Blue Whale challenge: Class 7 boy jumps off school building

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, Feb 28: Saudi Arabia on Thursday (Feb 27) suspended visas for visits to Islam's holiest sites for the "umrah" pilgrimage, an unprecedented move triggered by coronavirus fears that raises questions over the annual hajj.

The kingdom, which hosts millions of pilgrims every year in the cities of Mecca and Medina, also suspended visas for tourists from countries with reported infections as fears of a pandemic deepen.

Saudi Arabia, which so far has reported no cases of the virus but has expressed alarm over its spread in neighbouring countries, said the suspensions were temporary. It provided no timeframe for when they will be lifted.

"The kingdom's government has decided to take the following precautions: suspending entry to the kingdom for the purpose of umrah and visit to the Prophet's mosque temporarily," the foreign ministry said in a statement.

"Suspending entry into the kingdom with tourist visas for those coming from countries, in which the spread of the new coronavirus (COVID-19) is a danger."

The move comes as Gulf countries implement a raft of measures, including flight suspensions and school closures, to curb the spread of the disease from people returning from pilgrimages to Iran.

Even as the number of fresh coronavirus cases declines at the epicentre of the disease in China, there has been a sudden increase across the Middle East.

Since its outbreak, the United Arab Emirates has reported 13 coronavirus cases, Kuwait has recorded 43, Bahrain has 33 and Oman is at four cases.

Iran has emerged as a major hotspot in the region, with 19 fatalities from 139 infections - the highest death toll outside China, where COVID-19 originated.

While no cases have been reported in Saudi Arabia, one citizen is reported to be infected in Kuwait along with four Saudi women in Bahrain - all of whom had returned from Iran.

'UNPRECEDENTED' MOVE

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

There was no clarity over how the move would affect the annual hajj pilgrimage due to start in late July.

Some 2.5 million faithful travelled to Saudi Arabia from across the world to take part in last year's hajj - one of the five pillars of Islam.

The event is a key rite of passage for Muslims and a massive logistical challenge for Saudi authorities, with colossal crowds cramming into relatively small holy sites.

"This move by Saudi Arabia is unprecedented," Ghanem Nuseibeh, founder of London-based risk consultancy Cornerstone Global Associates, told news agency.

"The concern for Saudi authorities would be Ramadan, which starts at the end of April, and hajj afterwards, should the coronavirus become a pandemic."

The holy fasting month of Ramadan is considered a favourable period by Muslim pilgrims to perform the umrah.

Saudi Arabia's custodianship of Mecca and Medina - Islam's two holiest sites - is seen as the kingdom's most powerful source of political legitimacy.

But a series of deadly disasters over the years has prompted criticism of the Sunni kingdom's management of the pilgrimage.

In September 2015, a stampede killed up to 2,300 worshippers - including hundreds of Iranians - in the worst disaster ever to strike the pilgrimage.

The pilgrimage forms a crucial source of revenue for the government, which hopes to welcome 30 million pilgrims annually to the kingdom by 2030.

De facto ruler Crown Prince Mohammed bin Salman's Vision 2030 reform plan seeks to shift the economy of Saudi Arabia - the world's top crude exporter - away from oil dependency towards other sources of revenue, including religious tourism.

May 9: Union Home Minister Amit Shah has said the West Bengal government is not allowing trains with migrant workers to reach the state that may further create hardship for the labourers.

In a letter to West Bengal Chief Minister Mamata Banerjee, Shah said not allowing trains to reach West Bengal is "injustice" to the migrant workers from the state.

Referring to the 'Shramik Special' trains being run by the central government to facilitate transport of migrant workers from different parts of the country to various destinations, the home minister said in the letter that the Centre has facilitated more than two lakh migrants workers to reach home.

Shah said migrant workers from West Bengal are also eager to reach home and the central government is also facilitating the train services.

"But we are not getting expected support from the West Bengal. The state government of West Bengal is not allowing the trains reaching to West Bengal. This is injustice with West Bengal migrant labourers. This will create further hardship for them," Shah wrote.