Consumer Watch: Experts warn visors do not stop spread of coronavirus
Sensible use of face masks for non-medical purposes will not prevent you from getting Covid-19 but it might protect those around you. And if enough people follow the advice, infections could be brought down.
But experts have expressed concern about face shields or visors, which are becoming increasingly popular as an alternative to masks, because they do not provide adequate protection for both wearers and others.
The Health Department, Covid-19 ministerial advisory committee chairperson Professor Salim Abdool Karim and other medical experts have stressed that wearing a cloth mask in public, physical distancing and hand hygiene remain the most important ways of preventing the virus’s spread.
The reasoning is that it's not to protect you - it’s to protect others.
More than 50 countries across the world have made masks compulsory. Although experts differ on the efficacy of the non-medical cloth masks, combined with phjysical distancing and hand sanitising, masks are viewed as part of the puzzle in the fight against the coronavirus.
First line of defence
Associate Professor Sudesh Sivarasu, a biomedical engineer from UCT, and his team of researchers have worked on a variety of biomedical devices, including a face shield that can be made easily with household items.
The ViZAR was designed by postgraduate researcher Matthew Trusler, in collaboration with Sivarasu, as well as Dr Stephen Roche of the UCT Division of Orthopaedic Surgery, Professor Salome Maswime and Dr Tracey Adams of the UCT Division of Global Surgery, and Saberi Marais from UCT Research Contracts & Innovation.
Approved by the South African Health Products Regulatory Authority, the ViZAR acts as a first line of defence between the user and any infectious, airborne particles, offering protection against harmful aerosols, and preventing possible cross-contamination from users touching their faces.
It’s a transparent shield with a foam lining at the top of the visor that sits snugly against the wearer’s forehead, drops low and wraps around the face.
While the team streamlined their energy around clinical use, they also produced economical designs for manufacturers, who supply retailers and other clients. Sivarasu says visors, or face shields, should never be worn instead of a mask.
And he warns that many commercially available visors are too flimsy and poorly designed to be of any benefit. Many shield only a part of the face, not the sides or even forehead.
“Visors are only, at best, a first line of defence item,” Sivarasu explains.
The Royal Academy of Engineering says the plastic sheets used for commercial application should be no less than 250 microns thick and 400 microns for clinical use.
“But if you’re going to reuse it repeatedly, you need a more sturdy design, which might render it quite rigid and uncomfortable.”
Sivarasu says his team’s design is around comfort, but it is not intended to be worn instead of a mask.
“The most important feature of a visor prevents you from touching your face. This is like a peripheral protection. Even if you wear a mask, you’re still exposing your eyes. It gives you a false sense of security. You have to be careful when choosing a visor - and it’s not a case of one or the other,” he says.
Masks offer protection from viral particles that might enter through the mouth and nose, but not the eyes. They provide a false sense of security and are often poor-fitting.
Visors, on the other hand, are said to be less claustrophobic than goggles, provided they are made to World Health Organization specifications. They don’t steam up, don’t interfere with vision (although some flimsy shields do), and a study published in the Journal of the American Medical Association (Jama) has shown that they reduce immediate viral exposure by 96%. An April editorial in Jama supported face shield wearing, because they can be reused, easily cleaned, comfortable to wear, and reduce wearers from touching their faces.
“People wearing medical masks often have to remove them to communicate with others around them; this is not necessary with face shields,” Dr Eli Perencevich, from the University of Iowa said.
However, that study also revealed that visors became less effective after 30 minutes, once the viral particles had dispersed into an enclosed space.
Professor Heather Zar, the chair of the Department of Paediatrics and Child Health at Red Cross Children’s Hospital, says the evidence is that small viral particles hang in the air and are breathed in. “This is important in terms of spread - visors are important for the first initial contact but not effective in terms of aerosol spray. They should only be used as additional PPE.”
No masking it
During an update on the safe reopening of schools in the Western Cape, Professor Mignon McCulloch, the chairperson of the South African Paediatric Association, said paediatricians were in favour of children’s return to school because the benefits (educational, psychological, food security and safety) outweighed Covid-19 risks.
But mask-wearing, hand sanitising, physical distancing and environmental cleaning were non-negotiables: “Masks are the one thing that really makes a difference. Visors only stop big droplets from spreading; they do nothing to stop the aerosolised virus.”
Compared to face masks, visors do not stop droplets from breath, speech, coughs or sneezes drifting into the wearer’s face and they are unlikely to do a good enough job of containing exhaled breath droplets.
McCulloch says the Czech republic, which has significantly slowed the spread of the virus, was the first in Europe to mandate mask wearing.
“Masks fundamentally protect the transmission of you to others. So, when both people have a face mask, I protect you, you protect me. It’s a sign of respect. In Taiwan, South Korea and other parts of Asia, mask-wearing is part of the culture so children wear them for a significant amount of time, without any harm. As the evidence stands, we say definitely masks.”
* Georgina Crouth is a consumer watchdog with serious bite. Write to her at [email protected], tweet her @georginacrouth and follow her on Facebook.
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