Airborne Transmission

The spread of a virus from an infected person to an uninfected person, who is exposed to small virus-carrying droplets and aerosols that are suspended in the air over long distances (usually more than six feet/1.8 meters) and over time. When the exposed individual breathes in the virus-carrying air particles, they can become infected.

Respiratory droplets are produced when a person exhales (e.g. breathing, speaking, singing, coughing, and/or sneezing) and include a wide spectrum of sizes depending on how long they can remain suspended in the air. Droplet transmission is when an infection spreads through droplets which are larger than aerosols and occurs when someone is close to the infectious person, usually within six feet/1.8 meters, unlike aerosols which can float further away.

Available data shows that SARS-CoV-2 infection, like most other common respiratory viruses, spreads through droplets (and not aerosols) at close range. It’s not yet clear what proportion of SARS-CoV-2 infections are acquired through airborne transmission and how much virus one would have to be exposed to, to be infected. Airborne transmission of SARS-CoV-2 appears to occur in:

  • enclosed spaces when an infectious person is either in the same space as a susceptible person or transmission occurs shortly after the infectious person has left.
  • cases of prolonged exposure to respiratory particles, often generated by strong exhalation (e.g. shouting, singing, exercising) by an infectious person. This strong exhalation increases the concentration of suspended droplets in the air, and
  • spaces with inadequate ventilation where there is a build-up of suspended small respiratory droplets and particles.

 Fomite transmission is linked to airborne transmission of SARS-CoV-2.


Infectious Disease Respiration Transmission


AerosolDroplet transmissionFomite transmissionRespiratory dropletSARS-CoV-2