US' new visa screening may seek applicants' social media info

London, Apr 27: British Prime Minister Boris Johnson returns to work on Monday more than three weeks after being hospitalised for the coronavirus and spending three days in intensive care.

Johnson, one of the highest-profile people to have contracted the virus, returned to 10 Downing Street on Sunday evening and will chair a meeting on Monday morning of the coronavirus "war cabinet", his colleagues confirmed.

Dominic Raab, the foreign secretary who has deputised in Johnson's absence, told the BBC on Sunday that his return would be a "boost for the government and a boost for the country".

Raab also claimed the prime minister was "raring to go".

Johnson, 55, was admitted to hospital on April 5 suffering from "persistent symptoms" of the deadly disease.

His condition worsened and he later admitted after being put in intensive care that "things could have gone either way".

He was discharged on April 12 and has been recuperating at his official residence, west of London.

In a video message after leaving hospital, Johnson thanked "Jenny from New Zealand and Luis from Portugal" for helping him recover.

On medical advice, he has not been doing official government work during his convalescence but has spoken to Queen Elizabeth and US President Donald Trump on the phone.

The British leader was diagnosed with the virus late last month but initially stayed at Downing Street and was filmed taking part in a round of applause for health workers in the days before he went to hospital.

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.