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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.

Washington, Apr 28: After nearly three weeks in an intensive care unit in Los Angeles, doctors treating 41-year-old Broadway actor Nick Cordero for COVID-19 were forced to amputate his right leg.

The flow of blood had been impeded by a blood clot: yet another dangerous complication of the disease that has been bubbling up in frontline reports from China, Europe and the United States.

To be sure, so-called "thrombotic events" occur for a variety of reasons among intensive care patients, but the rates among COVID-19 patients are far higher than would be otherwise expected.

"I have had 40-year-olds in my ICU who have clots in their fingers that look like they'll lose the finger, but there's no other reason to lose the finger than the virus," Shari Brosnahan, a critical care doctor at NYU Langone said.

One of these patients is suffering from a lack of blood flow to both feet and both hands, and she predicts an amputation may be necessary, or the blood vessels may get so damaged that an extremity could drop off by itself.

Blood clots aren't just dangerous for our limbs, but can make their way to the lungs, heart or brain, where they may cause lethal pulmonary embolisms, heart attacks, and strokes.

A recent paper from the Netherlands in the journal Thrombosis Research found that 31 percent of 184 patients suffered thrombotic complications, a figure that the researchers called "remarkably high" -- even if extreme consequences like amputation are rare.

Behnood Bikdeli, a doctor at New York-Presbyterian Hospital, assembled an international consortium of experts to study the issue. Their findings were published in the Journal of The American College of Cardiology.

The experts found the risks were so great that COVID-19 patients "may need to receive blood thinners, preventively, prophylactically," even before imaging tests are ordered, said Bikdeli.

What exactly is causing it? The reasons aren't fully understood, but he offered several possible explanations.

People with severe forms of COVID-19 often have underlying medical conditions like heart or lung disease -- which are themselves linked to higher rates of clotting.

Next, being in intensive care makes a person likelier to develop a clot because they are staying still for so long. That's why for example people are encouraged to stretch and move around on long haul flights.

It's also now clear the COVID-19 illness is associated with an abnormal immune reaction called "cytokine storm" -- and some research has indicated this too is linked to higher rates of clotting.

There could also be something about the virus itself that is causing coagulation, which has some precedent in other viral illnesses.

A paper in the journal The Lancet last week showed that the virus can infect the inner cell layer of organs and of blood vessels, called the endothelium. This, in theory, could interfere with the clotting process.

According to Brosnahan, while thinners like Heparin are effective in some patients, they don't work for all patients because the clots are at times too small.

"There are too many microclots," she said. "We're not sure exactly where they are."

Autopsies have in fact shown some people's lungs filled with hundreds of microclots.

The arrival of a new mystery however helps solve a slightly older one.

Cecilia Mirant-Borde, an intensive care doctor at a military veterans hospital in Manhattan, told AFP that lungs filled with microclots helped explain why ventilators work poorly for patients with low blood oxygen.

Earlier in the pandemic doctors were treating these patients according to protocols developed for acute respiratory distress syndrome, sometimes known as "wet lung."

But in some cases, "it's not because the lungs are occupied with water" -- rather, it's that the microclotting is blocking circulation and blood is leaving the lungs with less oxygen than it should.

It has just been a little under five months since the virus emerged in Wuhan, China, and researchers are learning more about its impact every day.

"While we react surprised, we shouldn't be as surprised as we were. Viruses tend to do weird things," said Brosnahan.

While the dizzying array of complications may seem daunting, "it's possible there'll be one or a couple of unifying mechanisms that describe how this damage happens," she said.

"It's possible it's all the same thing, and that there'll be the same solution."

Washington, Jul 15: The Trump administration has agreed to rescind its July 6 rule, which temporarily barred international students from staying in the United States unless they attend at least one in-person course, a federal district court judge said on Tuesday.

The U-turn by the Trump administration comes following a nationwide outrage against its July 6 order and a series of lawsuits filed by a large number of educational institutions, led by the prestigious Harvard University and Massachusetts Institute of Technology (MIT), seeking a permanent injunctive relief to bar the Department of Homeland Security (DHS) and the US Immigration and Customs Enforcement (ICE) from enforcing the federal guidelines barring international students attending colleges and universities offering only online courses from staying in the country.

As many as 17 US states and the District of Columbia, along with top American IT companies such as Google, Facebook and Microsoft, joined MIT and Harvard in the US District Court in Massachusetts against the DHS and the ICE in seeking an injunction to stop the entire rule from going into effect.

"I have been informed by the parties that they have come to a resolution. They will return to the status quo," Judge Allison Burroughs, the federal district judge in Boston, said in a surprise statement at the top of the hearing on the lawsuit.

The announcement comes as a big relief to international students, including those from India. In the 2018-2019 academic year, there were over 10 lakh international students in the US. According to a recent report of the Student and Exchange Visitor Program (SEVP), 1,94,556 Indian students were enrolled in various academic institutions in the US in January.

Judge Burroughs said the policy would apply nationwide.

"Both the policy directive and the frequently asked questions would not be enforced anyplace," she said, referring to the agreement between the US government and MIT and Harvard.

Congressman Brad Scneider said this is a great win for international students, colleges and common sense.

"The Administration needs to give us a plan to tackle our public health crisis - it can't be recklessly creating rules one day and rescinding them the next," he said in a tweet.

Last week, more than 136 Congressmen and 30 senators wrote to the Trump administration to rescind its order on international students.

"This is a major victory for the students, organisers and institutions of higher education in the #MA7 and all across the country that stood up and fought back against this racist and xenophobic rule," said Congresswoman Ayanna Pressley.

"Taking online classes shouldn't force international students out of our country," Congressman Mikie Sherrill said in a tweet.

In its July 6 notice, the ICE had said all student visa holders, whose university curricula were only offered online, "must depart the country or take other measures, such as transferring to a school with in-person instruction to remain in lawful status".

"If not, they may face immigration consequences, including but not limited to the initiation of removal proceedings," it had said.

In their lawsuit, the 17 states and the District of Columbia said for many international students, remote learning in the countries and communities they come from would impede their studies or be simply impossible.

The lawsuit alleged that the new rule imposes a significant economic harm by precluding thousands of international students from coming to and residing in the US and finding employment in fields such as science, technology, biotechnology, healthcare, business and finance, and education, and contributing to the overall economy.

In a separate filing, companies like Google, Facebook and Microsoft, along with the US Chamber of Commerce and other IT advocacy groups, asserted that the July 6 ICE directive will disrupt their recruiting plans, making it impossible to bring on board international students that businesses, including the amici, had planned to hire, and disturb the recruiting process on which the firms have relied on to identify and train their future employees.

The July 6 directive will make it impossible for a large number of international students to participate in the CPT and OPT programmes. The US will "nonsensically be sending...these graduates away to work for our global competitors and compete against us...instead of capitalising on the investment in their education here in the US", they said.