Life Science Coronavirus: Should we all wear face masks? A leading epidemiologist answers key questions
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Coronavirus: Should we all wear face masks? A leading epidemiologist answers key questions

The WHO has reiterated that there is no evidence that healthy people wearing masks in public are protected from COVID-19. Photo: Getty
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The coronavirus pandemic has caused a worldwide shortage of face masks and other personal protective equipment (PPE) that health care workers rely on.

The expert consensus in Australia has been that mask wearing is only necessary for health care workers and COVID-19 patients.

The World Health Organisation (WHO) has reiterated that there is no evidence that face masks provide the general public with protection from COVID-19 infection.

“We don’t generally recommend the wearing of masks in public by otherwise well individuals because it has not up to now been associated with any particular benefit,” Michael J. Ryan, chief executive director of the WHO’s health emergencies program, said recently.

Panic buying of masks can also jeopardise the supply available to frontline health care workers.

However, the consensus on mask wearing is changing in some places, with the United States’ Centre for Disease Control now telling Americans that they can make their own cloth face masks.

So what should we do in Australia?

Professor Mary-Louise McLaws is a Professor Epidemiology of Hospital Infection and Infectious Diseases Control at the University of New South Wales.

She is also a member of the WHO’s expert advisory panel for infection prevention and control preparedness, readiness and response to COVID-19.

Professor McLaws broke down the latest WHO advice on face masks:

“In summary, the WHO Advisory [released on April 7] re-iterates their previous advice, which is that hospital grade masks are needed most by frontline healthcare workers to help prevent the spread of COVID-19,” Professor McLaws explained.

They make it clear that wearing masks is only one of a bundle of infection prevention tools and behaviours that are needed, including hand hygiene.

“There is good evidence that wearing a medical mask is beneficial when you are a healthcare professional and in close contact with people who have COVID-19.

“However, there is no evidence that healthy people wearing masks out in the community generally are protected from COVID-19.”

Read Professor McLaws’ detailed responses to more key face mask questions below:

Q: Not all masks are created equal. Can you give us a 101 on masks?

“There are two types of masks that are effective in filtering droplets from the air: surgical (sometimes called a medical mask) and N95. The design of the surgical mask is tested in a lab to ensure it effectively resists at least 95 per cent of a standard laboratory sized particle and is resistant to blood.

“Our healthcare workers wear surgical masks that repel at least 98 per cent or more of those sized particles.

“Surgical masks provide protection against droplet spread for all healthcare workers providing routine care to COVID-19 patents. A high quality surgical mask can resist smaller particles like the N95 but the N95 mask has the additional safety of a seal against the face while the surgical mask is open at the sides.

“N95 are required when healthcare workers perform an aerosol-generating procedure (causing small particles to be expelled by the patient such as placing a breathing tube into a patient).

“Then there are masks that are being produced that do not conform to these standards and cannot be relied on to prevent the spread of disease through droplets.”

Q: What issues do we currently have with the supply of masks?

“The Australian guidelines stipulate that healthcare workers must use a new mask with each new patient, when the mask becomes moist during caring for the patient, and the healthcare worker must remove the mask when leaving the patient’s room so a new mask must be used for the next patient.

“This means the number of masks used will be very high. Prior to the pandemic the number of patients who required care from a healthcare worker needing to wear a mask was much lower.

“A pandemic creates a surge in patient numbers who can infect healthcare workers and so there is a surge in demand for masks. All countries that have a high number of COVID-19 patients are concerned that their supply of masks will not meet the required demand for masks.”

Q: Can people safely reuse masks?

“During the SARS 2003 outbreak healthcare workers reused their own masks because of the surge in demand for masks associated with the high number of SARS patients and the high number of procedures that required the healthcare worker to wear a mask. They placed their N95 mask into a labelled bag and re-used it the following day until the mask was moist or damp and then they replaced it with a new one. This is not an ideal situation but is an emergency response to severe disruption to the supply chain.

We can’t yet safely reprocess N95 masks because research has reported reprocessing degrades the strands within the mask. The World Health Organisation (WHO) is right now working with global experts to identify the safest method of extending the use of masks until a reprocessing method that does not degrade the mask is identified.”

Q: Can people safely make their own masks?

“No. The production of masks is complex, for example some masks are made up of polypropylene central layers that are charged to prevent penetration of particles and designed to fit the face to provide a seal to prevent small particles from entering the mask.

“Both N95 and surgical masks are lab tested to ensure they filter at least 95-98 per cent of lab particles (referred to as the ‘most penetrating particle’).

“It is understandable that people in places like New York City where the COVID-19 infection rate is very high are nervous and may resort to making their own masks.

“While a mask made out of cotton may provide a small amount of protection from droplets, it is incredibly important that this does not give people a false sense of security.

“If you want to wear a mask, remember it may not be hospital grade. If you wear a mask don’t forget to hand hygiene, avoid touching your face and apply social distancing as these simple actions are still the best ways to avoid being infected with COVID-19 even while wearing a non-hospital grade mask.”

Q: With global shortages reported, what are our options for increasing supply?

“Longer term has to be local production of masks.”