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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.

Paris, Jun 28: More than 10 million cases of the new coronavirus have been officially declared around the world, half of them in Europe and the United States, according to an AFP tally on Sunday based on official sources.

At least 10,003,942 infections, including 498,779 deaths, have been registered globally.

Europe remains the hardest hit continent with 2,637,546 cases including 195,975 fatalities, while the United States has 2,510,323 infections including 125,539 deaths.

The rate of infections worldwide continues to rise, with one million new cases recorded in just six days.

The tallies, using data collected by AFP from national authorities and information from the World Health Organization (WHO), probably reflect only a fraction of the actual number of infections.

Many countries are testing only symptomatic or the most serious cases and some do not have the capacity to carry out widescale testing.

Washington, May 19: As the scientists across the world are struggling to develop a vaccine for combating coronavirus, US drugmaker Moderna announced on Monday (local time) that the phase I trial of its Covid-19 vaccine has shown positive early results.

The company is hopeful that it's vaccine could be available to the public as early as January next year. Several firms across the world are in the race to develop a vaccine for the deadly virus which has claimed over 3 lakh lives worldwide.

CNN citing Dr. Tal Zaks, Moderna's chief medical officer reported that "if future studies go well, the company's vaccine could be available to the public as early as January".

"This is absolutely good news and news that we think many have been waiting for for quite some time," Zaks was quoted as saying.

Moderna, based in Cambridge, Massachusetts announced that the vaccine developed neutralising antibodies to the virus at levels reaching or exceeding the levels seen in people who have naturally recovered from Covid-19, reported CNN.

These will be followed by phase 2 trials and phase 3 trials, which Moderna plans to start in July.

President Donald Trump had on Friday said that that the United States will be able to deliver a few hundred million doses of COVID-19 vaccine, under 'Operation Warp Speed', by the end of this year.

"I have very recently seen early data from a clinical trial with a coronavirus vaccine and this data made me feel even more confident that we'll be able to deliver a few hundred million doses of vaccine by the end of 2020 and we will do the best we can," Trump had said at a press conference at the White House on Friday.