COVID-19 is different from any virus the world has encountered before because it is shed and communicated to others by infected persons who are either without symptoms or pre-symptomatic.
“A person infected with coronavirus — even one with no symptoms — may emit aerosols when they talk or breathe. Aerosols are infectious viral particles that can float or drift around in the air for up to three hours. Another person can breathe in these aerosols and become infected with the coronavirus. This is why everyone should cover their nose and mouth when they go out in public.”
In order to control the transmission, the current practice of social distancing appears to have only a limited success here in Canada. This is particularly true when you compare the success at controlling the curve in Asian countries. This is one site that shows trends, but the evidence is tremendous.
The western world has clearly not done sufficient testing, but the obvious difference between the countries that were affected and managed to control the rate of transmission and those who did not is wearing masks. So we need to wear masks, but who and why?
Research has shown that the initial point of infection is generally the upper respiratory tract. It has also been found that the coronavirus “quickly begins producing high viral loads, sheds efficiently, and grows well in the upper respiratory tract (nose, mouth, nasal cavity, and throat).”
Recent science has shown that “the major transmission mechanism is not via the fine aerosols but large droplets, and thus, warrant the wearing of surgical masks by everyone”. This text and the photo above were taken from this excellent scientific article:
Because the virus is shed efficiently from people with no symptoms, and because “breathing it in” is the main pathway of infection, this means that simply walking behind an apparently healthy person at the supermarket could cause you to breathe in sufficient amounts of virus to become infected.
The efficiency of a mask is two-fold and highly variable based on the type of mask. While most masks were designed to protect the wearer as PPE (Personal protective equipment) from harmful fumes or particles, surgical masks were designed to protect the patient from the doctors and nurse’s exhalation (source control). All masks will have a certain efficiency either way as source control or as PPE, though in some cases it may be very low.
By definition, an N95 mask will prevent 95% of particles of 0.3 micron as protection. These are best used to protect the wearer and are scarce on a world level and thus needed for health workers. It would be very difficult to provide these to the general public. These would likely be more than 99% effective at both protecting the wearer as well as protecting others from the harmful droplets which are suspected to be the main route of transmission (source control).
One detailed study using surgical masks concluded that : “Our findings indicate that surgical masks can efficaciously reduce the emission of influenza virus particles into the environment in respiratory droplets”
This suggests that a surgical mask would be over 90% efficient in preventing droplets with viable virus particles from being shed to the immediate environment by the wearer (source protection). It is unclear what the efficiency is to protect the wearer who is not infected, as PPE.
For example, let’s assume that the surgical mask is 90% effective as source protection and 50% effective as PPE. Assuming you’re walking (2 m) behind an infected person shedding virus while simply breathing in a grocery store. Assume you have a 20% chance of actually breathing sufficient virus through droplets left by this infected person, when neither wears a mask. If the other person is wearing a mask, this is reduced to 2%. If you are wearing a mask, this is reduced to 10%. If both are wearing masks, the risk is reduced to 1%.
Homemade cloth masks are highly variable as much depends on the material and the fit. These may still be up to 75% efficient as source control, or as low as 30%. As PPE, they may be less than 50% effective and maybe as low as 10% effective.
Using the above example for other mask efficiencies led to the construction of the table and graphics below. To simplify the calculation, we can assume a 100% chance of getting infected without a mask. The risk reduction would therefore be multiplied by the actual risk. For all examples, the combined source and personal risk is that of the same mask, except for the final example where a clinical situation is assumed, where the patient wears a surgical mask and the nurse (or doctor) wears an N95 mask. Note that the efficiencies of each of these masks are assumed as much information on these is contradictory and variable.
The data from the above table was put into graphical form for visualisation. This graph simply shows the assumed efficiencies of each type of mask. Note that the source protection efficiency directly represents the reduction in virus shedding onto surfaces. This means that in the supermarket example above, this is also the reduction in virus particles being deposited on surfaces, including produce.
This graph shows the combined effect assuming both parties wear the same mask, except for the last example, where the source protection is a surgical mask and personal protection is an N95.
You can’t see the bars for the first and last examples because they are so small. This next chart was prepared using a logarithmic scale and instead of percentages, the axis represents the number of infections that would occur per 100 hundred people that would have been infected without any protection.
The efficiencies here are assumed and do not represent actual science, as it is too early to actually know the size of typically transmitted droplets and the filtration efficiency of each of the different types of masks. Different surgical masks are likely to have different efficiencies and proper use and fit of the masks is also critical. Regardless, this conceptual exercise uses real math and definitely shows the potential effect of facial protection in the community.
Essentially, THIS IS HOW YOU FLATTEN THE CURVE. Even with a “good cloth mask” which only protects the wearer by 50%, you could have one tenth the number of transmissions. This could flatten the curve sufficiently that people could return to work and be productive, instead of at home stressed and collecting unemployment insurance. Without overloading the hospitals, the economy could take less of a hit and the kids could return to school if everyone had a good mask.
In the Real World
An excellent example of what to do is South Korea, who was hit hard and early in this pandemic. They flattened the curve and the main reason is that they ramped up production of masks and provide two masks per week to everyone.
Knowing the above, wouldn’t you, the reader, prefer to go to a grocery store where all employees wear masks all day long? Wouldn’t you prefer to shop in a location where every person entering must wear a mask? If they were available, the grocer could sell a mask to each person entering the store.
If people walking down the street were wearing masks, if delivery people all wore masks, if children wore masks, the transmission rate would decrease significantly. Sufficiently so that we could return to work – eat in our own personal spaces and wear a mask at all times not ingesting food or drinking.
In Taiwan, the schools were kept open through the use of masks and dividers for eating lunch. https://www.cbc.ca/news/business/taiwan-covid-19-lessons-1.5505031
Commerce is open in Taiwan and there is no rule to keep 2 m apart. But there are rules indicating that all must wear masks in public or potentially face a fine. Right near the source of the coronavirus, a small, densely populated island of 24 million, they only have 393 cases (April 13). We could also open schools and all businesses in Canada if we had the masks and the regulations.
In Canada, the extreme social distancing measures currently enforced are definitely having a certain positive impact, but these are not sustainable economically. It is not possible to return to normal life while maintaining 2 m distance. Board room meetings, kitchen workers, pharmacists behind the counter, buses, subways, taxis – all of these services cannot be efficiently completed while maintaining 2 m distance. Students cannot be in a classroom or in hallways and maintain that distance. Car-pooling is a great way to minimise our carbon dioxide emissions, but you cannot put four people in a car and maintain 2 m distance.
The Next Step
It is clear that if the general population had masks, life as we knew it could eventually return and would return much faster than without. The science has proven that masks are more effective than maintaining 2 m distance and that since that distance cannot be maintained, the only viable solution to a quick return to normal is to have masks for everyone.
Here in Canada, masks are not produced in any significant number. Most masks are produced in Asia. International competition for masks is at an unprecedented level right now and this is likely to continue for many months, if not years. Some are produced in the USA, but the federal administration is now trying to block exports of masks to Canada.
We need to identify any and all industries in Canada that can be converted to making masks. We need to fund the most applicable industries to source out the materials and manufacture the masks.
This investment will pay off in human lives and the Canadian economy, if not directly in profit. But the continued need for masks throughout the world, plus the desire for people to stock them at home, will likely make this a sustainable long-term venture as well.