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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, Jun 17: The United States is closely monitoring the situation following a fierce clash between Indian and Chinese forces in eastern Ladakh and hopes that the differences will be resolved peacefully, officials said here.

Twenty Indian Army personnel including a colonel were killed in the clash with Chinese troops in the Galwan Valley in eastern Ladakh on Monday night, the biggest military confrontation in over five decades that has significantly escalated the already volatile border standoff in the region.

"We are closely monitoring the situation between Indian and Chinese forces along the Line of Actual Control," a State Department spokesperson said.

"We note the Indian military has announced that 20 soldiers have died, and we offer our condolences to their families," the official said.

Both India and China have expressed their desires to de-escalate and the US supports a peaceful resolution of the current situation, the spokesperson said.

"During their phone call on June 2, 2020, President Donald Trump and Prime Minister Narendra Modi had discussed the situation along the India-China border," the official added.

As the deadly coronavirus has spread worldwide, it has carried with it xenophobia -- and Asian communities around the world are finding themselves subject to suspicion and fear.

When a patient on Australia's Gold Coast refused to shake the hand of her surgeon Rhea Liang, citing the virus that has killed hundreds, the medic's first response was shock.

But after tweeting about the incident and receiving a flood of responses, the respected doctor learned her experience was all too common.

There has been a spike in reports of anti-Chinese rhetoric directed at people of Asian origin, regardless of whether they have ever visited the centre of the epidemic or been in contact with the virus.

Chinese tourists have reportedly been spat at in the Italian city of Venice, a family in Turin was accused of carrying the disease, and mothers in Milan have used social media to call for children to be kept away from Chinese classmates.

In Canada, a white man was filmed telling a Chinese-Canadian woman "you dropped your coronavirus" in the parking lot of a local mall.

In Malaysia, a petition to "bar Chinese people from entering our beloved country" received almost 500,000 signatures in one week.

The incidents are part of what the Australasian College for Emergency Medicine has described as "misinformation" which it says is fuelling "racial profiling" where "deeply distressing assumptions are being made about 'Chinese' or 'Asian-looking' people." Disease has long been accompanied by suspicions of foreigners -- from Irish immigrants being targeted in the Typhoid Mary panic of 1900s America to Nepali peacekeepers being accused of bringing cholera to earthquake-struck Haiti in the last decade.

"It's a common phenomenon," said Rob Grenfell, director of health and biosecurity for Australia's science and research agency CSIRO.

"With outbreaks and epidemics along human history, we've always tried to vilify certain subsets of the population," he said, comparing the behaviour to 1300s plague-ridden medieval Europe, where foreigners and religious groups were often blamed.

"Sure it emerged in China," he said of the coronavirus, "but that's no reason to actually vilify Chinese people." In a commentary for the British Medical Journal, doctor Abraar Karan warned this behaviour could discourage people with symptoms from coming forward.

Claire Hooker, a health lecturer at the University of Sydney, said the responses from governments may have compounded prejudice.

The World Health Organisation has warned against "measures that unnecessarily interfere with international travel and trade", but this has not stopped scores of countries from introducing travel bans.

The tiny Pacific nation of Micronesia has banned its citizens from visiting mainland China altogether.

"Travel bans respond largely to people's fears," said Hooker, and while sometimes warranted, they often "have the effect of cementing an association between Chinese people and scary viruses".

Abbey Shi, a Shanghai-born student in Sydney, said the attitude shown by some of her peers has "become almost an attack on students who are Chinese".

While Australia's conservative government has banished its citizens returning from Wuhan -- the central Chinese city at the epicentre of the virus -- to a remote island for quarantine, thousands of students still stuck in China risk their studies being torpedoed.

"Right now it looks like they have to miss the semester's start and potentially the whole year, because of the way the courses are set up," Shi said.

According to Hooker, studies in Toronto on the impact of Severe Acute Respiratory Syndrome, or SARS -- another global coronavirus outbreak in 2002 -- showed the impact of xenophobic sentiment often lasted much longer than the public health scare.

"While there may be a cessation of direct forms of racism as news about the disease dies down, it takes quite a bit of time for economic recovery and people continue to feel unsafe," she said.

People may not rush back to Chinese businesses or restaurants, and may even heed some of the more outlandish viral social media disinformation -- such as one popular post imploring people to avoid eating noodles for their own safety.

"In one sense you might think the effects lasted from the last coronavirus to this one because the representation as China being a place where diseases come from has been persistent," Hooker said.