To mask or not to mask?

This week’s expert:
Professor Raina MacIntyre, Head of Biosecurity at the Kirby Institute, University of NSW.

Drawn from an interview with Prof MacIntyre by Dr David Lim on the Healthed podcast Going Viral.

• There is evidence supporting the effectiveness of wearing a face mask for the prevention of contracting and transmitting a viral respiratory infection in three of the following groups:
a. well people in the community
b. sick people
c. health care workers

• There have been no randomised controlled trials specifically looking at the effectiveness of face masks in preventing the transmission of COVID-19, more commonly it relates to the transmission of other viral respiratory infections such as influenza.

• Despite earlier advice that wearing a facemask was only useful in preventing an infected person transmitting the virus to others, there is now evidence that wearing a mask can actually protect an unaffected person from contracting the virus.

• Research shows respirators (N95 masks) protect health care workers more than the standard surgical masks.

• There is also evidence that seasonal coronaviruses are more likely to be transmitted via aerosol particles than other respiratory viruses such as influenza. It appears that even the normal exhaled breath can transmit infection with coronavirus, rather than requiring the forced expulsion of breath as seen with a cough or sneeze.

• A recent meta-analysis (published in the Lancet) of all trials looking at facemask effectiveness, including ones involving previous SARS and MERS outbreaks, showed that any kind of facemask use in the community was 85% protective. Further analysis showed the use of N95 mask was 96% effective, and the common surgical mask was 67% effective.

• The WHO has changed from its original position which was that there was no reason for healthy people to wear masks to avoid contracting COVID-19. The WHO now suggests face masks be considered, especially in situations where social distancing isn’t possible.

• Given that there exists a high incidence of asymptomatic and pre-symptomatic transmission of COVID-19, it is advisable that all Australians should wear a mask when out in public, especially in areas where there are known outbreaks – namely Victoria.

As restrictions ease and people emerge from their social isolation, we need to promote the concept of a social contract. In exchange for our renewed freedoms, we need to agree to three basic conditions – wear a mask, keep our distance from others, and download the CovidSafe app to assist in contact tracing should the need arise.

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