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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.

Beijing, Jan 21: The Chinese official investigating a pneumonia outbreak stemming from a new coronavirus said the disease can spread from person to person but can be halted with increased vigilance, as authorities on Tuesday confirmed a fourth death.

Zhong Nanshan said there was no danger of a repeat of the Severe Acute Respiratory Syndrome (SARS) epidemic that killed nearly 800 people globally during a 2002-2003 outbreak, which started in China, as long as precautions were taken.

"It took only two weeks to identify the novel coronavirus," state news agency Xinhua quoted Zhong as saying late on Monday.

The outbreak was still in its early stages and China had good surveillance and quarantine systems to help control it, he added.

The outbreak has spread from the central city of Wuhan to cities including Beijing and Shanghai, with more than 200 cases reported so far. Four cases have been reported outside China - in South Korea, Thailand and Japan.

Australia on Tuesday said it would screen passengers on flights from Wuhan amid rising concerns that the virus will spread globally as Chinese travellers take flights abroad for the Lunar New Year holiday starting this week.

Authorities around the globe, including in the United States and many Asian countries, have stepped up screening of travellers from Wuhan.

Chinese authorities confirmed a total of 217 cases of the virus in China as of 6 p.m. (1000 GMT) on Monday, state television reported, 198 of which were in Wuhan.

A fourth person died on Jan. 19, the Wuhan Municipal Health Commission said. The 89-year-old man, who had underlying health diseases including coronary heart disease, developed symptoms on Jan. 13 and was admitted to hospital five days later, it added.

Zhong, who is renowned in China for his work fighting SARS in 2003, confirmed that the virus can pass from person-to-person.

Fifteen medical workers in Wuhan had been diagnosed with pneumonia, with one other suspected case, the Wuhan Municipal Health Commission said. Of the infected staff, one was in critical condition.

In Shanghai, officials on Tuesday confirmed a second case involving a 35-year-man who had visited Wuhan in early January, and said they were monitoring four other suspected cases.

The virus causes a type of pneumonia and belongs to the same family of coronaviruses as SARS. Symptoms include fever and difficulty in breathing, which are similar to many other respiratory diseases and pose complications for screening efforts.

The World Health Organisation (WHO) said on Monday an animal source appeared most likely to be the primary origin of the outbreak and that some "limited human-to-human transmission" occurred between close contacts.

The Geneva-based U.N. agency convened an emergency committee for Wednesday to assess whether the outbreak constitutes an international health emergency and what measures should be taken to manage it.

So far, the WHO has not recommended trade or travel restrictions, but a panel of independent experts could do so or make other recommendations to limit spread.

Washington, Apr 11: China is considered a developing country, make the United States too a developing one, US President Donald Trump said on Friday, alleging that Beijing has taken advantage of his country.

"China has been unbelievably taken advantage of us and other countries. You know, for instance, they are considered a developing nation. I said well then make us a developing nation too,” Trump told reporters at his daily White House news conference on coronavirus.

The president was responding to a question on China.

“They get big advantages because they are a developing nation. India, a developing nation. The United States is a big developed nation. Well, we have plenty of development to do,” he said.

Reiterating that United States was taken advantage of by the World Trade Organization, Trump said the Chinese economy started booming after it joined WTO with the help of the US.

“If you look at the history of China, it was only since they went into the WTO that they became a rocket ship with their economy. They were flatlined for years and years,” he said.

“Frankly, for many, many decades. And it was only when they came into the WTO that they became a rocket ship because they took advantage of all -- I'm not even blaming them. I'm saying how stupid were the people that stood here and allowed it to happen,” he said.

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The Trump Administration will now allow that to happen, he said.

“If they don't treat us fairly, will leave. But now we're starting to win cases,” he said.

Alleging that China has taken advantage of the United States for 30 years, he said, China has taken advantage of the US through WTO and using rules that are unfair to the United States.

"They should have never been allowed it, this should have never been allowed to happen", he added.

“When China joined and was allowed to join under those circumstances the WTO, that was a very bad day for the United States because they have rules and regulations that were far different and far easier than our rules and regulations,” he said.

“Plus. They took advantage of them down to the last. China took advantage of them like few people would even think to take advantage of them and again they are considered right a developing nation,” he added.

The United States, he rued, is not considered a developing nation.

“The were given advantages (for being a developing nation). For many years China has ripped off the United States. Then I came along and right now, as you know, China is paying 25 percent," said Trump, adding that the US is now gaining "billions and billions and billions of dollars in tariffs from China”.

The US is not paying, he asserted.

“Not every country is China but China would devalue their currency and they would also pour out money and they essentially were paying most of those tariffs not us,” he said.