The Case for Universal Adoption of (cloth) Face Masks during COVID-19 Pandemic

During COVID-19 many Asian countries have adopted universal masking but health authorities in western countries do not advise healthy people to wear masks. Does it work or doesn’t it work? Are we Asians just crazy or is there some solid science to say that even healthy people should wear face masks during an epidemic? (EDIT: Since posting, universal cloth masking has gained significant momentum — as of 3rd April, Los Angeles, New York City have already reversed previous guidance and promoting universal cloth masking, 4th April: US Center for Disease Control (CDC) also changed stance.)

After reviewing academic research and consulting leading epidemiologists, there is scientific reason to believe that universal masking can help reduce transmission rates in a population. Once case curve has flattened and authorities try to strike a new balance by loosening some restrictions, universal masking should be considered by western countries as part of the toolkit in the global war to contain SARS-COV-2.

The science is not perfect so there is a hurdle for authorities to change their public guidance but as individuals, we can make our own judgement based on the facts below. Surgical masks are more effective than cloth masks but a cloth mask is emphasised in order to not exacerbate supply problems for healthcare professionals. (See research in efficacy of cloth masks). If you live in a country where there is enough for everyone, then, by all means, wear surgical mask.

Let’s start by addressing the primary arguments for why authorities are currently not advising the general public to wear masks when healthy. Let me just clarify that we are not talking about N95 masks here — those should no doubt be exclusively reserved for those operating on the front-lines and for immuno-suppressed individuals. We are talking about surgical/cloth masks:

Types of Masks

Arguments Against Universal Masking

1. Supply Shortage: The biggest factor, I believe, influencing public health authorities to discourage the use of masks by healthy public is due to supply. Regardless of how well it works, all N95s and surgical masks must go to front-line medical professionals and others with urgent needs without question. There is no way currently to provide 300 million masks for every US citizen everyday.
2. Unproven effectiveness in wearer protection: There are two main ways a mask can theoretically protect the wearer from infection. Physically blocking large droplets caused by sick people speaking/coughing in your vicinity or filtering out airborne aerosols which can remain suspended in the air for hours after the sick person has departed. Part of the difficulty in proving efficacy of masks is that there is currently no data showing what percentage of infections happens via which route— is direct transmission via large droplets? Is it indirect transmission via touching objects? Is it airborne aerosol particulates that sick people breathe out into the air? Experts agree that masks are effective in blocking large droplets. Experts are split as to how well surgical masks can filter airborne aerosols. Unlike N95s, surgical masks are not made for this purpose. They do not seal around your face and is leaky around the edges. Many attempts at random controlled trials or observational studies are non-conclusive and it is arguable how transferable those conclusions are for a new virus with different transmission properties (particle size, peak viral load time vs. symptom onset, incubation period etc.).
3. Improper use: Another concern often cited is that the public do not know how to use masks properly. They touch the outside of used masks or put the mask under their chin while talking on the phone. Under these circumstances, if the mask was indeed effective in blocking virus particles, the virus would be sitting on the outside of the mask and hence improper use might actually increase one’s exposure.
4. False sense of security: In addition, the general public may develop a false sense of security, thinking that they are safe wearing the mask and hence reduce their compliance to other more important measures — such as social distancing, avoid touch face, hand washing etc.

These are pretty compelling reasons and so it is understandable that the CDC does not advise healthy public to wear masks and, likewise, the US Surgeon General shouting on twitter for people to stop buying masks.

That being said, I believe there is a case to be made that there are even more compelling reasons to encourage universal masking.

Arguments For Universal Masking

1. Significant pre-symptomatic / mild symptom transmission: Currently, this is the strongest reason for universal masking because the masking protects the environment from transmission by pre-symptomatic people. The research around this topic is still evolving day by day and the research is so new that many have not been peer-reviewed. Despite the uncertainty, the fact that both generation interval and virological methods corroborate one another gives me some confidence that this is a valid assumption. One pre-print study conducted by Belgian and Dutch researchers estimates that 32% — 67% of cases in Singapore and 50% —76% of cases in Tianjin, China were caused by pre-symptomatic transmission
2. Masks are effective to prevent sick people from infecting others: Arguments presented against the use of masks by healthy people assumes that people know if they are healthy or sick. It also assumes that people will self-isolate or wear masks if presented with trivial symptoms like a tickle in the throat. These assumptions are not valid based on what we know today. For many under financial or work pressure, they feel they cannot afford to self-isolate (case in point in this NYT article). The social stigma that masks should only be worn by sick people means that people who present trivial symptoms will be reticent to wear mask for fear of discrimination. There is expert consensus that surgical masks work in preventing infected people from spreading the disease to others. So the reason to wear a mask is not only because it might provide some personal protection, but also from a civic duty standpoint, you stop yourself from being a transmission vector in case you are unknowingly infected.

1. DIY Cloth mask made from certain materials is a viable alternative — (When made with the right materials, performance of cloth mask can be similar to surgical mask for blocking outbound droplet at ~50%, ~58% efficient at blocking inbound aerosol, ~17% efficient in blocking outbound aerosol): Cloth masks work almost as well as a surgical mask for blocking outbound droplets (>3um) from getting out of the mask of a sick person coughing, demonstrated in a study by researchers at Cambridge University. There are two other studies that focuses on airborne aerosol particulates getting in/out. Cloth masks made from the right everyday materials are able to block inbound aerosols from entering the mask at ~50% (Cambridge study shows 50% with 100% cotton T-shirt material Netherlands study shows 50% with tea cloth). Performance is worst for outbound aerosol, Netherland study showed the tea cloth mask was only able to block aerosols from leaving mask at10–20% efficiency. Obviously this is highly simplified analysis, for more details — go here.

These graphs below were adapted from a study published by researchers in the US where they challenged different cloth materials with particles of different sizes at a flow rate that simulates quiet breathing. There are two important takeaways. The red lines marked indicate the size of the SARS-CoV-2 virus: firstly, there are cloth materials that are able to filter almost 60% of 120nm particulates (Aquis Towel). Secondly, even within a fabric category: towel, sweatshirt, Scarf etc. there is significant variation.

Source: “Simple Respiratory Protection — Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 0.02–1um size Particles” published by the US National Institute for Occupational Safety and Health/National Personal Protective Technology Laboratory in June 2010

From US Center for Disease Control COVID-19 guidelines:

In settings where facemasks are not available, Health Care Professionals (HCP) might use homemade masks (e.g., bandana, scarf) for care of patients with COVID-19 as a last resort. However, homemade masks are not considered PPE, since their capability to protect HCP is unknown.

(EDIT: came across this excellent Medium article after posting — written by Sui Huang which has more details).

4. Social and Psychological benefits: There are multiple arguments here — none of which are easily quantifiable:

• Prevent discrimination of those who wear masks if everyone wears mask: One could argue that if one is showing symptoms, you should be at home. However, pragmatically speaking, we know that this disease manifests very mildly in most cases and hence it is easy for someone to mistake it as just a tickle in the throat or just common cold. Secondly, many are under tremendous financial pressure to provide for their families — being out of action for two weeks can be devastating for these families. Hence, even if they have mild symptoms, they may not choose to isolate themselves. In addition, some people may look well but are immuno-suppressed and should be wearing a mask even though they are not yet sick. In these situations, it is highly beneficial to have a social environment where such individuals will not be stigmatized by wearing a mask.
• Symbol of solidarity and support: In Hong Kong, wearing a mask at times like these is a signal that you are aware of the deadly potential of the virus, you are willing to give up some personal comfort to protect others and willing to make personal sacrifices to reduce community spread even if it is an unproven/small impact. For everyone else not wearing masks, it is a reminder about how seriously the community is taking the issue and creates social pressure to not just comply with masking but for all the other protective measures as well. It is a social protocol that brings us together in difficult times.
• Constant reminder to be vigilant, reduce hand to mouth/nose touch: With a physical barrier on your face, it is a constant reminder that this is not life as usual. It puts your mind in a state of vigilance with potential benefits to hand-washing, not shaking hands, maintaining personal distance. In addition, with a physical barrier, it is more difficult to touch your nose and mouth with your hands, which may be contaminated. Tests reveal that an average person touches their face 1–2 times every 3 minutes spontaneously that is difficult to control. Given that you have to remove your mask to reach your face, it gives an extra second to rethink whether you really need to touch your face and if so, sanitize first.

5. Network Effect: universal mask wearing creates a network effect that is greater than the sum of its parts. For example, if you are the only one wearing a mask and an infected person has breathed out some virus-laden aerosol, your mask would block 50%. But if the whole community are wearing masks, even the sick people generating the aerosol, then they would leave 17% less aerosol and hence the overall reduction in exposure is multiplicative — ~ 60%.

6. Public can be educated: For concerns around improper mask wearing and developing a false sense of security, they should be mitigated by public education. During times like this, transparency and mutual trust is important between authorities and the general public.

Finally, I would like to highlight two other points:

Infections and transmission dynamics are non-linear systems such as the concept of minimum infectious dose required to make a person sick and the reproduction rate. If your exposure to the virus is below a certain threshold — maybe even just a 50% difference, your body has more time to mount a defense while the virus replicates and can make the difference between getting sick or not. (More about “dose-response curve” in this New Yorker article). At a population level, the reproduction rate of 1.1 vs. 0.9 might only be ~20% difference, but is the difference between an exponential outbreak vs. an infection that will die down by itself over time.

Secondly, for those to point to Singapore as being a city-state that has successfully “contained” the outbreak so far without universal use of masks, please remember that Singapore is a population of 5.6 million people with a highly capable, respected, organized, science-led government (naming no names) and a population that is above average in terms of compliance. From day 1, Singapore has been on the ball with testing, with comprehensive contact tracing and isolation. Many countries around the world have already missed this boat by a long way. (EDIT: as of 3rd April, Singapore has also modified guidance to encourage use of reusable mask due to increased risk of community spread. Gov was not able to contact trace for 50% of infected persons — implying that virus is no longer contained).

Take action now - Some resources for making your own mask

What’s really cool is that many around the world have already taken the initiative to create homemade masks. In particular, an organization called HK Mask (led by a retired lecturer who has a doctorate in Chemistry from Chinese University of Hong Kong) has provided some test data to suggest that tissue paper inserts into cloth masks can substantially improve efficacy. He also offers up a range of patterns for different face sizes from kids to adults for free download.

While the science is not bullet-proof , rarely in life do we get to make decisions where there is zero risk of being wrong. In this case, being wrong means we suffered some unnecessary discomfort, wasted some time and cloth, being right means we saved lives.

Image Source: Business Insider

Don’t just take my word for it, listen to what these epidemiologists, public health experts and air quality experts say about the topic:

…there is an essential distinction between absence of evidence and evidence of absence. Evidence that face masks can provide effective protection against respiratory infections in the community is scarce, as acknowledged in recommendations from the UK and Germany. However, face masks are widely used by medical workers as part of droplet precautions when caring for patients with respiratory infections. It would be reasonable to suggest vulnerable individuals avoid crowded areas and use surgical face masks rationally when exposed to high-risk areas. As evidence suggests COVID-19 could be transmitted before symptom onset, community transmission might be reduced if everyone, including people who have been infected but are asymptomatic and contagious, wear face masks.

The contrast between face mask use as hygienic practice (ie, in many Asian countries) or as something only people who are unwell do (ie, in European and North American countries) has induced stigmatisation and racial aggravations, for which further public education is needed. One advantage of universal use of face masks is that it prevents discrimination of individuals who wear masks when unwell because everybody is wearing a mask

— From “Rational use of face masks in the COVID-19 pandemic” published in The Lancet, 20th March by:

• Shuo Feng: Epidemiologist at Oxford Vaccine Group, University of Oxford
• Chen Shen: Department of Epidemiology and Biostatistics, Imperial College London
• Nan Xia: PhD Candidate, School of Public Health, Li Ka Shing Faculty of Medicine
• Wei Song: Department of Economics and Related Studies, University of York
• Mengzhen Fan: Department of Chemistry, University of Oxford, Oxford, UK
• Benjamin J Cowling: Professor and Division Head of Epidemiology and Biostatistics, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong

The non-specific symptoms at early stages of COVID-19 and absence of clear transmission links have defied conventional containment strategy by case isolation and contact quarantine. So far, only compulsory social distancing, coupled with mass masking, appears to be successful, at least temporarily, in China

… absence of evidence of effectiveness should not be equated to evidence of ineffectiveness, especially when facing a novel situation with limited alternative options.

… Furthermore, transmission from asymptomatic infected individuals has been documented for COVID-19, and viral load is particularly high at early disease stage.4,5

… People wear masks to protect themselves in close person-to-person contacts, but unintentionally, they are protecting each other through source control.

… Cloth masks were used by surgeons successfully during operations before disposable masks were available.

From “Mass masking in the COVID-19 epidemic: people need guidance” published in The Lancet, 3rd March by:

• Chi Chiu Leung: Hong Kong Tuberculosis, Chest and Heart Diseases Association, Hong Kong, China
• Tai Hing Lam: School of Public Health. The University of Hong Kong, Hong Kong, China
• Kar Keung Cheng: Institute of Applied Health Research, University of Birmingham, Birmingham, UK

… With the increasing number of no-symptom patients, wearing a facial mask becomes more crucial, even under the current recommendations of US CDC, as everyone could be a potential unknown virus source. Before these people could be fully identified and quarantined as done by China, encouraging the use of facial mask is the most effective approach to avoiding further outbreak of the disease.

… Another concern about using facial masks is that people may tend to touch faces more often with a mask than without a mask. General test reveals face-touching is a spontaneous human behavior which can hardly be controlled (an average test showed at least 1–2 touches within 3 minutes if not purposely controlled). Wearing facial masks will reduce the risk of directly touching the mouth and nose — the most critical parts on the face.

… Besides actively producing various medical supplies, home-made facial masks were promoted creatively and shared in the society.

… Overall, it is not a reasonable and responsible practice to discourage the use of facial mask based on the resource availability.

… Last but not least, encouraging the wide use of facial masks in critical spaces regardless of people’s health conditions can provide significant social and psychological benefits. This will increase the public awareness of the severeness of COVID-19 and constantly remind people of the necessity of social distance. It will fully eliminate the biases towards those who are in infection and who are at risk; and will surely mitigate the growing hatred and violence towards those who are from the infection zones.

From “Facial mask: A necessity to beat COVID-19” published in Building and Environment, 23rd March by:

• John Zhai: Professor of Building Systems Engineering, University of Colorado at Boulder, USA, an air-quality and ventilation expert

The mainstream media are also starting to report on the topic, here are some relevant articles:

• Science Magazine — 28th March: Would everyone wearing face masks help us slow the pandemic?

“Despite messages from some health officials to the contrary, it’s likely that a mask can help protect a healthy wearer from infection, says Benjamin Cowling, an epidemiologist at the University of Hong Kong. Both surgical masks and the more protective N95 respirators have been shown to prevent various respiratory infections in health care workers; there’s been some debate about which of the two is appropriate for different kinds of respiratory infection patient care. “It doesn’t make sense to imagine that … surgical masks are really important for health care workers but then not useful at all for the general public,” Cowling says.

Masks might work better at preventing infection in hospitals than in public, he says, in part because health care workers receive training on how to wear them and because they take other important safety measures such as thorough hand-washing. “I think the average person, if they were taught how to wear a mask properly … would have some protection against infection in the community.”

• New York Times, 27th March - “More Americans Should Probably Wear Masks for Protection”

In many Asian countries, everyone is encouraged to wear masks, and the approach is about crowd psychology and protection. If everyone wears a mask, individuals protect each other, reducing overall community transmission. The sick automatically have one on and are also more likely to adhere to keeping their mask on because the stigma of wearing one is removed.

• Time Magazine, 4th March - “Health Experts Are Telling Healthy People Not to Wear Face Masks for Coronavirus. So Why Are So Many Doing It?”