Physical distancing during the Covid-19 pandemic: Is a 2m gap enough?

Saliva droplets expelled by coughs can travel much farther than 2m in light winds, according to new findings.

That suggests physical distancing spaces of 2m may not be enough to prevent coronavirus transmission.

Airborne transmission of viruses, including the coronavirus that causes Covid-19, isn't well-understood. One way to learn more is to study how saliva particles travel through the air when people cough, explained researchers at the University of Nicosia in Cyprus.

"This work is vital, because it concerns health and safety distance guidelines, advances the understanding of spreading and transmission of airborne diseases, and helps form precautionary measures based on scientific results," said researcher Dimitris Drikakis, vice president for global partnerships at the university.

Shorter people more at risk?

Many factors affect how saliva droplets travel through the air, including their size and number, their interaction with one another and the surrounding air as they disperse and evaporate, and the humidity and temperature of the air, the researchers noted.

Such factors were taken into account when researchers created a computer simulation to assess how saliva moves through the air after a person coughs.

The simulation found that even with a slight breeze of 4km/h, saliva travels 5.5m in five seconds, according to the study in the journal Physics of Fluids.

"The droplet cloud will affect both adults and children of different heights," Drikakis said in a journal news release. "Shorter adults and children could be at higher risk if they are located within the trajectory of the travelling saliva droplets."

Further research is needed to determine how ground surface temperature affects airborne saliva. Also, airborne saliva should be assessed in indoor settings, where air conditioning has a significant impact on particle movement through air, the study authors said.

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