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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.

Geneva, May 27: The number of confirmed cases of COVID-19 worldwide has increased by nearly 100,000 over the past 24 hours to surpass 5.4 million, the World Health Organisation (WHO) said.

According to the WHO, the global case tally currently stands at 5,404,512 -- a rise by 99,780 over the past day.

The death count worldwide amounts to 343,514 -- an increase by 1,486.

Most cases of infection are recorded in the Americas -- 2,454,452, with 143,739 deaths.

Maryland, Jul 4: The total number of coronavirus cases worldwide has touched 11 million, according to the latest data by the Johns Hopkins University on Saturday.
More than 523,613 people have died globally due to the infection, according to the data compiled by the university.

Though the virus is believed to have emerged from the Chinese city of Wuhan, the United States is the worst-hit country from COVID-19, which was declared as a pandemic by the WHO on March 11.

At least 129,275 people have died in the US from the coronavirus, according to Johns Hopkins University's latest tally.
There are at least 2,786,178 cases of the disease in the country. The US has the highest number of cases in the world.

The second worst-hit country is Brazil, which has reported 1,496,858 lakh cases. The country's death toll stands at 61,884.

The countries around the world including the US, India, Denmark, and Italy have started the process of lifting the lockdown by easing restrictions despite the number of cases continues to rise.