Montrealers have waited anxiously for weeks looking for signs of the third COVID-19 wave, one that has washed over just about every other major Canadian city with a rapid increase in cases and serious illness.
Most public-health officials, including those in Montreal, are hesitant to declare any victory over COVID-19, but as the third wave has crested in Ontario, Alberta and much of Quebec, Montreal remains notable for having no third wave so far.
The city came out of the second wave from a high of 1,274 new cases on Jan. 7 to fewer than 200 new daily cases this week. Over that time, cases spiked in Vancouver, Calgary, Toronto, Ottawa and Quebec City, while Montreal remained in decline or on a plateau.
It’s not quite a miracle, but a mystery: How has Canada’s pandemic epicentre, the city with one-fifth of Canada’s 24,756 pandemic deaths, managed to put off a third coronavirus resurgence?
The explanations are multiple and include revamped contact tracing, public compliance, high levels of immunity from both targeted vaccination and previous infections, a curfew along with other strict measures and luck.
One of the most important factors setting Montreal apart was a decision by the city’s public-health unit led by Dr. Mylène Drouin to invest heavily in enhanced contact tracing to reach back and find superspreaders at the root of infections from variants of concern.
“In the second wave, when we had 1,200 cases, we really just did the essentials to make sure we got in touch with people, got them to isolate,” said Dr. David Kaiser, Chief Medical Officer at Montreal public health. “We didn’t have the capacity for more complex investigations. When we had a few hundred cases a day and started with literally two variant cases, we did.”
Montreal public heath doubled contact-tracing staff to 1,200 through the second wave, recruiting from the ranks of retired medical professionals and unemployed people in community groups and the cultural sector.
When cases started to subside in January, those tracers were kept on staff and were ready when community spread of variant cases began later that month.
“We had the people on the payroll and trained and ready to redeploy. We pivoted quickly and rewrote our process to be extremely aggressive with variant cases. We followed each chain of transmission with the variants to extinguish it,” Dr. Kaiser said.
Montreal employed an approach known as backward tracing, which came to public prominence in the fall but faded quickly in most of Canada as the virus overwhelmed resources.
The technique relies on the fact about 20 per cent of people infected by coronavirus are responsible for causing about 80 per cent of spread.
In Canada, even basic contact tracing has often collapsed when cases are too numerous. Public-health officials have mainly tried to do forward tracing, when they call immediate contacts of cases to prevent forward spread.
With backward tracing, investigators look back to find the person who infected the new patient, sometimes reaching multiple generations of infection until they find the superspreader person or event at the root.
Public-health officials can then track forward from the superspreader contact to test and isolate people with and without symptoms, slowing further transmission.
“The majority of people don’t generate new cases,” Dr. Kaiser said. “But if we can identify where people got their disease, we can identify those who do generate new cases and break the chain.”
As part of the rewritten playbook, public health officials treat a single variant case as an outbreak. While schools in Montreal have mostly remained open to in-person learning, public-health officials were quicker to send home classes or closed schools preventively.
In Montreal, the major concern was the B.1.1.7 variant, which was first identified in Britain. A stroke of laboratory fortune helped the tracking effort. When B.1.1.7 was first identified in Quebec in late December, the province’s labs did not have kits to systematically test for it.
With the original strain of COVID-19, laboratories confirmed cases by identifying three genes contained in samples. With the B.1.1.7 variants, staff at the laboratory at Montreal’s Shriners Hospitals for Children observed one of the three genes was missing.
After the observation was confirmed, Montreal public health started presuming test results containing the anomaly were the variant. They would immediately launched the aggressive variant tracing protocol instead of waiting for detailed confirmation through genetic sequencing at the provincial laboratory.
“It was a stroke of luck, really, that this was a tell-tale mutation that had huge importance for the trajectory of the pandemic,” said Dr. Raymond Tellier, a microbiologist at McGill University Health Centre. “What first appeared as a bug was a feature. We jumped on this and it bought us a month until we had variant test kits.”
Dr. Tellier said other labs in Canada and elsewhere spotted the same anomaly, but he credited Montreal public health for acting quickly on it with aggressive tracing.
Recognizing Montreal’s role as a pandemic hot spot, the provincial government sent more vaccine doses to the city when shipments started in winter. While the bulk went to vulnerable older populations, the city used some on homeless people and tried a pilot project to vaccinate parents in hot-spot neighbourhoods on the western side of the city.
Areas of Côte Saint-Luc and Côte-des-Neiges reached 50-per-cent vaccination levels in April when the rest of the city was still mostly under 30 per cent. The strategy slowed virus spread from neighbourhoods that had previous triggered Montreal waves.
“Part of our area was the hottest of hot spots weeks ago and they nipped it in the bud before it spread beyond,” said Lawrence Rosenberg, chief executive officer of the west-central Montreal health district.
In recent weeks, the strategy turned to grassroots efforts to bring up vaccination levels in poorer neighbourhoods.
Martine Thériault, one of 20 public-health community organizers working in Montreal’s south-central area stretching from Verdun through downtown to Plateau-Mont-Royal, described how her team has targeted seniors in low-income apartments, placed vaccine promotion material in food bank baskets and sent speaker-vans across neighbourhoods calling out vaccine reminders in a multilingual blitz.
The strategy has narrowed the vaccination gap, at least among older populations. March statistics for 60-year-old-plus Montrealers showed lower-income Verdun trailed Île-des-Soeurs, where residents are more well off, by 20 percentage points in vaccination rate. By late April, the gap was cut in half and the two areas were at 84-per-cent and 93-per-cent coverage, respectively.
Now, the challenge is to carry on closing the gap with younger age groups.
Marie St-Louis, co-ordinator of public-health outreach for south-central Montreal, said they are considering street performances to spread the word and mobile pop-up clinics in parks. “The beauty and challenge of this situation is we have no choice but to be flexible,” she said.
Dr. Drouin, the director of Montreal public health, declined to be interviewed for this story. Throughout Montreal’s pandemic lull, she has been reluctant to declare success, acutely aware that one missed superspreader event could undo it all. Everyone interviewed for this story added a caution similar to this one from Dr. Tellier: “Don’t jinx it.”
But in a recent press event, Dr. Drouin expressed happiness at how the strategy has played out. “It’s a fragile balance,” she said, “but I’m quite proud of the situation.”
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