Fearures, Health and Society Editor
The World Health Organisation (WHO) has published an updated guidance on the use of face masks for control of COVID-19.
In his opening remarks at a media briefing on Covid- 19 last Friday, WHO Director-General Dr Tedros Adhanom Ghebreyesus said the guidance is based on evolving evidence, and provides updated advice on who should wear a mask, when it should be worn and what it should be made of.
He said WHO has developed this guidance through a careful review of all available evidence, and extensive consultation with international experts and civil society groups.
“I wish to be very clear that the guidance we are publishing today is an update of what we have been saying for months: that masks should only ever be used as part of a comprehensive strategy in the fight against COVID.
“Masks on their own will not protect you from COVID-19,” he emphasised.
He said the updated guidance contains new information on the composition of fabric masks, based on academic research requested by WHO.
“Based on this new research, WHO advises that fabric masks should consist of at least three layers of different material. Details of which materials we recommend for each layer are in the guidelines.”
According to the latest guidelines, cloth masks should consist of at least three layers of different materials: an inner layer being an absorbent material like cotton, a middle layer of non-woven materials such as polypropylene (for the filter) and an outer layer, which is a non- absorbent material such as a polyester or a polyester blend.
“Fabric cloths (e.g., nylon blends and 100 percent polyester) when folded into two layers, provides 2-5 times increased filtration efficiency compared to a single layer of the same cloth, and filtration efficiency increases 2-7 times if it is folded into 4 layers. Masks made of cotton handkerchiefs alone should consist of at least 4 layers, but have achieved only 13 percent filtration efficiency. Very porous materials, such as gauze, even with multiple layers will not provide sufficient
filtration; only 3 percent filtration efficiency,” read the new guidelines.
The new guidelines stress that is important to note that with more tightly woven materials, as the number of layers increases, the breathability may be reduced.
Therefore, a quick check for breathability may be performed by attempting to breathe, through the mouth, and through the multiple layers.
WHO officials stressed that the new advice is an update to previous guidance, and that masks should only ever be used as part of an overall comprehensive strategy.
They also provided guidance on how to wash and maintain a fabric mask.
“Our guidance also explains how to use a mask safely.
“People can potentially infect themselves if they use contaminated hands to adjust a mask, or to repeatedly take it off and put it on, without cleaning hands in between,” said Dr Ghebreyesus.
He added that masks can also create a false sense of security, leading people to neglect measures such as hand hygiene and physical distancing.
“I cannot say this clearly enough: masks alone will not protect you from COVID-19.
“Masks are not a replacement for physical distancing, hand hygiene and other public health measures. Masks are only of benefit as part of a comprehensive approach in the fight against COVID-19.”
Outlining what has not changed, Dr Ghebreyesus said WHO continues to recommend that people who are sick with symptoms of COVID-19 should remain at home, and should consult their health care provider.
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He also said people confirmed to have COVID-19 should be isolated and cared for in a health facility and their contacts should be quarantined.
“If it is absolutely necessary for a sick person or a contact to leave the house, they should wear a medical mask.
“WHO continues to advise that people caring for an infected person at home should wear a medical mask while they are in the same room as the sick person,” he said.
He also said WHO continues to advise that health workers use medical masks and other protective equipment when dealing with suspected or confirmed COVID-19 patients.
Explaining what is new, he said in areas with widespread transmission, WHO advises medical masks for all people working in clinical areas of a health facility, not only workers dealing with patients with COVID-19.
“That means, for example, that when a doctor is doing a ward round on the cardiology or palliative care units where there are no confirmed COVID-19 patients, they should still wear a medical mask.
“Second, in areas with community transmission, we advise that people aged 60 years or over, or those with underlying conditions, should wear a medical mask in situations where physical distancing is not possible,” he added.
Third, Dr Ghebreyesus said WHO has also updated its guidance on the use of masks by the general public in areas with community transmission.
“In light of evolving evidence, WHO advises that governments should encourage the general public to wear masks where there is widespread transmission and physical distancing is difficult, such as on public transport, in shops or in other confined or crowded environments.”
He added that the cornerstone of the response in every country must be to find, isolate, test and care for every case, and to trace and quarantine every contact.
“That is what we know works. That is every country’s best defense against COVID-19. WHO will continue to provide the world with advice based on the most up-to-date evidence, as part of our commitment to serving the world with science, solutions and solidarity,” he said.