Last reviewed 26 May 2020

Scientists have been looking at the ways in which weather conditions, such as a light breeze at an outdoor work site, could affect the risk associated with the coronavirus.

Airborne transmission of viruses such as in COVID-19 is not well understood, but a recent paper published in the journal Physics of Fluids, has found that a slight breeze of 4kph is able to make saliva travel 18 feet in just 5 seconds.

Saliva is a complex fluid, and it travels suspended in a bulk of surrounding air released by a cough.

To study how saliva moves through air, the authors created a computational fluid dynamics simulation that examined the state of every saliva droplet moving through the air in front of a coughing person.

Their simulation considered the effects of humidity, dispersion force, interactions of molecules of saliva and air, and how the droplets change from liquid to vapor and evaporate.

The findings imply that depending on the environmental conditions, the 2m social distance may not represent the limit of travel for droplets.

Senior author Dimitris Drikakis said, “Two metres is okay if there is no wind or very little, but beyond that situation, saliva droplets can travel a considerable distance.”

Commenting on the study, Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, said the study showed the importance of social distancing.

He added, “The most important point to take away from this paper is not that we need to change guidelines on social distancing, but that coughing is one of the best ways to spread infected droplets if you’re ill.

“So if you have a cough, stay at home until you’re better — and if you cough unexpectedly when you are out and about, cough into your elbow. Then go home, and stay there.”