A really good overview of the contribution of masks to suppressing the spread of COVID-19 has just been published in The Conversation. It is a very good article and I thoroughly recommend reading it. In this post, I want to concentrate on one of the seven points that are mentioned there.
Countries that quickly introduced masks – primarily Asian countries with SARS experience – seemed to be much more successful in suppressing the initial outbreak in March-April 2020.
This figure comes from a very interesting paper by Lefler et al, 2020, which analysed data from March-April 2020 and categorised the outcomes of the pandemic (cases, deaths) in relation to lockdowns and mask-wearing. Essentially, this figure shows that countries that introduced masks earlier suffered much lower deaths during the initial period of the epidemic.
This reduction could have been due to other factors than just mask wearing. However, Lefler et al, 2020 actually consider these different factors (like lockdown, obesity, age) and find that mask wearing – or not – was the main factor determining the death rate in these countries (in fact the most significant one).
The authors of this study include a graph that demonstrates that the longer it took for a country to introduce masks, the higher the death rate was:
Here, the start of the outbreak is 5 days before the first case reported, or 23 days before the first death (whichever was earlier) and the duration of the outbreak without masks is defined as the time from the start of the country’s outbreak until masks were recommended or until April 16 (whichever came first).
The line is the linear regression – note the logarithmic scale of the vertical axis, meaning that the differences were actually quite large – about 1,000 times from one end of the regression line to the other. In other words, countries that introduced the mask 12 weeks or so into the outbreak suffered 1,000 times higher mortality than those that started immediately.
Or, each delay of 2 weeks from the onset of the outbreak causes a 10-fold increase in per-capita mortality.
We of course need to be careful in the interpretation of the results. There were certainly many factors that influenced the outcome of the first wave. I have not seen an analysis extending this study to later stages of the epidemic. But, as The Conversation article reports, there have since been multiple lines of evidence showing that the virus spreads through the air (either by droplets or by aerosol) which points to masks as a key way to control.
Why is it so important now to read into this – quite old by current standards – paper? There is a current discussion in the UK on whether masks should continue or not when all other regulations are dropped on July 19th. SARS-CoV-2 is airborne and it is still spreading, so masks should continue to be worn, especially in places of high risk.
Moreover, even where and when it is not compulsory to do so, it should be socially acceptable for those who feel at risk – or those who might be ill – to wear them.
A disclaimer: I do not like wearing a mask, although I have invested in a high-quality one by Airinum having worn similarly excellent homemade masks at the start of the epidemic. But I am really puzzled by such a strong resistance to the idea of mask-wearing. Even in Western countries, we are taught from childhood that we should be doing things that protect us – and others – from risk, even if it comes with a cost. “Do to others what you would have them do to you” is the Golden Rule widely accepted in our culture. How is it then that so many people in the West feel so strongly against mask-wearing?