Pakistan records 3,892 new coronavirus cases, tally reaches 188,926

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.

The total number of global coronavirus cases has topped 15.4 million, while the deaths have increased to over 631,000, according to the Johns Hopkins University.

As of Friday morning, the total number of cases stood at 15,439,456, while the fatalities rose to 631,926, the University's Center for Systems Science and Engineering (CSSE) revealed in its latest update.

The US accounted for the world's highest number of infections and fatalities at 4,034,831 and 144,242, respectively, according to the CSSE.

Brazil came in the second place with 2,287,475 infections and 84,082 deaths.

In terms of cases, India ranks third (1,238,798), and is followed by Russia (793,720), South Africa (408,052), Peru (371,096), Mexico (370,712), Chile (334,683), the UK (298,721), Iran (284,034), Spain (270,166), Pakistan (269,191), Saudi Arabia (260,394), Italy (245,338), Turkey (223,315), Colombia (218,428), France (216,667), Bangladesh (216,110), Germany (204,881), Argentina (148,027), Canada (114,398), Qatar (108,244) and Iraq (102,226), the CSSE figures showed.

The other countries with over 10,000 deaths are the UK (45,639), Mexico (41,908), Italy (35,092), France (30,185), India (29,861), Spain (28,429), Iran (15,074), Peru (17,654) and Russia (12,873).

Vienna, Apr 13: Top oil-producing countries agreed on "historic" output cuts to prop up prices hammered by the coronavirus crisis and a Russia-Saudi price war, sending crude prices soaring on Monday.

The US benchmark WTI climbed 7.7 percent to $24.52 a barrel in early Asian trade while Brent was up 5.0 percent at $33.08.

OPEC producers dominated by Saudi Arabia and allies led by Russia thrashed out a compromise deal via videoconference Sunday after Mexico had balked at an earlier agreement struck on Friday.

In the compromise reached Sunday they agreed to a cut of 9.7 million barrels per day from May, according to Mexican Energy Minister Rocio Nahle, down slightly from 10 million barrels a day envisioned earlier.

OPEC Secretary General Mohammad Barkindo called the cuts "historic".

"They are largest in volume and the longest in duration, as they are planned to last for two years," he said.

The agreement between the Vienna-based Organization of the Petroleum Exporting Countries and partners foresees deep output cuts in May and June followed by a gradual reduction in cuts until April 2022.

Barkindo added that the deal "paved the way for a global alliance with the participation of the G20".

Saudi Energy Minister Prince Abdulaziz bin Salman, who chaired the meeting together with his Russian and Algerian counterparts, also confirmed that the discussions "ended with consensus".