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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, Mar 12: For the global economy, virus repercussions were profound, with increasing concerns of wealth- and job-wrecking recessions. U.S. stocks wiped out more than all the gains from a huge rally a day earlier as Wall Street continued to reel.

The Dow Jones Industrial Average dropped 1,464 points, bringing it 20% below its record set last month and putting it in what Wall Street calls a “bear market.” The broader S&P 500 is just 1 percentage point away from falling into bear territory and bringing to an end one of the greatest runs in Wall Street’s history.

WHO officials said they thought long and hard about labeling the crisis a pandemic — defined as sustained outbreaks in multiple regions of the world.

The risk of employing the term, Ryan said, is “if people use it as an excuse to give up.” But the benefit is “potentially of galvanizing the world to fight.”

Underscoring the mounting challenge: soaring numbers in the U.S. and Europe’s status as the new epicenter of the pandemic. While Italy exceeds 12,000 cases and the United States has topped 1,300, China reported a record low of just 15 new cases Thursday and three-fourths of its infected patients have recovered.

China’s totals of 80,793 cases and 3,169 deaths are a shrinking portion of the world’s more than 126,000 infections and 4,600 deaths.

“If you want to be blunt, Europe is the new China,” said Robert Redfield, the head of the U.S. Centers for Disease Control and Prevention.

With 12,462 cases and 827 deaths, Italy said all shops and businesses except pharmacies and grocery stores would be closed beginning Thursday and designated billions in financial relief to cushion economic shocks in its latest efforts to adjust to the fast-evolving crisis that silenced the usually bustling heart of the Catholic faith, St. Peter’s Square.