THE mixed messages on the use of masks by the general public have led to confusion over their role in curbing Covid-19. Adding to this are unverified social media posts that falsely claim wearing masks causes hypoxia (low oxygen uptake within tissues).

If masks should be worn, which type should it be? There are the N95 respirator masks, surgical masks and cloth masks. The fact that masks act as protection for healthcare workers is undisputed. In brief, N95 respirators are for those performing aerosol-generating procedures, while surgical masks are for everyone else.

But what about the public? What is the evidence for its use?

Recently, the Royal Society of Data Evolution and Learning for Viral Epidemics Initiative (Delve) – a British multidisciplinary data analytics group that supports a data-driven approach to learning from different countries’ approaches – published “Face Masks for the General Public”. Putting together their recommendations and evidence derived from other reputable sources, I offer this summary of the evidence for the use of masks in public. Listed are the important facts.

The use of masks in public protects against asymptomatic and pre-symptomatic transmissions (accounting for 40% to 80% of transmission worldwide, especially where community spread has occurred). It’s main role is to protect the user from transmitting the virus in public spaces.

As respiratory droplets can travel 1m to 2m away, masks can potentially prevent the spread of infection from coughing, sneezing, and even talking and breathing. Other modes of spread happens during talking and breathing, with masks offering protection ranging from 50% to 99% of the filtration efficacy.

Masks are best used when in public areas (public transport, for example), confined spaces (grocery stores and offices) and places where social distancing might be difficult. And, they should be worn by individuals down with a respiratory infection.

An infected person has the potential to spark an outbreak at the following rates: indoor/confined spaces (80%) – contact-tracing is slightly easier – and on public transport (34%) – contact tracing is very difficult, thus making geotracking important.

The Delve write-up reported that 30% t0 40% of droplet samples from SARS-CoV-2 patients were detected in unmasked individuals. The numbers were negligible (0% to < 1.5%) from among correctly masked individuals’ samples. Though everyone needs to be obsessive about the use of masks, it is even more so for high-risk individuals with co-morbids (diabetes, or cardiovascular/respiratory/immunology diseases).

As countries look to transition out of lockdowns,, having a society that masks will undoubtedly help, especially knowing that asymptomatic/pre-symptomatic people will soon begin coming into contact with healthy individuals.

The figure below, adapted from Longrich and Sheppard (2020), shows the control obtained among countries with early/late introduction of mask-wearing practices during the Covid-19 outbreak. In countries like South Korea and New Zealand, mask-wearing was supplemented with mass testing, which further aided the reduction of cases.

Local legislation for mask-wearing is vital to help curb the spread. G7 countries (except for Italy and the UK), Taiwan, Czech Republic and China (generally mandatory), and certain states (Jena in Germany), have made wearing masks outside the home compulsory, and this resulted in a reduction in cases or a rapid control of outbreaks. Some states in the US have removed passengers from public transport over adherence failure (making it a civil penalty), and South Korea had interesting policies on the wearing of masks and purchasing limits that might be useful in ensuring the availability of masks for all.

Wearing masks doesn’t mean you care only for yourself; it also means you are concerned for the well-being of the people you come into contact with. However, it will only work (up to 98.5%) if both/multiple individuals within close contact are masked correctly. An educational video on masks and their use and correct application was recently uploaded by Universiti Malaya’s OSHE/Quality team. A study by Liang Tian et al showed that if 60% of people wear masks that are 60% efficacious, it has the potential to reduce a respiratory-linked epidemic.

Masking is in no way an alternative to the strict practices of hand-washing, disinfecting materials, social distancing or staying home when possible. It remains an additional supplement to those protective measures.

A study by Wong et al (2020) showed that masks are not as effective when applied alone. However, it gave a synergistic effect in reducing transmission when coupled with hand-washing and other preventive methods. The false impression of wearing a mask is another issue – remember, it helps prevent particles from being inhaled, and does not get rid of those already on your hands that are still infectious via skin contact with the mouth/nose/eyes. Hand-washing (soap and water, and alcohol-based sanitiser) is a must before and after wearing masks.

The picture below is a very good illustration by www.covid19factcheck.com on the dos and don’ts of wearing masks.

The question that remains is, which type of mask does the public need to use? This is a highly contentious matter among mask advocates. Generally, cloth masks protect against bigger particles like dust, and may have shortcomings where adequate fitting/covering is concerned. Surgical masks (when adequate in a country like Malaysia currently) offer better protection than cloth masks. N95 masks should be strictly left to healthcare workers.

Professional opinions may vary, as theoretically, masks have both advantages and disadvantages. The table below summarises the types of masks, their advantages and disadvantages, and the recommended levels.

The last question is this: if the Yang di-Pertuan Agong can decide to wear a mask, why can’t you? – May 19, 2020.

* Dr Arvinder-Singh HS is a medical officer with a certificate in occupational health, master’s in health research and diploma in football medicine, and is currently pursuing a PhD in community health focusing on adolescent athletes’ health.

* This is the opinion of the writer or publication and does not necessarily represent the views of The Malaysian Insight. Article may be edited for brevity and clarity.