Why we should all be wearing face masks (part 1)

Face masks are a symbol of the pandemic era – a visual metaphor for the tiny, unseen viral foe that could be lurking around any corner. Some opt for a scarf wrapped around their face, others make do with a t-shirt yanked up over their mouth. The more creative hook colourful homemade varieties around their ears, while a lucky few wear distinctive surgical masks or, rarer still, N95 respirators.

While a few months ago anyone wearing a mask in public would have drawn stares in many countries unused to this behaviour, they are now a reminder of the strange times we live in. And as governments around the world start to ease their lockdowns to allow their citizens out to mingle in the wider world again, growing numbers of people are opting to wear face masks in public.

But there is still debate about whether members of the public should be encouraged to wear face masks at all.

In the early days of the pandemic, many governments warned the public against wearing face masks for fear demand would leave frontline health workers without vital supplies and that it may lull people into a false sense of security. Some – such as the US – have since reversed that advice. The state of Utah has said it will provide a free face mask to any citizen who requests it. And other countries such as the Czech Republic, Slovakia, Austria, Morocco, Turkey and Germany have all made wearing masks in public mandatory. It is likely others will follow their lead as they ease restrictions.

But can face masks really make a difference in our battle against Covid-19?

“A key point is that the countries that flattened the curve used masks in public,” says Chris Kenyon, head of the sexually transmitted diseases unit at The Institute of Tropical Medicine in Antwerp, who has examined whether face masks may have played a role in limiting the spread of Covid-19 in certain countries. “These were mostly Asian countries. For some reason, until very recently European experts – Czechia (Czech Republic) excluded – were unable to learn from what worked in Asia.”

To understand why face masks might work, it is important to look at how the virus that causes Covid-19 spreads in the first place.

Once it has infected someone, the Sars-CoV-2 virus responsible for the disease hijacks their cells to replicate itself. As it multiplies, these new virus particles then burst out of the cells and become suspended in the bodily fluids in our lungs, mouth and nose. When an infected person coughs, they can send showers of tiny droplets – known as aerosols – filled with the virus into the air.

A single cough can produce up to 3,000 droplets. There are fears the virus can also be spread simply through speaking. One recent study showed that we spray thousands of droplets invisible to the naked eye into the air just by uttering the words “stay healthy”.

Once out of our mouths, many of the larger droplets will quickly settle onto nearby surfaces while smaller ones remain suspended in the air for hours, where they can be breathed in. While the behaviour of the virus-filled droplets in rooms with air conditioning and outside environments are less well understood, they are thought to settle on surfaces more quickly in disturbed air. There are also some reports that the coronavirus can spread through ventilation systems in buildings. (Read more about how long coronavirus survives on surfaces.)

When an infected person coughs, they can send showers of tiny droplets – known as aerosols – filled with the virus into the air

The Sars-CoV-2 virus has been found to survive in these aerosol droplets for at least three hours, according to one study by virologist Neeltje van Doremalen and her colleagues at the US National Institute of Allergy and Infectious Diseases, Hamilton, Montana. But a more recent, but as yet unpublished study, has found that the Sars-CoV-2 virus is still infectious for more than 16 hours after being suspended in aerosol droplets. It found the virus was “remarkably resilient in aerosol form” compared to other similar coronaviruses they studied.

Together, they suggest that in the right conditions, the virus can linger in the air for several hours and still infect people if breathed in. And in indoor environments, they seem to be particularly prone to spreading through the air.

An unpublished analysis of 318 outbreaks of Covid-19 in China showed that it was most commonly transmitted in indoor environments, particularly in people’s homes, but also on public transport, in restaurants, cinemas and shops. They found just one example where the virus appeared to have been transmitted while people were outside.

Genetic material from Sars-CoV-2 has also been detected in the air in toilets and rooms used by people infected with Covid-19. One study of a cluster of cases that occurred in a restaurant in Guangzhou, China, suggests that in poorly ventilated spaces the virus can spread to people sitting in the immediate vicinity through airborne aerosol droplets.

Part two of Why we should all be wearing face masks will be published in Tuesday’s edition.

Source: https://www.bbc.com/future/article/20200504-coronavirus-what-is-the-best-kind-of-face-mask