• The World Health Organisation (WHO) has formally acknowledged the possibility that the novel coronavirus can remain in the air in crowded indoor spaces, where “short-range aerosol transmission cannot be ruled out”.
What are aerosols?
• Aerosol is a term used to broadly refer to particles suspended in the air; they could include fine dust, mist, or smoke.
• In the context of transmission of viruses, as in this case, aerosols are read as micro droplets, much smaller (5 microns or lesser) than respiratory droplets, and take a longer time to drop to the floor.
• They will be expelled by people breathing, laughing or singing, as against respiratory droplets that are expelled with forceful acts such as sneezing or coughing.
What is Airborne transmission?
• Airborne transmission is defined as the spread of an infectious agent caused by the dissemination of droplet nuclei (aerosols) that remain infectious when suspended in air over long distances and time.
• It is different from droplet transmission as it refers to the presence of microbes within droplet nuclei, which are generally considered to be particles <5μm in diameter, can remain in the air for long periods of time and be transmitted to others over distances greater than 1 m.
How does it happen?
• Airborne transmission of SARS-CoV-2 can occur during medical procedures that generate aerosols (“aerosol generating procedures”).
• Theories suggest that 1) a number of respiratory droplets generate microscopic aerosols (<5 µm) by evaporating, and 2) normal breathing and talking results in exhaled aerosols.
• Thus, a susceptible person could inhale aerosols, and could become infected if the aerosols contain the virus in sufficient quantity to cause infection within the recipient.
Mains Paper 2: Health
Prelims level: airborne transmission
Mains level: Risking from airborne transmission of COVID-19