BBC Focus - Science & Technology|May 2020
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At the time of writing, the World Health Organization (WHO) recommends that, outside of health professionals, people should only wear masks if they display symptoms of COVID-19 or are taking care of someone who does. However, more and more countries now recommend that people wear face masks in public places, and WHO is reconsidering its advice based on new evidence.
Prof Jonathan Van-Tam, England’s deputy chief medical officer and a specialist in epidemiology and pandemic preparedness, said in a briefing on 3 April: “…there is no evidence that general wearing of face masks by the public who are well affects the spread of the disease in our society. What matters right now, of course, is social distancing.”
CAN FACE MASKS STOP THE SPREAD OF COVID-19?
“The problem with the new coronavirus is that there’s too little information about exactly how it’s spread, because it’s so new,” says Dr Alexander Edwards, associate professor at the School of Pharmacy at the University of Reading. We don’t know if it’s spread more effectively through contact or coughs and sneezes, he adds.
It is not ethical to expose someone to COVID-19 to study the transmission. Instead, biologists have to make do with other methods. One study from MIT used high-speed cameras to track the droplets expelled in coughs and sneezes. They found that puffs of air carry droplets for up to six or eight metres, for coughs and sneezes respectively. Another study, conducted by aerosol specialist Dr Boris Gorbunov, found that taking wind conditions into account could bring the distance a cough travels up to 25 metres.
“People wear face masks because they think it’s going to protect them from the virus. But the virus isn’t floating around in the air”
Researchers at Hong Kong University and the University of Maryland took another approach. For a study published in the journal Nature Medicine in April, they looked at patients with other types of coronaviruses, along with influenza and rhinoviruses. The researchers collected droplets from the patients’ breath with and without a surgical face mask and counted how many copies of the virus were present. Three out of 10 coronavirus patients had a detectable viral load in their breath without a face mask, compared to none when wearing one.
“It makes perfect sense that if you wear a mask over your face, when you cough, you might expect that the mask would reduce the spread of that cough,” Edwards says. “We don’t actually know how much that reduces it, but the idea of a face mask is a good one.”
WHY AREN’T WE BEING ADVISED TO WEAR FACE MASKS?
“One of the reasons that people wear masks is they think that it’s going to protect them from the virus. But the virus isn’t floating around in the air,” Dr Shunmay Yeung of the London School of Hygiene and Tropical Medicine told the BBC. “It’s probably going to be on my hand because of shaking hands with someone who’s got the virus, and I have transmitted it. I have carried the virus to my face.”
Simply wearing a mask won’t eliminate your risk of catching or spreading the virus. “Remember that some face masks are designed, when you breathe out, to let the air go out as normal, and they only filter the air when you breathe in,” Edwards says. “And a face mask is only as good as it fits.”
A face mask may reduce your risk, but it’s vital that people don’t become complacent because they think they’re protected by a mask. Even the best mask can’t replace social distancing and good hygiene.
A study by MIT tracked the droplets expelled in coughs and sneezes and found that they could travel for six to eight metres
SO, SHOULD WE BE WEARING FACE MASKS?
“I don’t think it’s a bad idea, so long as people understand that they are not magic shields,” Edwards says. If you do wear one, Edwards suggests you keep yourself and those around you safe by behaving as though it doesn’t work.
Finally, ensure you’re not depriving anyone, like health professionals, of the personal protective equipment they need. And importantly, if you have symptoms, don’t go out!
by SARA RIGBY
- Sara is the online assistant at BBC Science Focus.
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