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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.

Jun 12: The global number of COVID-19 cases has increased to over 7.5 million, while the death toll was nearing 421,000, according to the Johns Hopkins University.

As of Friday morning, the overall number of cases stood at 7,500,777, while the deaths increased to 420,993, the University's Center for Systems Science and Engineering (CSSE) revealed in its latest update.

The US continues with the world's highest number of confirmed cases and deaths at 2,022,488 and 113,803, respectively, according to the CSSE.

In terms of cases, Brazil comes in the second place with 802,828 infections.

This was followed by Russia (501,800), the UK (292,860), India (286,605), Spain (242,707), Italy (236,142), Peru (214,788), France (192,493), Germany (186,691), Iran (180,156), Turkey (174,023), Chile (154,092), Mexico (133,974), Pakistan (125,933) and Saudi Arabia (116,021), the CSSE figures showed.

Regarding fatalities, the UK continues in the second position after the US with 41,364 COVID-19 deaths, which also accounts for the highest number of fatalities in Europe.

The other countries with over 10,000 deaths are Brazil (40,919), Italy (34,167), France (29,349), Spain (27,136) and Mexico (15,944).

Washington, Feb 22: US President Donald Trump will raise the issue of religious freedom with Prime Minister Narendra Modi during his visit to India next week, the White House said on Friday, noting that the US has great respect for India's democratic traditions and institutions.

"President Trump will talk about our shared tradition of democracy and religious freedom both in his public remarks and then certainly in private. He will raise these issues, particularly the religious freedom issue, which is extremely important to this administration," a senior official told reporters in a conference call.

The official was responding to a question on whether the president was planning to speak to Modi on the Citizenship (Amendment) Act or the National Register of Citizens.

"We do have this shared commitment to upholding our universal values, the rule of law. We have great respect for India's democratic traditions and institutions, and we will continue to encourage India to uphold those traditions," the official said, requesting anonymity.

"And we are concerned with some of the issues that you have raised," the senior administration official said, in response to the question on CAA and NRC.

"I think the President will talk about these issues in his meetings with Prime Minister Modi and note that the world is looking to India to continue to uphold its democratic traditions, respect for religious minorities," the official said.

"Of course, it's in the Indian constitution -- religious freedom, respect for religious minorities, and equal treatment of all religions. So this is something that is important to the president and I'm sure it will come up," said the official.

Pointing out that India has a strong democratic foundation, the official said India is a country rich in religious, linguistic, and cultural diversity.

"In fact, it's the birthplace of four major world religions," the official noted.