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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.

New Delhi, May 25: Union Home Minister Amit Shah on Monday extended his greetings on the occasion of Eid-ul-Fitr and wished that the festival will bring peace and happiness to all.

"Extend my warm greetings on the occasion of Eid-ul-Fitr. May this festival bring peace and happiness in everyone's life," Shah tweeted.

Eid-ul-Fitr is being celebrated across the country on Monday.

New Delhi, Mar 5: The primary classes of all schools in the national capital will remain closed till March 31 to prevent a possibility of spread of coronavirus, Deputy Chief Minister Manish Sisodia announced on Thursday.

According to Directorate of Education (DoE) officials, while elaborate guidelines have been issued about preventive measures for coronavirus, students of nursery and primary classes are too young to understand the risk, making them more prone to infectious diseases.

Sisodia, who also holds the education portfolio, tweeted, "As a precautionary measure to prevent the possibility of spread of COVID-19 amongst our children, Delhi Government has directed the immediate closure of all primary schools (Govt/ aided/ private/MCD/NDMC) till 31/3/20(sic)."

A senior DoE official said, "Elaborate guidelines have already been issued. However, students of nursery and primary classes are too young to understand the risks associated with COVID-19. Thus they are more prone to infectious diseases and mingle around with classmates more often."

"It will be good if they are trained in the do's and dont's under the care and supervision of their parents at home. However, students of classes other than primary will continue to come to schools or examination centres for writing their examination as per schedule. The teaching, as well as non-teaching staff, will also attend regular school," the official said.

As of now, the number of confirmed COVID-19 cases in the country stands at 30, including 16 Italian tourists. The figure includes the first three cases reported from Kerala last month who have already been discharged following recovery.

Alerted by the coronavirus case reported in Delhi-NCR, schools in the region have sent out advisories to parents suggesting that they do not send their wards to attend classes even in case of mild cough or cold, and saying that they may declare holidays if the need arises. A few schools have announced already holidays and others have advanced their spring break.