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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.

Washington DC, Feb 7: United States on Thursday asked all countries to speak out against mistreatment of Muslims living in China especially in Xinjiang region by Chinese authorities.

Alice G. Wells, Principal Deputy Assistant Secretary for the Bureau of South and Central Asian Affairs, while talking to reporters appreciated the steps taken by Central Asian states to ensure that no ethnic Kazakh, Uighur, Kyrgyz is refouled to China and that the human rights of individuals who reach Central Asia are observed.

"As a matter of principle we urge all countries, not just Central Asian countries, to speak out against human rights abuses that are evident against Muslims in all of China but certainly in Xinjiang. And the countries of Central Asia, several of the countries of Central Asia have deep first-hand knowledge of those abuses given the direct impact it has on their own populations who have loved ones, family members, that are swept up in these detention centers," Wells said.

"We appreciate steps by Central Asian states to ensure that no ethnic Kazakh, Uighur, Kyrgyz is refouled to China, that the human rights of individuals who reach Central Asia are observed. And we also appreciate I think what countries like Kazakhstan can do to promote the free and safe travel of compatriots, ethnic compatriots across the border," she added.

China has been accused of oppressing the Uighurs by sending them to mass detention camps, interfering in their religious activities and sending the community to undergo some form of forceful re-education or indoctrination. However, Pakistan has stayed mum over this issue.

As many as 1 million people, or about 7 per cent of Xinjiang's Muslim population, have been incarcerated in a sprawling network of "political re-education" camps, according to US and UN studies.

In 2018, the New York-based Human Rights Watch released a report accusing Beijing of a "systematic campaign of human rights violations" against Uighur Muslims in Xinjiang.

Beijing says its camps in Xinjiang are "vocational training centres."

Last year, several documents leaked revealed details about Beijing's fears about religious extremism and its wholesale crackdown on Uighurs.

The US had called on the Chinese government to "immediately release all of those who are arbitrarily detained and to end its draconian policies that have terrorised its own citizens in Xinjiang."