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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, Feb 18: A hospital director at the epicentre of China's virus epidemic died on Tuesday, state media said, the latest medical worker to fall victim to the new coronavirus spreading across the country.

The COVID-19 virus, which is believed to have originated in Wuhan late last year, has infected more than 72,000 people and killed nearly 1,900.

Liu Zhiming, the director of Wuchang Hospital in Wuhan, died Tuesday morning after "all-out rescue efforts failed," state broadcaster CCTV reported.

China said last week that six medical workers had died from the virus, while 1,716 have been infected.

Liu's death was initially reported by Chinese media and bloggers shortly after midnight on Tuesday -- but the stories were later deleted and replaced with reports that doctors were still trying to save him.

After initial reports of his death were denied, the hospital told AFP on Tuesday morning that doctors were giving him life-saving treatment.

Liu's death has echoes of that of Wuhan ophthalmologist Li Wenliang, who had been punished by authorities for sounding the alarm about the virus in late December.

Li's death prompted a national outpouring of grief as well as anger against the authorities, who were accused of mishandling the crisis.

People took to social media to mourn Liu on Tuesday, with many users on the Twitter-like Weibo platform drawing critical comparisons between Liu's death and Li's.

In both cases their deaths were initially reported in state media posts -- later deleted -- and their deaths denied, before being finally confirmed again.

"Has everyone forgotten what happened to Li Wenliang? They forcefully attempted resuscitation after he died," one Weibo commenter wrote.

Another commenter said, Liu "already died last night, (but) some people are addicted to torturing corpses".

A hashtag about Liu's death had 29 million views by Tuesday afternoon.

Doctors in Wuhan face shortages of masks and protective bodysuits, with some even wearing makeshift hazmat suits and continuing to work despite showing respiratory symptoms, health workers have told AFP.

Hubei province and its capital Wuhan have been the hardest hit by the virus, accounting for nearly 1,800 of the deaths from the virus so far.

Moscow, Jul 13: Russia has become the first nation to complete clinical trials of a COVID-19 vaccine on humans. Chief researcher Elena Smolyarchuk, who heads the Center for Clinical Research on Medications at Sechenov University, told Russian news agency TASS on Sunday that the human trials for the vaccine have been completed at the university and the volunteers will be discharged soon.

"The research has been completed and it proved that the vaccine is safe. The volunteers will be discharged on July 15 and July 20," Smolyarchuk was quoted as saying in the report.

Though the results have been favourable with respect to the medication’s effectiveness, no further information was provided on when this vaccine would enter commercial production stage.

Russia had allowed clinical trials of two forms of a potential COVID-19 vaccine developed by the Gamaleya National Research Center for Epidemiology and Microbiology on June 18.

The first vaccine, in the form of a solution for intramuscular administration, was carried out at the Burdenko Military Hospital.

Another vaccine, in the form of a powder for the preparation of a solution for intramuscular administration, was carried out at Sechenov First Moscow State Medical University.

The first stage of research on the vaccine at Sechenov University involved a group of 18 volunteers and the second group involved 20 volunteers.

After vaccination, all volunteers were expected to remain in isolation in a hospital for 28 days.

Earlier, results of the COVID-19 vaccine tests performed on a group of volunteers in Russia showed that they were developing immunity to the coronavirus.

"The data obtained by the Gamalei National Research Center for Epidemiology and Microbiology, proves that volunteers of the first and second groups are forming an immune response after injections of the vaccine against the coronavirus," according to an earlier statement from the Russian Defense Ministry.

Russia has reported 719,449 cases and 11,188 deaths to date.

There are at least 21 vaccines currently under key trials, according to the World Health Organisation (WHO).

The overall number of global COVID-19 cases crossed 12.9 million, while the deaths have increased to more than 5,69,000, according to Johns Hopkins University in the US.

As of Monday morning, the total number of cases stood at 1,29,10,357, while the fatalities rose to 5,69,128.

The US accounted for the world's highest number of infections at over 33 lakh. Brazil came in the second place with over 18 lakh infections. India is third worst affected with over 8.7 lakh people reported to have COVID-19.