Canada is slowly reopening — and new research reveals where you’re most at risk of COVID-19

This is an excerpt from Second Opinion, a weekly roundup of eclectic and under-the-radar health and medical science news emailed to subscribers every Saturday morning. If you haven’t subscribed yet, you can do that by clicking here.


When 61 members of a choir gathered for a practice in Mount Vernon, Wash., on March 10 — including one with COVID-19 symptoms — the group had no way of knowing just how bad the situation could get.

The two-and-a-half-hour practice was an ideal scenario for the virus to spread: Choir members sat close to each other, sang together, shared snacks, and stacked chairs when it was over.

Two weeks later, 53 of the 61 choir members in attendance had either confirmed or probable cases of COVID-19. Three of those people were hospitalized. Two died.

Was it the singing, close contact, touching of surfaces, or sharing of food that caused the outbreak? Researchers aren’t sure which factors mattered most.

But one thing is common between that outbreak and others studied so far: Spending an extended period of time indoors together seems to help fuel the spread of COVID-19.

Watch: Are you safer from COVID-19 indoors or outdoors?

Andrew Chang asks an infectious disease doctor whether it’s safer to be indoors or outdoors during the coronavirus pandemic. 1:02

“There’s more and more evidence that it is capable of spreading through the air,” said Linsey Marr, an expert in the transmission of viruses by aerosol at Virginia Tech.

“The big outbreaks always involve crowded places, sometimes poorly ventilated, other times, we don’t know.” 

As provinces across Canada are slowly reopening, experts say emerging research offers lessons on how to do that safely — and it suggests tight, enclosed spaces may pose the biggest risk.

Where are outbreaks happening?

The choir practice is the subject of new research from the U.S. Centers for Disease Control and Prevention that shows how one close gathering can have devastating consequences.

The outbreak is known as what’s called a “superspreader event,” where a highly infectious person can spread the illness to many other people.

Two other recent reports from the CDC also found that the virus could more easily spread in an indoor setting with low ventilation over an extended period of time.

One looked at an outbreak at a call centre in South Korea. The report found 94 of 97 confirmed COVID-19 cases in an office building were all people who worked on the same floor.  

Another paper by researchers in China studied a restaurant in Guangzhou and found an infected individual without symptoms was apparently able to spread the virus to nine others.

The direction the air-conditioning system was blowing may have helped transport the virus particles to other diners, who otherwise had no contact with one another — while the report found those elsewhere in the restaurant who weren’t near the airflow didn’t get sick.

“Ventilation seems to play a role and what that means is that transmission is occurring via droplets in the air that people are inhaling or somehow picking up,” said Marr. 

“The fact that ventilation seems to matter strongly suggests that there is transmission happening through the air.”

The World Health Organization says airborne transmission of the virus “may be possible in specific circumstances,” such as the intubation of a patient in a hospital, but says there isn’t conclusive evidence it can spread from person to person through the air.

Friends are pictured in a public park near the seawall in Vancouver, B.C., on May 6. Emerging research shows simply talking loudly could generate droplets with the potential to carry the virus. (Ben Nelms/CBC)

Yet even the simple act of talking can produce hundreds of tiny droplets that have the potential to carry viruses and can remain in the air from eight to 14 minutes, a new study in the Proceedings of the National Academy of Sciences (PNAS) found. 

The research team didn’t study the speech droplets of people who had COVID-19 specifically, but they did conclude that even just one minute of loud talking could generate over 1,000 droplets with the potential to carry the virus.

“Protecting yourself from a droplet-borne infection is extremely complicated at the best of times,” said Dr. Andrew Morris, a professor in the department of medicine at the University of Toronto who studies infectious diseases.

“One of those things that’s been extremely consistent is that having people in close quarters — especially breaking bread, so to speak — has increased the likelihood of transmission.” 

Lessons for Canada about reopening

Against the backdrop of this growing body of research, officials across Canada are launching slow, phased reopenings that include many indoor settings.

Starting May 19 in Ontario, retail stores — but only outside of shopping malls, with street entrances — can start reopening with physical distancing measures in place.

In Quebec, the return to some semblance of normalcy is two-tier: Areas outside Montreal are reopening, but the provincial government has already twice delayed easing restrictions in and around the city itself — the epicentre of the province’s COVID-19 cases.

And in British Columbia, restaurants, hair salons, retail stores, museums, and libraries are all slated to reopen soon, though bans on gatherings of more than 50 people will remain in place and nightclubs and bars are expected to remain shuttered longer.

Regardless of when these types of businesses officially reopen across Canada, the research trends can help us navigate which activities put Canadians more at risk, said Jason Kindrachuk, an assistant professor of viral pathogenesis at the University of Manitoba. 

Kids socially distancing at a school for children of essential service workers in West Vancouver. Experts say indoor settings with poor ventilation are a growing concern for the spread of the disease. (Ben Nelms)

“It informs our decisions when we start to think about things like reducing [physical] distancing measures,” he said, adding that means anything from interacting in stores or dining at a restaurant. 

“We now have to think about new strategies to employ to be able to reduce these types of events.”

‘Move as many activities outdoors as possible’

Kindrachuk said examples like glass barriers for cashiers could become part of the “new normal” of society after the pandemic ends, and more people will think about how easily infectious diseases spread on a day-to-day basis. 

“I think we’ll be revisiting many of the aspects of our lives where people are in close quarters,” Morris said.

“I don’t think anyone can now imagine going on a subway system that’s totally jam-packed and feeling comfortable right now.”

A man waits on a subway platform in Vancouver on April 22. Experts say cramped settings like transit are another potentially risky environment. (Ben Nelms/CBC)

Morris said these types of social settings where people congregate en masse — like schools, malls, stadiums and transit — will be an ongoing concern for the spread of the disease.

“Now the only way that we’ll be able to safely manage this moving forward is by getting us to a very low level, and having ongoing surveillance, and accepting that — at times — people are going to be infecting others,” he said.

“But if we have very good surveillance and contact tracing, we will be able to limit the extent of the spread once it rears its head.” 

The simplest way to reduce transmission, according to Marr, is to reconfigure our lifestyles to avoid crowded indoor places, particularly those with poor ventilation.

While talking about gatherings this week, B.C. Provincial Health Officer Dr. Bonnie Henry put it this way: “Outside is always better than inside.”

Watch Dr. Bonnie Henry explain how to safely host a barbecue:

Dr. Bonnie Henry shares her recommendations on how to create physical distance while hosting a barbecue this summer. 1:24

It’s a move that should prove easier in the summer months when restaurants and bars, for instance, can potentially open patio seating.

“I think we should try to move as many activities outdoors as possible,” Marr said. “Obviously avoiding dense crowds is a good idea and paying careful attention to ventilation in buildings is going to be helpful.”

A closed patio space is seen in downtown Vancouver on Tuesday. Providing more space for people should prove easier in the summer months when restaurants and bars can potentially open patio seating. (Maggie MacPherson/CBC)

Reconfiguring society in that way could give people open-air options to resume a somewhat normal life, while reducing their risk of catching COVID-19.

“We can’t stop it,” Marr said, “but we can slow it.”


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