Why should we wear a mask?

Beijing time on May 27, according tomedia reports, masks can be said to be one of the signs of infectious diseases, is lurking around us, invisible virus esled metaphors. Some will wrap their faces around their faces with scarves, some will pull up T-shirts and cover their mouths, and some lucky people will wear conspicuous medical masks and even N95 masks rarely seen abroad.

Why should we wear a mask?

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Just a few months ago, people in many countries did not wear a mask habit, if you wear a mask in a public place, will certainly attract a lot of amazing eyes. Now, wearing a mask has become a symbol of this special period. More and more people are choosing to wear masks in public places as governments begin to ease the blockade and allow people to go out.

But there is still much debate about whether ordinary people should be encouraged to wear masks.

Early in the outbreak, many governments warned people not to wear masks, or front-line medical personnel may lack the supply of masks, but also create a false sense of security. But some countries, such as the United States, have since changed their tune. Utah has said it will issue a free mask to all citizens who apply. Countries such as the Czech Republic, Slovakia, Austria, Morocco, Turkey and Germany have made it mandatory to wear a mask in public. As countries begin to deregulate, more and more may follow suit.

But can masks really affect the course of the war in this battle against the Covid-19?

“It’s critical that people wear masks in public places in countries that have flattened the epidemic curve. Chris Kenyon, director of the sexually transmitted diseases division at the Institute of Tropical Medicine in Antwerp, Belgium, said. He analyzed whether masks played a key role in limiting the spread of Covid-19 in some countries. “Most of them are Asian countries. Somehow, European experts (except the Czech Republic) have only recently begun to learn from the success of Asia. “

To understand how masks work, you must first understand how the new coronavirus is transmitted.

When the new coronavirus (Sars-CoV-2) infects someone, it invades human cells and begins to replicate itself. During replication, new viral particles pour out of cells and are suspended in the body fluids of the lungs, mouth and nasal cavity. Once an infected person coughs, tiny droplets,called aerosols, filled with viruses, are sprayed into the air.

A cough can produce up to 3000 droplets. There are also concerns that simply speaking can spread the virus. A recent study showed that the words “stay healthy” simply sprayed thousands of droplets invisible to the naked eye into the air.

Once left in the mouth, many larger droplets quickly settle onto the surface of nearby objects, and smaller droplets continue to hover in the air for hours until they are inhaled. Although it is not clear how viral droplets perform in air-conditioned indoor and outdoor environments, it is generally believed that viral droplets settle faster in the disturbed air. There are also reports that the new coronavirus can be transmitted through the ventilation system of buildings.

One study found that the Sars-CoV-2 virus can survive at least three hours in aerosol droplets, but a more recent study has not yet published that the Sars-CoV-2 virus is still contagious after being suspended in aerosol droplets for more than 16 hours, and that the new coronavirus is “particularly tenacious in aerosol form” compared to other similar coronaviruses previously studied.

Taken together, the new coronavirus remains contagious under the right conditions and stays in the air for several hours. And in indoor environments, the virus seems particularly easily transmitted through the air.

An unpublished analysis of 318 new crown cases found that Covid-19 was mostly transmitted in indoor environments, with particularly the number of cases transmitted at home, but also widespread in public transport, restaurants, cinemas and shops. The researchers found only one case that appeared to be transmitted outdoors.

The genetic material of the new coronavirus was also detected in the toilets and air in the rooms used by the patients. A study of a cluster infection at a restaurant in Guangzhou found that in poorly ventilated spaces, the virus can be transmitted to people sitting nearby in the form of aerosol droplets.

A recent study looked at the effectiveness of masks in preventing patients from spreading the virus. A standard medical surgical mask is enough to significantly reduce the number of viruses released by people with respiratory viruses through breathing and coughing, including a milder coronavirus, influenza virus and a rhinovirus that causes the common cold.

A proposal to lift closures states that large-scale nucleic acid testing should be carried out prior to the outbreak of community infections, while contacts should be tracked and isolated. If you’re identified as infected, the health department can track your family, social contacts, and professional contacts, but it’s hard to track your people on a bus or train. It would be helpful if the spread of such sites could be limited.

The importance of large-scale masks in the public is also linked to the large number of asymptomatic carriers in Covid-19. These people can also spread the virus to others. It is estimated that between 6 and nearly 18 per cent of new coronavirus infections do not show any symptoms. In addition, the incubation period for Covid-19 is approximately 5 days, but in some cases it can be up to 14 days. They may have infected many people before they develop symptoms and begin to develop the disease.

As a result, it is difficult to curb community transmission of Covid-19, but if everyone wears a mask, both infected and asymptomatic carriers wear masks, this helps reduce the number of viruses that spread to the environment and can infect others.

A study by the National Institutes of Health found that even wearing a homemade mask can reduce the droplets that come out when you speak.

Since masks can prevent infected people from spreading the virus to others, can they protect the uninfected and prevent people from inhaling the virus?

Professional masks such as N95 and European FFP-2 are certainly strong in filtering particulate matter. When the wearer breathes, 95% and 94% of particles with a diameter of 0.3 microns or more can be filtered out, respectively.

However, the masks’ ability to block the virus from entering is uneven. Some virus particles have a diameter of only 0.01 microns, and the researchers note that the new coronavirus is between 0.07 and 0.09 in diameter. However, respiratory viruses usually exist in the form of aerosol droplets, ranging in diameter from 0.1 to 900 microns, and blocking these droplets is often more critical.

Previous studies have suggested that smaller viruses can leak from N95 masks. But the study found that N95 masks were effective in blocking the flu virus.

Other studies have suggested that such masks can be effective in protecting people from new coronaviruses. An analysis of Chinese medical staff showed that staff wearing N95 masks would not be infected with the virus even if they cared for highly contagious patients. This is one of the reasons why such masks are so important to front-line medical workers.

The problem is that the supply of these masks abroad is already in short supply, and if ordinary people snap them up, front-line workers will be unprotected and exposed to the virus. WHO has urged the general public not to wear N95 masks to ensure adequate supply of masks for health workers. This is one of the considerations that many governments are reluctant to encourage people to wear masks.

While there is evidence that these masks can be reused after disinfection, this is not an ideal solution.

There is another problem with requiring people to wear masks: training on how to use them. If not worn properly, viral particles can still “take advantage” of the void around the mouth and nose. Facial hair can also affect the sealing of the mask, which in turn affects the effect. The U.S. Centers for Disease Control and Prevention has released a handbook for people who need to be a whisker. Some shaped beards can wear masks properly, while others may require shaving.

But beyond that, there are some simpler alternatives. A recent peer-reviewed study found that 3M medical surgical masks, the kind doctors wear during surgery, block particles larger than 0.02 microns in diameter by nearly 75 percent. Although not comparable to the N95 mask, it can also reduce the amount of particulate matter inhaled by the wearer. But if you cut a hole at the end of the stocking and put it on the mask, it’s possible to increase the particulate blocking rate to 90 percent.

Unlike N95 masks, medical surgical masks are not designed to fit the face tightly. This allows part of the air to enter the airways directly through the gap around the mask. The study found that adding a layer of nylon material to the outside of the mask could help reduce this.

But with medical surgical masks in short supply, many ordinary people have to find ways to make their own masks. There have been a wide number of mask tutorials on the Internet, most of which are made of cotton into pockets and then put into some sort of filter material. Some offered to vacuum dust bags, others sewed several coffee filter sheets between two handkerchiefs, or stacked pillowcases.

Yang Wang, an environmental engineer at the University of Missouri Technology, worked with a student on several masks and found that the higher the amount of cloth used, the better. The worst effect was the handkerchief, followed by a wool scarf, but 600 pillowcases were folded four times to keep 60% of the particles out. Masks made from air-conditioning anti-allergy filters and vacuum cleaner dust bags work best and are almost comparable to N95 masks.

The researchers also found that while pulling a T-shirt up to cover the nose could only block less than half of the aerosol, if you cover a two-layer or even three-layer T-shirt, it can help in an emergency. Materials such as silk and chemical fiber are also very effective. Flannel, wool felt and cotton tires can all be used to block ultrafine particles. Another study suggests that in an emergency, a sock can also be used to prevent it by flattening it and covering it tightly.

Like n95 and medical surgical masks, homemade masks can only work best for the first time. If you want to use it a few more times, you need to disinfect. The U.S. Centers for Disease Control and Prevention recommends regular cleaning of homemade masks. Hot water alone may not be enough, as a recent study found that the new coronavirus can withstand temperatures of at least 60 degrees Celsius. Fortunately, with soap and household disinfectants can easily destroy the oily envelope of the new coronavirus.

But none of the above materialcans can replace the N95 mask. This issue is very important for health officials who interpret the data we collect. What kind of particulate filtration level is safe enough? Sometimes we can only pick a general in a series of imperfect options, which is unfortunate, but it is.

But even without a mask that works perfectly, wearing a mask in a public place can still affect the trend of the outbreak and help reduce infection rates after the blockade is relaxed. As researchers at University College London have warned, the sidewalks in London and many cities around the world are not wide enough to keep a safe distance from others. In closed spaces such as public transport, it is even more difficult to keep your distance.

If enough people wear masks in public places, it can greatly affect the speed at which the new coronavirus can resume transmission among people. This is better if social isolation and hand washing are supplemented. An unpublished study by Alyssa State University found that 80 percent of people wearing masks, even if they are just effective, could reduce new York’s deaths by 17 to 45 percent in two months. Even if the mask is only 20 percent effective, it could reduce washington’s death toll by 24 to 65 percent and New York by 2 to 9 percent, if enough people wear it.

Researchers also suggest that giving priority to the provision of masks to older persons is also an effective measure in countries where masks are in short supply.

Although wearing a mask may be a little uncomfortable, it is difficult to see the other person’s facial expressions when talking, but for the safety and health of those around them, these are only a small price.