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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.

Beijing, Mar 12: The number of fresh infections at the epicentre of China's coronavirus epidemic dropped to a new low on Thursday but the country imported more cases from abroad.

Another 11 people died, the lowest daily increase since late January, bringing the toll in China to 3,169 deaths, according to the National Health Commission.

There were only eight new cases in Wuhan, the city where the virus first emerged in December before growing into a national crisis and a pandemic.

It is the first time that new cases in Wuhan, the capital of Hubei province, have fallen to single-digits since figures started to be reported in January.

With cases falling dramatically in recent weeks, authorities this week began to loosen some restrictions on Hubei's 56 million people, who have been under quarantine since late January.

Healthy people living in low-risk areas of the province can now travel within Hubei. While Wuhan is not included, some of the city's companies were told they could resume work.

Only one other non-imported case was recorded elsewhere in the country.

But as global hotspots emerge elsewhere, China fears that cases arriving from abroad could undermine its progress.

On Thursday there were six more imported cases reported, bringing the total of infections from overseas to 85, health officials said.

Beijing has ordered a 14-day quarantine for everyone arriving in the city from any country.

Travellers flying into Beijing Capital International Airport from high-risk countries are now handled separately from other passengers.

A total of 80,793 people have now been infected in China.

President Xi Jinping said this week during his first visit to Wuhan since the crisis erupted that the spread of the disease has been "basically curbed" in China.

Tokyo, Mar 4: Takeda Pharmaceutical Co said on Wednesday it was developing a drug to treat COVID-19, the flu-like illness that has struck more than 90,000 people worldwide and killed over 3,000.

The Japanese drugmaker is working on a plasma-derived therapy to treat high-risk individuals infected with the new coronavirus and will share its plans with members of the U.S. Congress on Wednesday, it said in a statement.

Takeda is also studying whether its currently marketed and pipeline products may be effective treatments for infected patients.

"We will do all that we can to address the novel coronavirus threat...(and) are hopeful that we can expand the treatment options," Rajeev Venkayya, president of Takeda's vaccine business, said in the statement.

Takeda said it was in talks with various health and regulatory agencies and healthcare partners in the United States, Asia and Europe to move forward its research into the drug.

Its research requires access to the blood of people who have recovered from the respiratory disease or who have been vaccinated, once a vaccine is developed, Takeda said.