With the relaxation of confinement regulations and the reopening 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 cloth face masks in different models, patterns and colors.
However, in recent weeks, a new element of protection has begun to be seen on the streets: it is a clear plastic face shield or protector, which until recently was only used by healthcare personnel or in medical or hospital settings.
At first glance, these protective shields look more comfortable than masks: not being in direct contact with the nose and mouth, it is easier to breathe, speak, give less heat and are definitely less claustrophobic.
But do they protect us as much as a face mask? Can we replace one with another?
Advantage
According to a recently published opinion piece in JAMA, the journal of the American Medical Association, these displays have a number of advantages.
“They are comfortable to wear, protect entry portals froml virus and they reduce the potential autoinoculation, since they avoid that the user touches his face, “says the text prepared by Dr. Eli Perencevich, an infectious disease specialist at the University of Iowa, and two other researchers.
Unlike the masks you don’t have to take them off to facilitate communication, They can be reused indefinitely if they are not damaged, and can be easily cleaned with soap and water or common disinfectants, the article points out.
The authors do not advocate the use of this screen as the only measure, but they do consider that it may be one more element in a coronavirus containment strategy that includes handwashing, social distance, and contact tracking.
On the other hand, they add, face screens cover a much wider area of the face, including eyes, which are another route of entry for SARS-CoV-2.
Wider protection
According to a 2014 cough simulation study, a good plastic screen can reduce total exposure to cough droplets and aerosols (the tiny droplets) in a 96% at a distance of 46 cm.
But, with the smaller sprays, the shield was less effective, blocking 68% immediately after coughing, and only 23% in the next 30 minutes, as these smaller sprays can float under the visor. , in the space where inhalation occurs.
In the opinion of Julian Tang, professor in the Department of Respiratory Sciences at the University of Leicester, in the United Kingdom, facial displays are generally quite effective, but acknowledges that comparing them directly with surgical masks is difficult, and that the studies that have been done so far have only done so to a limited extent.
If we are going to use them, the most important thing to keep in mind is “how far the protector bends to cover ears (if there is a space, aerosols could enter that way and cause an infection) and how far it extends below (to protect ourselves from the floating aerosols that we can inhale under the protector), “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 drops or aerosols that can fall from above.
Neither alone nor in the community context
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 whatever reason – it is always better to use it than to go with it. the bare face.
Aaron Glatt, director of the department of medicine at Mount Sinai South Nassau Hospital in the United States, believes that the benefits of the screens vary depending on who uses them.
“We recommend its use in the case of a health workerFor example, you should enter the room of a patient who has or is suspected of having covid-19 and is not wearing 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 eyes of the healthcare worker with glasses or a face shield, over the mask.”
“But in a community context, we recommend the mask (and not the screen), because it is more effective in preventing the virus from spreading to surrounding areas. If the person wearing the mask is expelling virus, the drops will be trapped by the mask. “
In short, “it is a most effective mechanismGlatt adds.
The US Centers for Disease Control and Prevention (CDC) also does not recommend its use in the context of everyday life or as a substitute for fabric mouth masks.
But in case someone decides to wear it without a mask underneath, they should make sure that it covers the sides of the face and extends below the chin.
Protection against aerosols
Although face shields prevent the droplets from passing, since their contour is not sealed to the face, they allow the passage of a certain number of sprays.
The World Health Organization (WHO) recently acknowledged, in response to an open letter published by more than 200 scientists, that there is increasing evidence that the coronavirus can be spread by these tiny airborne particles.
“The airborne cannot rule outI know in stages with crowds or in closed and poorly ventilated places, “said a representative of the organization on Wednesday.
However, this transmission route, explains Luis Ostrosky, professor of infectious diseases at the UTHealth McGovern School of Medicine in Houston, USA, to the BBC World. it is not the main one.
“We believe that the primary transmission route of the 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 that leaves the rest of your face exposed “.
“The other is with a face shield, which covers your entire face,” says Ostrosky.
“Aerosols may contribute to transmission in closed environments, particularly in situations such as medical procedures, but that is a controversial issue.”
“So there is a growing consensus among epidemiologists that the screen can be a very good alternative to protect themselves within a community context. “
In Ostrosky’s opinion, they are particularly beneficial for young children because they reveal facial expressions.
“I think they will be an element key to reopening schools“.
The WHO, for its part, points out that, for the general public, screens can be considered as an alternative in the event that there is a shortage of non-medical masks, but says they are “inferior to the masks regarding the prevention of transmission by drops. “
In the document that serves as a guide for the use of masks in the context of covid-19, dated June 5, points out that facial displays may be easier to use for people with mental health disorders, problems with development, deafness or hearing difficulties and children.
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