WHO acknowledges airborne spread of Covid-19 – suggests masking

    Geneva – Covid-19 airborne transmission is now considered one pathway for new infections, according to an advisory issued by the World Health Organization.

    BC’s Public Health Officer Dr. Bonnie Henry earlier had dismissed the possibility saying she believed measles and smallpox travelled great distances but not Covid-19 as suggested by 239 scientists who asked WHO to update its guidance because airborne spread is occurring. She described the open letter from the scientists as an attempt to “foment controversy.”

    However, the new brief from WHO states such airborne transmission can occur under some circumstances indoors.

    WHO summarized its findings as follows:

    • Understanding how, when and in what types of settings SARS-CoV-2 spreads between people is critical to develop effective public health and infection prevention measures to break chains of transmission.

    • Current evidence suggests that transmission of SARS-CoV-2 occurs primarily between people through direct, indirect, or close contact with infected people through infected secretions such as saliva and respiratory secretions, or through their respiratory droplets, which are expelled when an infected person coughs, sneezes, talks or sings.

    • Airborne transmission of the virus can occur in health care settings where specific medical procedures, called aerosol generating procedures, generate very small droplets called aerosols. Some outbreak reports related to indoor crowded spaces have suggested the possibility of aerosol transmission, combined with droplet transmission, for example, during choir practice, in restaurants or in fitness classes.

    • Respiratory droplets from infected individuals can also land on objects, creating fomites (contaminated surfaces). As environmental contamination has been documented by many reports, it is likely that people can also be infected by touching these surfaces and touching their eyes, nose or mouth before cleaning their hands.

    • Based on what we currently know, transmission of COVID-19 is primarily occurring from people when they have symptoms, and can also occur just before they develop symptoms, when they are in close proximity to others for prolonged periods of time. While someone who never develops symptoms can also pass the virus to others, it is still not clear to what extent this occurs and more research is needed in this area.

    • Urgent high-quality research is needed to elucidate the relative importance of different transmission routes; the role of airborne transmission in the absence of aerosol generating procedures; the dose of virus required for transmission to occur; the settings and risk factors for superspreading events; and the extent of asymptomatic and pre-symptomatic transmission.

    How to prevent transmission

    “The overarching aim of the Strategic Preparedness and Response Plan for COVID-19(1) is to control COVID-19 by suppressing transmission of the virus and preventing associated illness and death.”

    “To the best of our understanding, the virus is primarily spread through contact and respiratory droplets.

    “Under some circumstances airborne transmission may occur (such as when aerosol generating procedures are conducted in health care settings or potentially, in indoor crowded poorly ventilated settings elsewhere). 

    “More studies are urgently needed to investigate such instances and assess their actual significance for transmission of COVID-19.”

    To prevent transmission, WHO recommends a comprehensive set of measures including:

    • Identify suspect cases as quickly as possible, test, and isolate all cases (infected people) in appropriate facilities;

    • Identify and quarantine all close contacts of infected people and test those who develop symptoms so that they can be isolated if they are infected and require care;

    • Use fabric masks in specific situations, for example, in public places where there is community transmission and where other prevention measures, such as physical distancing, are not possible;

    • Use of contact and droplet precautions by health workers caring for suspected and confirmed COVID-19 patients, and use of airborne precautions when aerosol generating procedures are performed;

    • Continuous use of a medical mask by health workers and caregivers working in all clinical areas, during all routine activities throughout the entire shift;

    • At all times, practice frequent hand hygiene, physical distancing from others when possible, and respiratory etiquette; avoid crowded places, close-contact settings and confined and enclosed spaces with poor ventilation; wear fabric masks when in closed, overcrowded spaces to protect others; and ensure good environmental ventilation in all closed settings and appropriate environmental cleaning and disinfection.