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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.

Feb 12: China on Wednesday reported another drop in the number of new cases of a viral infection and 97 more deaths, pushing the total dead past 1,100 as postal services worldwide said delivery was being affected by the cancellation of many flights to China.

The National Health Commission said 2,015 new cases had been reported over the last 24 hours, declining for a second day. The total number of cases in mainland China reached 44,653, although many experts say a large number of others infected have gone uncounted.

The additional deaths raised the mainland toll to 1,113. Two people have died elsewhere, one in Hong Kong and one in the Philippines.

In the port city of Tianjin, just southeast of Beijing, a cluster of cases has been traced to a department store in Baodi district. One-third of Tianjin’s 104 confirmed cases are in Baodi, the Xinhua state news agency reported.

A salesperson working in the store’s small home appliance section became the first individual in the cluster to be diagnosed on Jan. 31, Xinhua said. The store was already closed at that point, then disinfected on Feb. 1. Nevertheless, several more diagnoses soon followed.

The next to have their infections confirmed were also salespeople at the store. They had not visited Wuhan recently and, with the exception of one married couple, the patients worked in different sections of the store and did not know one another, according to Xinhua.

Japan’s Health Ministry said that 39 new cases have been confirmed on a cruise ship quarantined at Yokohama, bringing the total to 174 on the Diamond Princess.

The U.S. Postal Service said that it was “experiencing significant difficulties” in dispatching letters, parcels and express mail to China, including Hong Kong and Macau.

Both the U.S. and Singapore Post said in notes to their global counterparts that they are no longer accepting items destined for China, “until sufficient transport capacity becomes available.”

The Chinese mail service, China Post, said it was disinfecting postal offices, processing centers and vehicles to ensure the virus doesn’t spread via the mail and to protect staff.

It said the crisis is also impacting mail that transits China to other destinations including North Korea, Kazakhstan, Kyrgyzstan, Mongolia, Tajikistan, Turkmenistan, Uzbekistan and Vietnam.

The World Health Organization has named the disease caused by the virus as COVID-19, avoiding any animal or geographic designation to avoid stigmatization and to show the illness comes from a new coronavirus discovered in 2019.

The illness was first reported in December and connected to a food market in the central Chinese city of Wuhan, where the outbreak has largely been concentrated.

Zhong Nanshan, a leading Chinese epidemiologist, said that while the virus outbreak in China may peak this month, the situation at the center of the crisis remains more challenging.

“We still need more time of hard working in Wuhan,” he said, describing the isolation of infected patients there a priority.

“We have to stop more people from being infected,” he said. “The problem of human-to-human transmission has not yet been resolved.”

Without enough facilities to handle the number of cases, Wuhan has been building prefabricated hospitals and converting a gym and other large spaces to house patients and try to isolate them from others.

China’s official media reported Tuesday that the top health officials in Hubei province, of which Wuhan is the capital, have been relieved of their duties. No reasons were given, although the province’s initial response was deemed slow and ineffective. Speculation that higher-level officials could be sacked has simmered, but doing so could spark political infighting and be a tacit admission of responsibility.

The virus outbreak has become the latest political challenge for the party and its leader, Xi Jinping, who despite accruing more political power than any Chinese leader since Mao Zedong, has struggled to handle crises on multiple fronts. These include a sharply slowing domestic economy, the trade war with the U.S. and pushback on China’s increasingly aggressive foreign policies.

China is struggling to restart its economy after the annual Lunar New Year holiday was extended to try to curb the spread of the virus. About 60 million people are under virtual quarantine and many others are still working at home.

In Hong Kong, the diagnosis of four people living in an apartment building prompted worried comparisons with the deadly SARS pandemic of 17 years ago.

More than 100 people were evacuated from the building after a 62-year-old woman diagnosed with the virus was found living 10 floors directly below a man who was earlier confirmed with the virus.

Health officials called it a precautionary measure and sought to assuage fears of an epidemic, dismissing similarities to the SARS community outbreak at the Amoy Gardens housing estate in 2003.

Beijing, May 18: China has reported 25 new COVID-19 patients, the health authorities said on Monday, as 14 asymptomatic cases were detected in Wuhan, the first epicentre of the coronavirus where officials are doing mass testing of the city's entire 11 million population, taking the number of such cases in the city to 337, the highest in the country.

The death toll in China remained at 4,634 on Sunday with no new fatalities reported.

China's National Health Commission (NHC) reported seven new confirmed cases of COVID-19 and 18 asymptomatic cases on Sunday.

Jilin province where the government has implemented strict control measures in the last few days following reports of clusters of cases in Jilin city reported two cases on Sunday, while Shanghai city has reported one.

As of Sunday, the overall confirmed cases in China had reached 82,954, including 82 patients who are still being treated, and 78,238 people who have been discharged after recovery.

Also on Sunday, 18 new asymptomatic cases including two from abroad were reported in China, taking the total number under medical observation to 448, the NHC said.

Asymptomatic cases pose a problem as the patients are tested COVID-19 positive but develop no symptoms such as fever, cough or sore throat. However, they pose a risk of spreading the disease to others.

Wuhan which is undergoing mass testing of the city's entire over 11 million population to determine the prevalence of the virus has reported no new confirmed cases, but 14 new asymptomatic infections, taking the number of such cases in the city to 337, the highest in the country, according to the figures released by the local health commission on Sunday.

The death toll in Hubei province stood at 4,512, including 3,869 in Wuhan.

The province so far has reported 68,134 confirmed COVID-19 cases in total, including 50,339 in Wuhan, according to the officials figures.

As the cases dropped, China on Sunday exempted people in Beijing from wearing masks, signalling that the virus is under control in the national capital.

As the virus is abating in the country, China is opening up all its business including entertainment centres like Shanghai Disneyl and to show that it has managed to control the dreaded virus while the world is struggling with it with lockdowns and massive casualties.

The novel coronavirus which originated in Wuhan in December last year has claimed 315,185 lives and infected over 4.7 million people globally, according to Johns Hopkins University data.