Public health orders require simplicity, logic By: Dan Lett Posted: 7:00 PM CDT Monday, May. 3, 2021

Opinion

Hey there, time traveller!
This article was published 02/05/2021 (1236 days ago), so information in it may no longer be current.

It was splitting hairs. Or, more precisely, splitting droplets.

Dr. Brent Roussin, Manitoba’s chief public health officer, took time out of his daily COVID-19 briefing on Monday to once again remind Manitobans that larger viral droplets, and not smaller aerosolized emissions, pose the greatest risk of transmission.

Roussin’s clarification appears to have been prompted by new research published late last month in The Lancet, and a decision by the World Health Organization last week to tweak its guidelines based on the growing body of evidence showing airborne transmission of COVID-19 is a much larger threat than previously thought.

The re-think has been building for months now, ever since it became clear the sheer numbers of confirmed COVID-19 infections could not be explained solely by close-contact inhalation of larger viral droplets. Much smaller, aerosolized emissions — which travel farther from an infected person and hang in the air much longer than droplets — had to be playing a role.

This new thinking is starting to shake some of the principal assumptions we’ve made about transmission and public safety.

Just last week, the Massachusetts Institute of Technology published a new study that determined the six-foot (or two-metre as we like to say in Canada) social distancing guideline “does not provide sufficient protection” in indoor spaces because of airborne transmission. Masks, the study concludes, are the most important protective measure.

Just last week, the Massachusetts Institute of Technology published a new study that determined the six-foot (or two-metre as we like to say in Canada) social distancing guideline “does not provide sufficient protection” in indoor spaces because of airborne transmission. Masks, the study concludes, are the most important protective measure.

All of this emerging science makes Roussin’s decision to double down on what epidemiologists have started calling “the droplet dogma” particularly frustrating.

In the final analysis, it doesn’t really matter whether droplets or viral emissions pose the biggest threat.

Both are clearly a threat, and the good news is that if you impose measures to protect people from aerosolized viral emissions, you will also be protecting them from droplets. So, why not do both?

If you use that simple reality to guide public health orders, it means that while social distancing will continue to be important, it is not enough on its own. You have to do much more to ensure that people are protected from both droplets and aerosols, both indoors and out.

Roussin has done an excellent job of reminding Manitobans that outdoors does not equate to “zero risk.” In fact, it has been proven that when people interact maskless in close quarters with each other, even while outdoors, there is a tangible risk of infection.

Unfortunately, Manitoba’s public health rules do not seem to reflect that reality.

Manitoba currently has a mandatory indoor mask mandate, a ban on household interactions and a limit on capacity in public, indoor settings. But the rules still allow up to 10 people to gather maskless in an outdoor public setting and up to four people from different households to share a table on a restaurant or bar patio.

At this stage of the pandemic, with the knowledge we have about the virus and how it is transmitted, it is simply not acceptable to allow maskless people to interact anywhere, even outdoors.

But does that mean we have to wear masks all the time, indoors and out?

No, it does not.

At this stage of the pandemic, with the knowledge we have about the virus and how it is transmitted, it is simply not acceptable to allow maskless people to interact anywhere, even outdoors.

Linsey Marr, a professor of civil and environmental engineering at Virginia Tech and one of the world’s leading experts on viral transmission, has created the “2-out-of-3 Rule,” the clearest and most effective guideline to date on when masks should be used against the risk of infection.

Marr’s rule goes something like this: if you’re outdoors and physically distanced, you do not need a mask; if you’re outdoors but not physically distanced, wear a mask; if you’re indoors, regardless of whether you’re socially distanced or not, wear a mask.

There is a beautiful simplicity to Marr’s guidelines. In addition to helping people decide when they really need to wear a mask, the two-out-of-three rule could be used to assess the efficacy — and perhaps the sanity — of restrictions in public health orders.

Using Marr’s rule, we can see that outdoor public gatherings and patio table-sharing are really bad ideas. In both of those scenarios, unless steps are taken to remain physically distant from other people, there is an enhanced risk of transmission. And given the fact that no one can drink a pint through a mask, the patio action is totally ill-advised.

But here’s the rub; you could use Marr’s rule to restore certain interactions Manitoba is currently restricting.

For example, using the same rule, you could invite a small number of people into your backyard for a fire if you are physically distanced and if you continue wearing masks. According to these simple guidelines, that would be safer than mingling with nine other maskless people in a park.

Underlying the recent flood of research and advocacy around airborne transmission is a simple and elegant lesson: in a pandemic like this one, there is really no public value in ignoring or downplaying any one form of transmission.

If you protect people in situations where they might, just maybe, inhale a viral aerosol emission, you are definitely protecting them against inhaling a viral droplet.

Simplicity and logic. At this stage of the pandemic, those are the two qualities we have a right to expect from our political and public health officials.

Instead, we’re slicing droplets.

dan.lett@freepress.mb.ca

Dan Lett
Columnist

Born and raised in and around Toronto, Dan Lett came to Winnipeg in 1986, less than a year out of journalism school with a lifelong dream to be a newspaper reporter.

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