Large droplets are the main drivers of Covid transmission, masks can stop them: study, world news

Face masks can reduce the risk of spreading large COVID-19 droplets while speaking or coughing by up to 99.9 percent, according to a new study published in the journal Royal Society Open Science.

The study was part of a laboratory experiment with mechanical mannequins and human volunteers.

A woman standing two meters from a cough man without a mask will be exposed to 10,000 times more such droplets than if he were wearing one, even if he was only 50 centimeters away, they reported in the Royal Society Open Science magazine.

“There is no longer any doubt that face masks can dramatically reduce the spread of potentially virus-laden droplets,” senior author Ignazio Maria Viola, an expert in applied fluid dynamics at the Edinburgh University School of Engineering, told AFP.

Large respiratory droplets that act like projectiles before being pulled to the ground by gravity are considered the main drivers of SARS-CoV-2 transmission.

Smaller, sometimes called aerosol droplets, can float in the air for a long time.

“We continuously exhale a whole series of droplets, from microscale to millimeter,” said Maria Viola over the phone.

“Some of the droplets fall off faster than others,” he said, depending on temperature, humidity, and especially airspeed.

The study focused on particles larger than 170 microns in diameter – roughly two to four times the width of a human hair.

Aerosol particles that tend to follow currents in the air are generally described as being smaller than 20 or 30 microns.

Medium-sized droplets can behave in either case, the study found.

Universal wearing of masks

“When you wear a mask, you reduce virus transmission by an order of magnitude – ten times less,” said Maria Viola.

“In our study, we speak for the larger droplets we measure 99.9 percent fewer.”

According to the Institute for Health Metrics and Assessment (IHME) in Seattle, Washington, if a universal mask use policy were passed, 55,000 lives could be saved in the US in the next four months.

The institute’s model builders, who accurately predicted in mid-July that Covid-19 deaths in the United States would exceed 224,000 by November 1, forecast 561,000 deaths by April 1, 2021 according to current trends.

Wearing masks universally would reduce the global death toll by 400,000 from 2.9 million to 2.5 million over the same period. To date, the virus has claimed around 1.7 million lives.

Earlier this month, the World Health Organization (WHO) updated its Covid-19 guidelines on masks to recommend that they be worn around other people if there is insufficient ventilation.

The guidelines apply particularly in areas of known or suspected community transmission.

The primary purpose of masks is to reduce the emissions of virus-laden droplets from people who cough, sneeze, sing, speak, or just breathe. However, they can also help prevent droplets from being inhaled by the person wearing them.

“Cloth masks not only effectively block most large droplets – 20 to 30 microns and larger – but they can also block the exhalation of fine droplets and particles, often referred to as aerosols,” according to the CDC.

(With inputs from AFP)