COVID19: Let’s Talk About Masks

by Raywat Deonandan, PhD
Epidemiologist & Associate Professor
University of Ottawa
(I add my credentials to these COVID-19 blog posts in case they get shared. I want readers to know that my opinion is supposedly an educated and informed one)

It’s been a while since I updated this blog. That’s what happens when you have a newborn at home: time just sort of slips away. That’s my official excuse. But the real reason is that I kept waffling on a topic. I was going write about what a second COVID-19 wave would look like, or an update on vaccine research, or a response to one of those endless streams of pseudo-science that keeps erupting from this emergency, or a response to that special set of contrarians who make interesting non-mainstream COVID points, or that long awaited analysis of the Swedish experiment. I just couldn’t choose.

But a question that I thought had been well settled and well understood kept being brought up in media interviews. So that’s what I will talk about today: why we should be embracing masks.


Wait, Weren’t You Eggheads Saying No To Masks?

Some experts were indeed hesitant to embrace basic cloth masks for the general public early in this epidemic. I’m on public record of having been noncommittal to the idea, as in this bit on UK television.  But I’m also on more recent record as being vocally supportive of masks, as in this article and this radio interview.

The problem is that infection control people were, early on, stuck in the clinical paradigm. They saw masks as something worn by doctors and nurses to protect themselves. In other words, masks were PPE (personal protective equipment). A more recent radio interview I did began with the host asking about whether her mask was being worn and removed “properly”, again situating its use well within the PPE world.

This was a mistake. The power of masks to control this epidemic is not in its use as PPE, but in its ability to marginally reduce transmission across a population. It’s a delicate distinction.

Doctors and nurses use masks –typically tightly fitted N95 respirators– to protect themselves against infection because they work in environments that are often saturated with pathogens. In this time of emergency, they almost never remove their masks lest they risk exposure. And they have learned mask discipline, meaning the careful methods of putting on, removing, and disposing of masks to prevent spreading infection from one place to another.

There’s a reason that doctors and nurses typically change their masks and gloves in between patients. Their PPE could spread infection from one person to another.

So with that experience, there was hesitation in recommending mask use among the general public. Most people don’t have the discipline to avoid touching their faces to adjust their masks. Most people could not be relied upon to remove their masks carefully and to avoid spreading potential infection from stores to their cars to their homes.

As a result, many experts were hesitant to recommend mask-wearing to non-clinicians. Masks are a technology, after all. And as with all technologies, proper usage must be learned lest more damage be wrought.


So What Changed?

A simple realization occurred. For the purposes of reducing community transmission of an infectious disease, masks are not PPE. Rather, masks are a simple tool, maybe even a fashion accessory, that can be used imperfectly by non-experts to incrementally reduce community transmission of this disease.

You don’t need clinically rated high tech respirators. And you don’t need perfect infection control behaviours with respect to handling your mask. You just need to wear a piece of cloth over your mouth and nose when you can. That’s it.

Repeat after me: my mask protects you, and your mask protects me.

When the incident cases in the population are few, as they are now in Canada, the probability of encountering the disease is very low. The risk now is that pre- or asymptomatic people will spread the disease without knowing it, and kick off new outbreaks.

So a mask is a tool for reducing the probability of an infected person –especially a non-symptomatic person– from infecting others. It’s not PPE.


How Does It Work?

An N95 respirator has something like a 3-micron fibre width, which means that few viruses can get past it. But a homemade cloth mask as a much wider fibre width, so all kinds of things can get through.

What’s the point of that?

Once we’re out of the PPE way of thinking, all a mask does is slow down the flow of air from your mouth. It’s a wind break.  Even a flimsy piece of poor cloth over your mouth will prevent the air from your lungs from going more than a few centimetres past your face. And that’s all it takes to slow the transmission of respiratory droplets.

Wearing one of these things yourself will offer some minimal protection. But it affords a great amount of protection for other people if it turns out that you’re infected and you don’t know it. You’ve probably seen some version of the following image, which seeks to get that simple message across:


So let me say that again, in case you missed it. Wearing a mask prevents infected people from spreading their infection to others. Don’t focus on using it for self-protection. It’s for the protection of the community. This is the subtle change in thinking that got most public health experts onboard the mask train.

If you doubt that a mask prevents outward transmission, consider this little visual experiment by medical lab tech Katie Corley, who coughed on two petri dishes, one while wearing a mask, and one without a mask:

Her very brief description of her experiment is worth a read, especially for her deliciously sarcastic tone.

I’ve seen some argue on social media that since the virus is so small, it will go right through the mask and not protect anyone. Ms Corley’s experiment above clearly dispels that assumption. But the science is this: viruses are suspended in respiratory droplets that are quite large. Many droplets will indeed be stopped by your homemade cloth masks. Many more will be slowed by the reduced air velocity caused by the mask. Bottom line: fewer people will become infected.


How Do You Know It Will Work At A Population Level?

Many studies are now making it to print that show that if enough people wear face coverings, the rate of spread of this disease can be curtailed substantially. This study from the German Institute of Labor Economics estimates that spread can be reduced by 40% with sufficient mask-usage.

This study comparing different countries’ responses found that countries that adopted masks within their first month of their outbreak had profoundly better outcomes, as per this graph:

As Dr Jennifer Kwan put it (sarcastically), “It’s almost like a virus that transmits through your mouth & nose, could be better controlled with something that covers your mouth and nose.”

A pre-print study out of Cornell University suggests that if 70% of the general public wear masks and contact tracing is conducted at 60% efficiency (i.e., within a 4-day time frame upon a positive test), the epidemic curve can be quickly flattened in the hardest hit countries.

At the start of this pandemic, most of the studies available to public health experts concerned the use of masks by clinical staff for self-protection. It’s therefore not surprising that they were unprepared to recommend it to the masses. But that has changed.

As per this study,  “We recommend the adoption of public cloth mask wearing, as an effective form of source control for now, in conjunction with existing hygiene, distancing, and contact tracing strategies.”


It’s Worked Before

I was recently reading this 2007 article about lessons learned from the SARS epidemic almost 2 decades ago. The paper’s three big findings relevant to our current pandemic were: (1) transparency is key; (2) 19th century technology is still very effective; and (3) animal husbandry is bad for human health.

Now, we can debate many aspects of those conclusions. But I draw your attention to the second, that things that worked in the 19th century still work today. Physical distancing, washing your hands, not touching your face, staying home when you can —these are the age-old, tried and true methods of combating a raging infectious respiratory infection that were put to fine use 100-200 years ago.

As sociologist Zeynep Tufekci wrote, mask use “has always been advised as part of the standard response to being around infected people.” Just look at this now famous image of a football game from 1918 during the Spanish flu pandemic:

They did it then. We can do it now.


What Are The Risks?

For most people, there are no appreciable risks in wearing a cloth mask when you go out on your errands. You will read nonsense about bacteria multiplying in the wetness of the mask, or people getting ill from re-breathing their own carbon dioxide. Do you really think the legions of doctors and nurses who wear thick and dense N95 masks for hours a day suffer these effects? Of course not. It’s nonsense.

Just wear your mask when you go out, take it off when you’re at home or alone, and wash it every day.

The real danger is the false sense of security that a mask might offer some people. Wearing one might also cause some people to touch their face more often than usual. Some degree of mask-wearing discipline needs to be cultivated.

As well, there is something to be said for asthmatic, claustrophobic, and autistic people. For them, mask wearing can be challenging. And the hard-of-hearing often need to communicate by reading lips. So masks might not be a good solution for everyone. But they just need to be for most people.


The Bottom Line

It’s true that the cloth masks worn by non-clinicians are not useful in helping you, an individual, avoid catching the coronavirus. But that totally misses the point. If enough people wear masks, they can be extremely effective slowing, or even negating, the population spread of this disease.

So if you can’t physically distance and must be around people, please wear a mask that covers your nose and mouth. You probably don’t have the disease. But you might. So please don’t be part of the problem.

As Jeremy Howard writes, “Until a vaccine or a cure for COVID-19 is discovered, cloth face masks might be the most important tool we currently have to fight the pandemic.”

But while important, a mask is only one (imperfect) tool. In and of itself, a mask cannot stop this pandemic. But when combined with physical distancing, frequent hand-washing, avoiding face-touching, and eschewing large indoor gatherings, masks can help to drive the population indicators of this disease downward and help to keep us all safe.