COVID-19: To mask or not to mask?
In early February 2020, I was catching a flight back from Singapore to Germany, after briefly attending my best friend’s wedding in Kuala Lumpur. I was constantly having a mask on at the airport, during the flight, and all the way until I touched down in Germany. While I was commuting on the train back home from the airport, I could see people throwing that stigmatized glance at me, it was not hard for me to guess that association between a mask, an Asian look, and the coronavirus.
Fast forward a few months later, masks are now compulsory in Germany when in public transport or in enclosed areas like supermarkets or shopping malls. The same rule applies to most parts of Europe and is now a common sight for people to stay masked in public. But across the Atlantic, people are getting more polarized over the debate — to mask or not to mask. Some even to great length by testifying in congress:
This article looks to rapidly review some of the publications in peer-reviewed journals (wherever available) and of pre-peer-reviewed manuscripts to explore scientific evidence in wearing masks against Sars-CoV-2 — if the mask can really shield us from the virus.
How does the Covid-19 virus transmit?
Covid-19 is a disease caused by the coronavirus named Sars-Cov-2. This virus is similar to earlier outbreaks caused by the same family of coronavirus, like SARS and MERS. Most people infected with the virus will experience mild to moderate respiratory illness but can be detrimental for older people and people with underlying medical conditions, as the virus can quickly complicate health conditions and accelerate respiratory failure.
COVID‑19 is a novel disease, and many of the details of its transmission are still under investigation. According to WHO, current evidence suggests that COVID-19 can spread through direct or indirect contact. Direct contact usually refers to close contact (within 1 meter) with infected people over a prolonged period of time (for approximately one hour or more). The close proximity allows the spread of the virus via direct physical contact with saliva and respiratory droplets or secretions, which are expelled when an infected person coughs, sneezes, talks or sings. These droplets if dropped on a surface and later come into contact with a susceptible host is known as indirect contact or more formally a fomite transmission.
There is also mounting evidence that airborne transmission can be a potential third transmission route and the risk is acknowledged by WHO in the event of indoor crowded spaces. There are at least 4 independent publications that outlined the importance of airborne transmission in a large-scale gathering which subsequently resulted in an infectious cluster. 4 different indoor settings are investigated — in a restaurant, during choir practice, in a tour bus, and in fitness classes.
Masks against coronavirus
Be it droplets or airborne transmission, preventive measure is required to protect ourselves, especially in public when interactions with the general public are inevitable. Masks have been proven to be the “first line of defense” against any immediate risk of infectious droplets and to offer some degree of protection against the finer aerosols, subjected to ambient conditions (wind and airflow) as well as the filtration efficiency of the masks.
As the pandemic has put a strain on mask supplies, many have turned creative to homemade masks with common fabrics found in the household. Cloth masks also offer additional benefits such as sustainability through re-use, thus limiting costs, and reducing environmental waste. But, how effective are these masks? The results of an experimental setup using aerosol particle generator on 15 different types of fabrics have concluded 4 important findings (for filtering nanoparticles of more than >300nm; respiratory droplets are generally classified with diameters >5μm and aerosols <5μm):
- N95 and surgical masks are still the gold standards for high filtration efficiency (>99%) but only if being worn correctly, i.e. without gaps between the mask and face contour. Poor-fitting of these masks can reduce filtration efficiency by up to 80%!
- Fabrics of high thread count (TPI) also offer surprisingly high filtration efficiency, 600 TPI cotton offers 5 times as much performance to 80 TPI cotton (98% VS 14%).
- Increasing the layers of fabrics also proven to be effective. More layers can in fact complement fabrics of lower thread count. For natural silk, 4 layers are 30% more effective than 1 layer (88% VS 56%).
- Fibers in natural silk can also be electrostatically charged, offering an extra layer of protection.
A snippet of the results can be seen in the following illustration.
The numbers don't lie
There are now over 100 countries that have implemented mask requirements. If we look at the number of cumulative cases 20 days after the first 100th confirmed cases in developed countries with a well-established healthcare system, we can already observe a stark difference between countries with a culture of universal mask usage versus those without.
Most European countries also mandated a nationwide masks requirement in public at a later day as the pandemic started to spiral out of control. While the debate on the effectiveness of masks continues to remain controversial, most numbers from Asian countries with universal mask usage remain much lower than of their European counterparts. Although between-region comparisons do not allow for direct causal attribution, making mask-wearing mandatory seems to be a low-risk measure with a potentially large positive impact. 30 days after the implementation of masks requirement, the curves do actually started to flatten out.
Existing literature and available data do offer some positive evidence in the widespread use of masks to fight against coronavirus. However, to fully harness the benefits of masks requires the collective efforts of everyone in the community. Contrary to clinical settings, where masks are normally used as part of the PPE (personal protective equipment), community face masks actually help to contain the spread of the virus by limiting the infectious droplets from spreading around. Thus, it is not always about protecting yourself but also protecting the people around you.
It is also important to note that when masks are made mandatory in public, it was normally implemented in tandem with social-distancing and a strong advisory for frequent hand-washing.
The three measures — Face masks, social-distancing, and hand-washing are like a protective triad , with the virus trying to get in. If one of the branches is missing, then you are not protecting the whole thing. And if everyone is doing it, we all protect each other. — Shan Soe-Lin, Lecturer in global affairs, Yale