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London, May 20: The current physical distancing guidelines of 6 feet may be insufficient to prevent COVID-19 transmission, according to a study which says a mild cough in low wind speeds can propel saliva droplets by as much as 18 feet.

Researchers, including those from the University of Nicosia in Cyprus, said a good baseline for studying the airborne transmission of viruses, like the one behind the COVID-19 pandemic, is a deeper understanding of how particles travel through the air when people cough.

In the study, published in the journal Physics of Fluids, they said even with a slight breeze of about four kilometres per hour (kph), saliva travels 18 feet in 5 seconds.

"The droplet cloud will affect both adults and children of different heights," said study co-author Dimitris Drikakis from the University of Nicosia.

According to the scientists, shorter adults and children could be at higher risk if they are located within the trajectory of the saliva droplets.

They said saliva is a complex fluid, which travels suspended in a bulk of surrounding air released by a cough, adding that many factors affect how saliva droplets travel in the air.

These factors, the study noted, include the size and number of droplets, how they interact with one another and the surrounding air as they disperse and evaporate, how heat and mass are transferred, and the humidity and temperature of the surrounding air.

In the study, the scientists created a computer simulation to examine the state of every saliva droplet moving through the air in front of a coughing person.

The model considered the effects of humidity, dispersion force, interactions of molecules of saliva and air, and how the droplets change from liquid to vapour and evaporate, along with a grid representing the space in front of a coughing person.

Each grid, the scientists said, holds information about variables like pressure, fluid velocity, temperature, droplet mass, and droplet position.

The study analysed the fates of nearly 1,008 simulated saliva droplets, and solved as many as 3.7 million equations.

"The purpose of the mathematical modelling and simulation is to take into account all the real coupling or interaction mechanisms that may take place between the main bulk fluid flow and the saliva droplets, and between the saliva droplets themselves," explained Talib Dbouk, another co-author of the study.

However, the researchers added that further studies are needed to determine the effect of ground surface temperature on the behaviour of saliva in air.

They also believe that indoor environments, especially ones with air conditioning, may significantly affect the particle movement through air.

This work is important since it concerns safety distance guidelines, and advances the understanding of the transmission of airborne diseases, Drikakis said.

Geneva, May 28: The global death toll from the novel coronavirus has risen over the past 24 hours by 5,581 to 349,095, the World Health Organization (WHO) said in its daily situation report.

The number of confirmed cases has increased by 84,314 to 5,488,825, the WHO said.

Most cases of infection are recorded in the Americas (North and South America) - 2,495,924, with 145,810 deaths. While Europe has reported 2,061,828 cases and 1,76,226 deaths so far.

As per WHO tally, the US has the highest number of cases in the world with 1,63,4010 infections.

The global health body declared the outbreak of the new coronavirus a pandemic on March 11.

Beijing, Jun 17: China said Wednesday it wanted to avoid further clashes with India along their border after the first deadly confrontation between the two nuclear powers in decades.

The two countries have traded blame for Monday's high-altitude brawl that left at least 20 Indian soldiers dead, with China refusing to confirm so far whether there were any casualties on its side.

Chinese foreign ministry spokesman Zhao Lijian insisted again Wednesday that it was Indian troops who illegally crossed the border and attacked the Chinese side.

This led to "a serious physical confrontation between both sides that caused deaths and injuries", Zhao said at a regular briefing, without providing more details about the casualties.

He said China urges India to "strictly restrain frontline troops, do not illegally cross the border, do not make provocative gestures, do not take any unilateral actions that will complicate the border situation".

But he added that the two sides "will continue to resolve this issue through dialogue and negotiations".

"We of course don't wish to see more clashes," Zhao said.