neonate is the most plausible explanation [11,28,57]. Whether or not airborne transmission occurs is still not known [29,30].…”

“…International guidelines (CDC, ANZICS, WHO, RCOG) disagree on preventative measures to prevent airborne infection, whether or not to use FFP2/N95 ultra-filtration masks for health care providers in all contact with (possible) COVID-19 positive patients or only in aerosol producing procedures [2,3,[28][29][30][31]57,82,83]. In our opinion, health care providers working in close contact with COVID-19 suspected or positive patients should always wear full personal protective equipment (PPE) independent of performing "aerosol producing" procedures (waterproof gown, gloves, glasses or face shield) with FFP2 or N95 masks instead of surgical masks.…”

The SARS-CoV-2 outbreak from a one health perspective

“…Coronaviruses are airborne viruses that produce nosocomial infections [54]. They are mainly transmitted through droplet infection [55]. When the virus released from the animals or humans, it passes through the air and may drop on some services or objects.…”