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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.

Riyadh, Mar 6: Saudi Arabia on Thursday emptied Islam's holiest site for sterilisation over fears of the new coronavirus, an unprecedented shutdown state media said will last while the year-round Umrah pilgrimage is suspended.

The kingdom halted the pilgrimage for its own citizens and residents on Wednesday, on top of restrictions announced last week on foreign pilgrims to stop the disease from spreading.

State television relayed images of an empty white-tiled area surrounding the Kaaba -- a large black cube structure inside Mecca's Grand Mosque -- which is usually packed with tens of thousands of pilgrims.

As a "precautionary measure", the area will remain closed as long as the umrah suspension lasts but prayers will be allowed inside the mosque, state-run Saudi Press Agency cited a mosque official as saying.

Additionally, the Grand Mosque and the Prophet's Mosque in the city of Medina will be closed an hour after the evening "Isha" prayer and will reopen an hour before the dawn "Fajr" prayer to allow cleaning and sterilisation, the official added.

A group of cleaners was seen scrubbing and mopping the tiles around the Kaaba, a structure draped in gold-embroidered gold cloth towards which Muslims around the world pray.

A Saudi official told news agency the decision to close the area was "unprecedented".

On Wednesday, Saudi Arabia suspended the umrah for its own citizens and residents over fears of the coronavirus spreading to Islam's holiest cities.

The move came after authorities last week suspended visas for the umrah and barred citizens from the six-nation Gulf Cooperation Council from entering Mecca and Medina.

Saudi Arabia on Thursday declared three new coronavirus cases, bringing the total number of reported infections to five.

The umrah, which refers to the Islamic pilgrimage to Mecca that can be undertaken at any time of year, attracts millions of Muslims from across the globe annually.

The decision to suspend the umrah mirrors a precautionary approach across the Gulf to cancel mass gatherings from concerts to sporting events.

It comes ahead of the holy fasting month of Ramadan starting in late April, which is a favoured period for pilgrimage.

It is unclear how the coronavirus will affect the hajj, due to start in late July.

Some 2.5 million faithful travelled to Saudi Arabia from across the world in 2019 to take part in the hajj, which is one of the five pillars of Islam as Muslim obligations are known.

The event is a massive logistical challenge for Saudi authorities, with colossal crowds cramming into relatively small holy sites, making attendees vulnerable to contagion.

Already reeling from slumping oil prices, the kingdom risks losing billions of dollars annually from religious tourism as it tightens access to the sites.

Brasilia, Jul 14: Brazil has reported new 20,286 coronavirus cases in last 24 hours taking the country's total to 1.8 million, Sputnik reported citing the health ministry.

The country's death toll has increased by 733 in the same period of time. The death toll from the infection has touched 72,833.

Over 1.1 million people have recovered from COVID-19 in Brazil since the start of the epidemic in the country, according to the health ministry.

Brazil has the second-highest coronavirus death toll, it is surpassed only by the United States.