Yesterday, I saw someone on television stating that out in public, people do not need to wear face masks, something that has been in the media for some time1. This presumably was based on the advice that the coronavirus is only transmissible from person to person over short distances through breathing in droplets spread by coughing or sneezing. This is presumably also the reason behind the 1.5 metre ‘social distancing’ rule. However, now there is evidence that coronavirus may spread by aerosol as well. This is transmission not just by coughed or sneezed droplets, but simply by exhaled air. While the evidence is not conclusive, the degree of evidence required to make it so may take months or years and cost many lives. Aerosol scientist Lidia Morawska from the Queensland University of Technology said “In the mind of scientists working on this, there’s absolutely no doubt that the virus spreads in the air. This is a no-brainer.”2
There is increasing evidence that the number of confirmed cases of coronavirus is a significant under-reporting of the actual number, partly because as many as 50% of cases may be asymptomatic3. In addition, if it is transmitted by aerosol, that adds an increased risk even with social distancing, it would therefore be wise to wear a mask out in public. Even more importantly, if you are infected and are asymptomatic, and if transmission by aerosol is happening, then a mask should be mandatory, so you minimise the risk of infecting others. If you do infect others, they may die. Even though transmission by aerosol has not been conclusively demonstrated, the precautionary principle should operate here, by assuming that aerosol transmission does happen. Therefore, if you want to decrease your risk as much as possible, and the risk to those you see, wear a facemask when out in public.