After some initial confusion about the mode of transmission, it is now almost universally accepted that SARS-CoV-2 is an airborne virus. The United States Environmental Protection Agency summarises the issue as follows:
Spread of COVID-19 occurs via airborne particles and droplets. People who are infected with COVID can release particles and droplets of respiratory fluids that contain the SARS CoV-2 virus into the air when they exhale (e.g., quiet breathing, speaking, singing, exercise, coughing, sneezing). The droplets or aerosol particles vary across a wide range of sizes – from visible to microscopic. Once infectious droplets and particles are exhaled, they move outward from the person (the source). These droplets carry the virus and transmit infection. Indoors, the very fine droplets and particles will continue to spread through the air in the room or space and can accumulate.
The US EPA also points out:
Transmission of COVID-19 from inhalation of virus in the air can occur at distances greater than six feet. Particles from an infected person can move throughout an entire room or indoor space. The particles can also linger in the air after a person has left the room – they can remain airborne for hours in some cases.
While hand washing and good hygiene has many benefits, it will have limited impact in reducing the transmission of an airborne virus. The key methods of reducing transmission of an airborne virus are:
- Reduced mixing in crowded, indoor environments
- Ensuring adequate ventilation of indoor spaces
- Filtering the air using properly rated filters to extract viral particles
- Wearing high-quality masks
