4.1 Droplets & aerosols

Droplets: small liquid drops that are generated by expiratory events such as coughing, sneezing, laughing, talking or even breathing. 

• Large droplets: usually brought down to ground under gravity and are transmitted over a limited distance (0.3-1.0 m).
• Small droplets: water content of large droplets may evaporate in air, producing smaller droplet that could travel up to 1.5 m.
• Droplet nuclei: water content of small droplets may evaporate in air, producing even smaller droplet nuclei that could then remain suspended in air and could be transmitted over a long distance (up to 50 m).

Aerosols: Suspensions of small liquid droplets or solid particles in air. 

References
Cowling BJ, Ip DKM, Fang VJ, et al. (2013): Aerosol transmission is an important mode of influenza A virus spread. Nat Commun 4: 1935-1935.

Further reading

4.1.1 Infectious Micro-droplets

• SARS-CoV-2 Coronavirus Micro-droplets – NHK World report