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How good are the masks to protect us from Covid?

Mannequin with face mask and face shield

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Mask, screen or better to use both?

With the relaxation of the containment rules and the opening of shops, bars and restaurants in many cities around the world, mouth masks have become a garment for everyday use.

In the UK and other European countries, for example, many clothing brands offer reusable fabric face masks in a variety of models, patterns and colors.

But in recent weeks, a new protective element has begun to appear on the streets: there is one clear face protection or protection of plastic, which until recently was only used by healthcare professionals or in medical or hospital settings.

At first glance, these protective shields look more comfortable than masks: they are not in direct contact with the nose and mouth, they are easier to breathe, speak, provide less heat and are definitely less claustrophobic.

But do they protect us as much as a face mask? Can we replace one with another?


According to a recently published opinion piece in JAMA, the journal of the American Medical Association, these screens have a number of benefits.

“They are comfortable to wear, protect access portals froml virus and they reduce the potential autoinoculation, because they avoid touching the user̵

7;s face, “says the text, prepared by Dr. Eli Perencevich, an infectious disease specialist at the University of Iowa and two other researchers.

Unlike masks, you do not need to remove them facilitate communication, They can be reused indefinitely if they are not damaged and easily cleaned with soap and water or common disinfectants, the article says.

Waiter with face shield

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For people who are in constant contact with the public and need to communicate orally, the screens are much more comfortable.

The authors do not advocate the use of this monitor as the only measure, but they believe it may be another element of a coronavirus containment strategy that includes hand washing, social distance and contact tracing.

On the other hand, they add, face shields cover a much wider area in the face, including eyes, which is another entry route for SARS-CoV-2.

Wider protection

According to a study on host simulation from 2014, a good plastic screen can reduce the total exposure to cough drops and aerosols (small drops) in a 96% at a distance of 46 cm.

However, with the smaller sprays, the shield was less effective, blocking 68% immediately after coughing and only 23% for the next 30 minutes, as these smaller sprays can float under the visor. , in the space where inhalation takes place.

According to Julian Tang, Professor of the Department of Respiratory Sciences at the University of Leicester, UK, face shields are generally quite effective, but acknowledges that it is difficult to compare them directly with surgical masks, and that the studies that have been done so far have only done so to a limited extent.

If we are to use them, the most important thing is to think about “how far the protector bends cover ears (if there is space, aerosols can enter that way and cause an infection) and how far it extends below (to protect us from the liquid aerosols we can inhale under protection), Tang tells BBC Mundo.

Another factor to keep in mind is that there is no gap at the top, where the visor rests on the forehead, to reduce the risk of exposure to droplets or aerosols that may fall from above.

Neither alone nor in society

However, not all experts agree that screens are a good option, although they accept that when the use of a mask is not feasible – either because it affects communication too much or for some reason – it is always better to use it than to go with it. the naked face.

Health worker with protective equipment

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Until relatively recently, face shields were used only in the hospital setting.

Aaron Glatt, head of the medical department at Mount Sinai South Nassau Hospital in the United States, believes that the benefits of the monitors vary depending on who uses them.

“We recommend that it be used for a healthcare professionalsFor example, you should enter the room of a patient who has or is suspected of having covid-19 and does not wear a mask, he tells BBC Mundo.

“In that case, the potential for the patient to expel virus particles is great and it is important to protect the healthcare professional’s eyes with glasses or face protection over the mask.”

“But in a societal context, we recommend the mask (and not the screen), as it is more effective in preventing the virus from spreading to surrounding areas. If the person wearing the mask shows a virus, the traps will be caught by the mask. “

In short, “it’s one most effective mechanismGladly adds.

The US Centers for Disease Control and Prevention (CDC) also does not recommend that they be used in everyday life or as a substitute for mouthwashes.

But if someone decides to wear it without a mask underneath, they should make sure that it covers the sides of the face and extends under the chin.

Protection against aerosols

Although face shields prevent the drops from passing, as their contour is not sealed on the face, they allow a certain number of sprays to pass.

Waitress with face shield

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With the relaxation of containment measures, the risk of transmission of covid-19 increases.

The World Health Organization (WHO) recently acknowledged, in response to an open letter published by more than 200 researchers, that there is growing evidence that the coronavirus can be spread by these small airborne particles.

“The airborne can not excludeI know in stages with crowds or in closed and poorly ventilated places, “a representative of the organization said on Wednesday.

However, this transmission path explains Luis Ostrosky, Professor of Infectious Diseases at the McGovern School of Medicine at UTHealth in Houston, USA to BBC World. it is not the most important.

“We think the primary route of transmission for covid-19 is through the drops, so there are two ways to protect yourself from them: one is by covering your mouth and nose with a mask, but it leaves the rest of your face exposed.”

“The other is with a face shield, which covers the entire face,” says Ostrosky.

“Aerosols can contribute to transmission in closed environments, especially in situations such as medical procedures, but this is a controversial issue.”

Social distance

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Maintaining social distance and washing hands are still two crucial steps to counter the pandemic.

“So there is a growing consensus among epidemiologists that the screen can be one very good option to protect themselves in a Community relationship. “

In Ostrosky’s opinion, they are particularly beneficial for young children because they reveal facial expressions.

“I think they will be an element the key to reopening schools“.

The WHO, for its part, points out that screens for the general public can be considered as an option in the event of a shortage of non-medical masks, but says that they are “lower than the masks in terms of preventing transfer with droplets. “

In the document that serves as a guide to the use of masks in connection with covid-19, dated 5 June, he points out that face shields can be easier to use for people with mental health problems, developmental problems, deafness or hearing problems and children.

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