Friday 10 April 2020

Face masks cannot stop healthy people getting Covid-19, says WHO

Organisation’s evidence review shows wearing mask outside does not prevent infection

The World Health Organization has held off from recommending people wear face masks in public after assessing fresh evidence that suggested the items may help to contain the pandemic.

The WHO reviewed its position on masks in light of data from Hong Kong indicating that their widespread use in the community may have reduced the spread of coronavirus in some regions.

But in updated guidance published on Monday, the organisation maintained that while masks could help limit the spread of the disease, they were insufficient on their own. There was no evidence that wearing a mask in the community prevented healthy people from picking up respiratory infections including Covid-19, it said.

Prof David Heymann, of the London School of Hygiene and Tropical Medicine, who chaired the WHO’s scientific and technical advisory group for infectious hazards, said that unless people were working in healthcare settings, masks are “only for the protection of others, not for the protection of oneself”.
People wearing face masks in Hong Kong. The WHO reviewed its position on masks in light of data from Hong Kong. Photograph: Jérôme Favre/EPA

The committee acknowledged the virus can be transmitted by people who do not have symptoms, but said the virus must still spread via droplets or contaminated surfaces, which physical distancing and handwashing are intended to minimise.

According to the updated advice, people with coronavirus symptoms should wear a face mask, self-isolate and seek medical advice as soon as they start to feel unwell, while those caring for them should wear a face mask when they are in the same room.

The WHO guidance on healthy people wearing masks in public appears to conflict with recent advice from the US Centers for Disease Control and Prevention, which urged the US public to wear cloth face coverings in pharmacies, groceries and other public places where physical distancing can be hard to maintain.

Heymann said masks could create a false sense of security that could end up putting people at greater risk. Even with the mouth and nose fully covered, the virus can still enter through the eyes.

“People think they are protected when they are not,” he said. 

“Healthcare workers, in addition to the masks, wear visors too, to protect the eyes.”

Another concern is that people may contaminate themselves when they adjust, remove and dispose of their masks.

The WHO said people who chose to wear masks in public should follow its advice to ensure they were using them safely. It said countries that recommended masks for the general population should set up studies to monitor their effectiveness.

William Keevil, a professor of environmental healthcare at the University of Southampton, said governments felt under pressure to be seen to be doing something, even if it was a waste of time and valuable resources.

“Cloth masks and poor quality surgical face masks will not filter fine respiratory droplets, and certainly not aerosols, which some are now claiming to be an infection risk,” he said. “The major question that needs to be addressed is: what about protecting the eyes, a known route of entry?.”

Dr Elaine Shuo Feng, an epidemiologist at Oxford University, supports the US stance on face masks and said it would be sensible for people who may have been exposed to the virus to wear face masks outdoors because of the risk of passing on the virus.

“It would be helpful if high-risk people – elderly, people with chronic conditions – wear a face mask if they can’t avoid crowed areas, because these people have the highest risk of severe outcomes such as ICU/death if infected,” she said.

(Source: The Guardian)

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