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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.

Geneva, Jun 22: The global count of coronavirus cases has surpassed 8.7 million, with 183,020 new cases recorded on Sunday, the World Health Organisation said in its daily situation report.

Over the last 24 hours, 4,743 people died from COVID-19 worldwide, taking the death toll to 461,715 fatalities, according to the report.

The cumulative global toll of confirmed cases has now reached 8,708,008, as stated in the report.

The WHO Regional Director for Europe, Dr Hans Henri P. Kluge, shared that Europe accounts for 31 per cent of COVID-19 cases and 43 per cent of COVID-19 deaths globally.

Dr Kluge highlighted that several countries continue to face increasing disease incidence and that "preparing for the autumn is a priority now at the WHO Regional Office for Europe"

The United States continues to be worst affected by the contagion with the highest count of cases and fatalities -- 2.2 million and 118,895, respectively.

The novel coronavirus was declared a pandemic by WHO on March 11.

Munich, Feb 16: Iran's foreign minister said Saturday that US President Donald Trump is receiving bad advice if he believes an American "maximum pressure" campaign against his country will cause the government in Tehran to collapse.

Foreign Minister Mohammad Javad Zarif told a group of top defense officials and diplomats at the Munich Security Conference that the information provided to the president has dissuaded Trump from accepting offers from other leaders to mediate between Washington and Tehran.

"President Trump has been convinced that we are about to collapse so he doesn't want to talk to a collapsing regime," Zarif said.

To support his argument, the Iranian minister cited Trump's decision to pull out unilaterally in 2018 from Iran's nuclear deal with the US and other world powers. Trump said the landmark 2015 accord didn't address Iran's ballistic missile program or regional activities and needed to be renegotiated.

Since then, the Trump administration's re-imposition of US sanctions in a campaign of so-called "maximum pressure" have taken a severe toll on the Iranian economy and sent Iran's currency plunging.

"I believe President Trump, unfortunately, does not have good advisers," Zarif said. "He's been wanting for Iran to collapse since he withdrew from the nuclear deal." Zarif also said the killing of Iranian Gen. Qassem Soleimani in a US drone strike in Iraq on January 3 was a miscalculation by Washington that has galvanized support for Iran instead of increasing pressure on the regime.

The Iran nuclear deal, known as the Joint Comprehensive Plan of Action or JCPOA, promised Iran economic incentives in exchange for curbs on its nuclear program. It was intended to prevent Tehran from developing a nuclear bomb, which Iran insists it does not want to do.

Since the US withdrawal, the deal's other signatories - Germany, France, Britain, Russia and China - have unsuccessfully struggled to come up with ways to offset the effects of the new American sanctions.

Washington has pressured the other countries - so far without success - to abandon the deal entirely US Secretary of State Mike Pompeo said at the Munich Security Conference earlier Saturday that while there may be disagreements on what to do with the JCPOA, "when I talk to my counterparts here in Europe, everybody gets it."

"Everyone understands that these are folks who continue to build out their nuclear program," Pompeo said. "So there's a common understanding about the threat; we have tactical differences on how to proceed."

In recent months, Iran has steadily violated the limitations the deal placed on the amount of enriched uranium and heavy water it can stockpile, the number and type of centrifuges it can operate, and the purity of the uranium it enriches.

Iranian officials insist the moves are intended only to put pressure on the countries that remain part of the deal to provide economic help to Iran and that all the measures taken are fully reversible.

Zarif rejected Trump's suggestion of negotiating a new deal, saying the one negotiated during the Obama administration was the only vehicle for talks on Iran's nuclear program.

"There is no point in talking over something you already talked about. You don't buy a horse twice," he said.

"It's not about opening talks with the United States. It's about bringing the United States to the negotiating table that's already there," Zarif said.