Pakistan reports 3,938 new COVID-19 cases, death toll reaches 1,621

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.

Paris, Jul 20: Two coronavirus vaccine candidates have proven safe for humans and produced strong immune reactions among patients involved in separate clinical trials, doctors said on Monday.

The first trial among more than 1,000 adults in Britain found that the vaccine induced "strong antibody and T cell immune responses" against the novel coronavirus.

A separate trial in China involving more than 500 people showed most had developed widespread antibody immune response.

The studies, published in The Lancet medical journal, constitute a major step on the road towards a COVID-19 vaccine that is effective and safe for widespread use.

The authors of the studies said that they encountered few adverse side-effects from the vaccine candidates.

However, they cautioned that more research was needed, particularly among older adults, who are disproportionately at risk of dying of COVID-19.

Co-author Sarah Gilbert from the University of Oxford said the results "hold promise".

"If our vaccine is effective, it is a promising option as these types of vaccine can be manufactured at large scale."

London: Italy on Friday recorded the most daily deaths of any country since the start of the coronavirus pandemic and Spain had its deadliest day, as British Prime Minister Boris Johnson became the first major world leader to test positive.

Italy reported 969 new deaths, Spain 769 and France 299 as Europe reeled from a crisis that has put millions at risk around the world and threatened a global economic meltdown.

In other grim milestones, AFP tallies showed a total of 300,000 cases now recorded in Europe with more than 26,000 deaths worldwide, and the United States overtook China as the country with the most infections.

Italy showed infection rates continuing a downward trend and Spain said its rate of new infections appeared to be slowing, but other countries were bracing to feel the full impact of the virus's spread.

The World Health Organization's regional director for Africa warned the continent faced a "dramatic evolution" of the pandemic, as South Africa became the latest nation to start life under lockdown and reported its first COVID-19 deaths.

Johnson, whose country has seen more than 14,000 declared coronavirus cases and 759 deaths, said he had developed mild symptoms over the previous 24 hours and was self-isolating after testing positive.

Britain's Health Secretary Matt Hancock also tested positive with mild symptoms.

Europe has suffered the brunt of the coronavirus crisis in recent weeks, with millions across the continent on lockdown and the streets of Paris, Rome and Madrid eerily empty.

In France — where nearly 2,000 people have died -- the government announced it was extending its stay-at-home order until at least April 15. While severe, the 299 new deaths it recorded on Friday was lower than the 365 reported the previous day.

The death of a 16-year-old girl from the virus has particularly shaken France, and shattered the belief of many young people that they are immune.

The girl's mother Sabine told AFP that Julie "just had a cough" at first but deteriorated quickly. She died on Wednesday, less than a week after showing her first symptoms.

"It's unbearable," Sabine said. "We were supposed to have a normal life."

Focus was also turning to the United States, where the number of known infections jumped by 18,000 on Friday, reaching more than 97,000 -- higher than both China and Italy. The US also recorded 345 deaths over the past 24 hours, with a total toll of 1,478.

In New York City, health workers are battling a surging toll of dead and infected at the US epicentre of the crisis, including an increasing number of younger patients.

"Now it's 50-year-olds, 40-year-olds, 30-year-olds," said one respiratory therapist at the Jewish Medical Center in Queens.

They "didn't listen about not going out or protecting themselves and washing their hands", he said.

- 'Afraid and lost' -

The coronavirus first emerged in China late last year before spreading globally, with more than half a million declared cases in 183 countries and territories.

Over the last six days, as many new cases have been diagnosed around the world as in the previous 80 days.

Beijing managed to contain its spread with lockdowns and quarantines and its epicentre Wuhan is in the process of easing severe movement restrictions in place for two months.

Three billion people around the world have been told to stay indoors.

In a historic first, Pope Francis performed the rarely recited "Urbi et Orbi" blessing to an empty Saint Peter's Square.

"Thick darkness has gathered over our squares, our streets and our cities; it has taken over our lives, filling everything with a deafening silence and a distressing void, that stops everything as it passes by," he said.

"We find ourselves afraid and lost," he said, describing the coronavirus as a "tempest".

Health care systems even in the most developed nations are stretched to breaking point and medical workers have been having to make difficult choices.

"If I've got five patients and only one bed, I have to choose who gets it," Sara Chinchilla, a paediatrician at a hospital near Madrid, told AFP.

The WHO's chief Tedros Adhanom Ghebreyesus said the dire lack of protective gear for frontline health workers was one of the most pressing problems in the fight to prevent deaths.

"The chronic global shortage of personal protective equipment is now one of the most urgent threats to our collective ability to save lives," he told a virtual news conference in Geneva.

Lockdowns and other measures are wreaking havoc on the global economy, with fears of a downturn worse than the Great Depression of the 1930s.

"It is clear that we have entered a recession" that will be worse than in 2009 following the global financial crisis, International Monetary Fund chief Kristalina Georgieva said Friday.

Unprecedented stimulus measures have helped markets bounce back after a brutal month, but people around the world are bracing for economic hardship.

The United States reported that 3.3 million people applied for unemployment benefits last week -- by far the highest number ever recorded.

Retail workers in particular have suffered as many countries shutter non-essential business, while airlines and the global tourism industry have been dealt devastating blows.

The fashion industry was the latest hit on Friday, with Paris men's fashion week and haute couture shows cancelled along with Milan men's fashion week.

- Armies of volunteers -

The World Tourism Organization said Friday it expected tourist arrivals to fall by 20-30 percent this year, with losses of $300 billion-450 billion in international tourism receipts.

But there have been rays of hope in the midst of the crisis.

Armed groups in Cameroon, the Philippines and Yemen have moved in recent days to reduce violence after UN Secretary General Antonio Guterres issued an appeal for ceasefires.

And armies of volunteers have emerged in many countries to bring help to the needy, with food deliveries for the elderly, free taxi rides, accommodation for health workers, and even home-sewn face masks.