This is an excerpt from Second Opinion, a weekly roundup of health and medical science news emailed to subscribers every Saturday morning. If you haven’t subscribed yet, you can do that by clicking here.
The rapid spread of more contagious coronavirus variants across Canada is driving a devastating third wave in much of the country and increasing the level of risk in situations previously thought to be relatively safe from COVID-19.
Experts say the risk of exposure is higher in everyday situations and the margin of error is lower for what we can and can’t do safely until more Canadians are vaccinated.
“The things that you’ve gotten away with previously, and that you’ve put into your mindset that were safe … it wasn’t that they were safe, it’s that you got lucky,” said Erin Bromage, a biology professor and immunologist at the University of Massachusetts Dartmouth who studies infectious diseases.
“That luck — it’s like rolling dice.”
Bromage said activities such as visiting a loved one, sharing a meal or working out in a gym might seem safe because public health restrictions may allow them, but are even riskier now than they were before.
The variants of concern not only appear to be more transmissible and potentially more deadly, but Bromage says they may also transmit for longer periods of time in infected individuals and bind to our cells more easily — providing more opportunities for infected people to spread the virus.
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“If you’re only transmitting for a few days out of an infection cycle, you can only have so many contacts during those days,” he said. “But if that duration of shedding is now twice as long, you can have double the contacts and so therefore it moves more easily between people.”
Linsey Marr, one of the top aerosol scientists in the world and an expert on the airborne transmission of viruses at Virginia Tech, says it’s possible variants may also be causing more virus particles in the exhaled air of infected individuals for longer.
“The virus is still transmitting the same way,” she said. “What’s different is likely that either the people who are infected are releasing more virus over a longer period of time or it’s possible that it takes fewer of those viruses to make you sick.”
The number of confirmed variant cases in Canada has skyrocketed in recent weeks, rising from about 2,000 a month ago to close to 17,000 this week and counting, with more than 90 per cent of those being the B117 variant first identified in the United Kingdom.
The P1 variant first discovered in Brazil is also on the rise in Canada, with cases doubling in the past week to more than 1,000 — mostly in British Columbia, Ontario and Alberta.
And the B1351 variant first found in South Africa is also picking up steam, with more than 150 cases identified in Quebec, more than 70 in Ontario and more than 50 in B.C. as of Thursday.
“The race between the vaccine and the variants is at a critical point,” Dr. Theresa Tam, Canada’s chief public health officer, told reporters Friday. “It is clear that we need stronger control to combat variants of concern that are driving rapid epidemic growth in many areas of the country.”
Tam said in a statement Thursday that serious illness can occur at any age and evidence indicates that variants of concern can be associated with more severe illness and increased risk of death.
Younger Canadians are being impacted harder in the third wave as well, Tam said, with infection rates highest among those aged 20 to 39 and a rise in the number of hospitalizations and ICU admissions in those under 60.
Airborne transmission driving spread
New research is shedding light on the way in which infection was occurring around the world even before variants took hold, calling into question whether our previous public health guidelines go far enough.
A recent study published by the U.S. Centers for Disease Control and Prevention showed that a singer at a church in Australia in July was able to infect several others from a distance of more than 15 metres indoors.
While a second CDC study found an infection occurred in a New Zealand quarantine hotel in September after an exposure time of less than a minute in an open doorway.
And a recent outbreak at a gym in Quebec City where physical distancing and mask use were not enforced has been linked to at least 440 cases of COVID-19 and one death in the community.
Quebec health officials say the rise of variants and a more relaxed approach to public health rules by residents have led to the spike in cases in the province, leading them to introduce a mandatory mask mandate for outdoor activities and indoor workplaces.
“The evidence just keeps piling up in favour of the importance of aerosol transmission,” said Marr. “We thought it was important before, I would say it’s probably predominant in terms of how the virus is transmitted.”
WATCH | Quebec City’s COVID-19 surge leads to more restrictions:
Bromage says the reluctance of Canadian public health officials to acknowledge aerosol transmission in a meaningful way has been “frustrating” and adds to confusion among Canadians about how infections are occurring.
Aerosol transmission refers to spread via microscopic airborne particles that can remain suspended in the air longer than larger droplets, which tend to fall to the ground within a distance of two metres — a trait that informed the original physical distancing guidelines.
“There has been a reluctance to accept that both in schools and in hospitals,” he said of aerosol transmission. “That poor messaging has led people indoors and infection starting up that really shouldn’t have.”
Canada revised its guidelines on how COVID-19 spreads to include the risk of aerosol transmission in November, weeks after other countries and international health organizations acknowledged the airborne threat.
“People tend to latch on to the first thing they hear, which was to wipe down your groceries a year ago,” said Marr. “But I think we need really a campaign to just clarify to people kind of how the virus is transmitting and then policies that match that.”
The CDC also updated its guidelines to say the risk of COVID-19 infection from surfaces is now officially considered low — meaning disinfecting groceries, wiping down packages and cordoning off playgrounds are likely unnecessary.
Outdoors not without risk
Experts say now more than ever, Canadians need to mitigate the increased risk of transmission from variants by going above and beyond public health guidelines and moving activities outdoors — though not all outdoor environments are created equal.
“Imagine, for example, the terrace of a cafe that would be enclosed by plastic sheeting on three of the four walls, in which you have a lot of people close to one another at tables,” said Dr. Raymond Tellier, an infectious diseases specialist and associate medical professor at McGill University. “This is logically outdoor, but physically has all the characteristics of an indoor environment.”
Dr. Amesh Adalja, an infectious disease physician and a senior scholar at the Johns Hopkins Center for Health Security in Baltimore, Md., says it’s important to remember that while transmission can occur outdoors, it’s much less likely.
“Even with the more contagious variants, the virus is still going to have difficulty transmitting in those settings,” he said.
“But when you look at some of the issues that we had in the United States, for example the protests after George Floyd’s death, those were all outdoors and we saw very little transmission.”
Even if you are moving activities outdoors, experts say to wear a mask with a high filtration level and stay as far apart from others as possible.
The fact is Canada’s third wave of COVID-19 is showing no signs of slowing down as the vaccine rollout gradually ramps up — meaning Canadians need to buckle down until more of us get a shot, experts say.
Bromage says both Canada and the U.S. have a “rough” couple of months ahead, but that Canada’s slower vaccine rollout means our third wave could last into June.
“The race is really on in the U.S.,” he said. “The variants are winning in Canada right now, whereas I think in the U.S. it’s sort of neck and neck.”
www.cbc.ca 2021-04-10 08:00:00