Can wearing masks really reduce Covid-19 transmission?


A mask is a symbol of the age of the epidemic – a visual metaphor representing a tiny, invisible enemy that may be lurking in any corner. Some people use a scarf wrapped around their face, while others transform themselves with a T-shirt pulled up to cover their mouths.

More creative masks have a lot of colorful, self-made things around their ears, while a lucky few wear a typical surgical mask or, more rarely, a N95 mask.

Mask controversy

While a few months ago, anyone wearing a mask in public might attract gazes in countries unfamiliar with this, now masks are a reminder. about the strange period we live in.

And as governments around the world began to relax the blockade to allow people to reintegrate into society, more and more people wear masks when they go out.

But there is still debate about whether to encourage the public to wear masks.

In the early days of the pandemic, many governments warned the public not to wear masks because fear of skyrocketing demand would make frontline health workers short of essential equipment and that could put people in sleep. artificial safety feeling.

Some countries – such as the United States – have taken a stance. The state of Utah says it will provide a free mask to any citizen who requests it.

And other countries like the Czech Republic, Slovakia, Austria, Morocco, Turkey and Germany are forced to wear masks in public places.

It is likely that other countries will follow these countries when they relax restrictions.

But did masks really make a difference in the battle against Covid-19?

One key point is that countries that pull straight to infectious lines are forced to wear masks in public places, “said Chris Kenyon, head of the sexually transmitted disease department at the Institute of Tropical Medicine in Antwerp, which has studied Researching whether a mask has a role in curbing the spread of Covid-19 in some countries, said.

Survive in the air

To understand why masks are effective, it is important to consider how the Covid-19 disease virus spreads from the root.

Once the virus enters someone, the Sars-CoV-2 virus that causes Covid-19 disease takes over the control of cells to multiply.

As they multiply, these new viruses then burst out of the cell and are suspended in body fluids in the lungs, mouth and nose.

When an infected person coughs out, he or she can shoot down a shower of tiny droplets – known as aerosols – filled with the virus into the air. A single cough can produce up to 3,000 splashes.

There are virus fears that can also spread just by talking. A recent study found that we discharge into the air thousands of drops of fire that the naked eye is not visible just by uttering the sentences: ‘ Stay healthy ‘ (keep healthy).

Once flying out of our mouth, many large drops will quickly fall to nearby surfaces while smaller droplets remain in the air for hours and someone will inhale.

Although how the virus-filled droplets work in air-conditioned rooms as well as outdoors is still not well understood, they are expected to fall to surfaces faster in air-conditioned environments. disturbance.

There are also several reports that corona virus can spread through ventilation in buildings.

According to a study by virologist Neeltje van Doremalen and her colleagues at the US National Institute of Allergy and Infectious Diseases in Hamilton, Montana, the Sars-CoV-2 virus was found to survive in droplets. this gas for at least three hours.

But a more recent and unpublished study has found that the Sars-CoV-2 virus remains infectious for more than 16 hours suspended in aerosol droplets.

This study found that the virus ‘had an incredible amount of toughness in aerosol form’ compared to other similar corona viruses they had studied.

Researchers together think that under the right conditions, viruses can linger in the air for hours and still infect humans if inhaled. And in indoor environments, they seem to be particularly contagious through the air.

An unpublished analysis of 318 Covid-19 outbreaks in China showed that it spread most often in indoor environments, especially in people’s homes, and on public transport, in restaurants, movie theaters and shops.

They found only one case of the virus that seemed to have spread when people were out in the street.

The genetic material of Sars-CoV-2 has also been detected in the air in toilets and rooms used by Covid-19 infected people.

A study of a cluster of cases in a restaurant in Guangzhou, China, showed that in poorly ventilated spaces, the virus can spread to people sitting close to each other through aerosolized droplets.

Asymptomatic cases

“Respirators can reduce the spread of infection in the community, especially in public transportation systems and crowded areas,” said Ben Cowling, head of epidemiology and statistical statistics at University of Hong Kong, said.

He and his colleagues recently published a study on the effectiveness of masks in preventing the spread of viruses from infected people.

They found that standard surgical masks were sufficient to significantly reduce the amount of virus released from the breaths and coughs of people infected with various respiratory viruses, including a mild coronavirus, the flu. and the common cold germs.

“One of the proposals to lift the blockade is to apply large-scale testing along with contact tracing and isolation, to overcome infection in the community,” Cowling said.

“If you are determined to be infected with a virus, health authorities can track your relatives, social contacts and professional relationships, but it is difficult to find out who you are sitting next to on the bus. or the train. “

Asymptomatic casesAsymptomatic cases

“If we could limit the spread of infection in these places, it would be really helpful.”

One of the reasons that wearing public masks is so important in combating the Covid-19 epidemic is the widespread presence of asymptomatic infected people who can still pass the virus to others.

It is estimated that between 6% and nearly 18% of people infected with the virus can carry the virus without symptoms.

In addition, the incubation period is about five days, but in some cases up to 14 days, before symptoms appear. Even people with signs of infection may have infected many people before they started falling ill.

“This makes stopping infection in the community especially difficult,” Cowling said.

“But if everyone is wearing a mask, that is, people who are infected and have no symptoms also wear a mask, that could help reduce the amount of virus that enters the environment and is potentially contagious.

Even wearing a homemade mask can reduce the amount of droplets each of us emits when talking, according to a study by scientists at the US National Institutes of Health in Bethesda, Maryland.

Is it possible to prevent viruses from invading?

So, if masks can help prevent people who have the virus from spreading to others, will it also help keep uninfected people from breathing in the virus?

Certainly the ability to filter particles in the air of a dedicated, disposable mask such as the N95 respirator and the equivalent FFP-2 respirator in Europe is very high.

They are designed to passively filter airborne particles of 95% and 94% respectively – to particles as small as 0.3 micrometers – when the wearer breathes.

However, the performance of these masks in preventing the virus from entering the body is unclear.

Some viruses can be as small as 0.01 micrometres, while researchers have reported that the corona virus that causes Covid-19 has a size of 0.07-0.09 micrometers.

However, respiratory viruses tend to float in aerosol droplets, which can range in size from 0.1 to 900 micrometers, so blocking these viruses is often more important.

Some previous studies have suggested that smaller germs than we thought could pass through the N95 respirator’s filter, but they have been shown to be effective at stopping influenza viruses.

There are several studies showing that these masks are effective in protecting people from Covid-19.

An analysis of health workers in China showed that people wearing N95 masks are not infected with the virus, even though they care for extremely infectious patients. This is one of the reasons why these masks are considered so important for frontline health workers.

The concern is that, if the public buys all the resources that are already in shortage, it will expose essential health workers, who are most likely to be exposed, unprotected and vulnerable. love.

Worn properly

Although there is currently some evidence that a gas mask can be disinfected for reuse, it is not the perfect solution.

“We really need to make sure there’s enough supplies of masks for health workers,” Cowling added.

It is the dearth of Personal Protective Equipment (PPE) such as the N95 mask that has led some scientists to seek to develop alternatives from materials that can be found in hospitals.

Another problem with asking the public to wear a mask is the need to give instructions on how to wear it properly.

If the mask is not worn properly, the closed area around the mouth and nose can still let the virus slip into the side.

A mustache can also affect the effectiveness of a mask because it keeps the mask from closing.

The Centers for Disease Control and Prevention (CDC) has published helpful guidelines for anyone with a beard who wants to wear a mask.

Worn properlyWorn properly

Getty Images PICTURE SOURCE, GETTY IMAGES
But there are also simpler alternatives. A recent study, but not peer-reviewed, has found that 3M surgical masks – the type of surgeon worn in the operating room – can remove nearly 75% of particles up to 0.02 in size. micrometer.

Although less effective than the N95 respirator, surgical masks can still help reduce the number of inhaled particles.

But by cutting a hole in the heel of the sock and wearing it on a mask can improve the ability of the mask and filter up to 90% of particles.

“The surgical mask, unlike the N95 respirator, is designed to fit loose on the face,” said Loretta Fernandez, an environmental chemist at Northeastern University, Boston, Massachusetts, one of who participated in this study, said.

“This allows the air to find its way around the respirator to reach the breathing area rather than straight through the mask.” They found that adding extra nylon on the outside of the mask reduced this.

Fernandez and collaborator Amy Mueller, an engineer at Northeastern University, also looked at the effectiveness of various homemade masks.

The most effective type uses multiple layers of fabric, although it is still not as effective as N95 masks and surgical masks.

However, adding a layer of nylon on top to allow masks to adhere to the face increases the efficiency to the point where some homemade masks can prevent 80% of the particles.

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