Govt mulls to connect Madrasas to mainstream education

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, Jun 19: India on Friday added 13,586 new COVID-19 cases for the first time in a single day, pushing the tally to 3,80,532, while the death toll rose to 12,573 with 336 new fatalities, according to the Union Health Ministry data.

In some positive news, the number of recoveries crossed the two lakh-mark and stands at 2,04,710, while there are 1,63,248 total COVID-19 active cases, according to the updated official figure at 8 am.

One patient had migrated.

"Thus, around 53.79 percent patients have recovered so far," an official said.

The total number of confirmed cases include foreigners. 

India registered over 10,000 cases for the eighth day in a row.

Of the 336 new deaths reported till Friday morning, 100 were in Maharashtra, 65 in Delhi, 49 in Tamil Nadu, 31 in Gujarat, 30 in Uttar Pradesh, 12 each in Karnataka and West Bengal, 10 in Rajasthan, six in Jammu and Kashmir, five in Punjab, four each in Haryana and Madhya Pradesh, three in Telangana, two in Andhra Pradesh and one each in Assam, Jharkhand and Kerala.