School COVID-19 cases have mostly reflected the state of community transmission in the two months since they reopened, data and a new Canadian study show, but the latest numbers indicate signs of trouble in the country’s hardest-hit province, Quebec.
For most of the past two months, data for Ontario and Quebec compiled by The Globe and Mail and a separate Simon Fraser University study show the school share of COVID-19 cases has remained relatively consistent.
The problem, experts say, is the pandemic caseload in the community is persistently high in Ontario, even worse in Quebec and growing quickly in Western provinces, increasing exposure for students and staff.
In Quebec, where classrooms opened earliest, at the end of August, schools accounted for 20 per cent of the province’s COVID-19 cases for the first time last week after rising from 16 to 18 per cent in the previous three weeks. Students and school staff account for about 18 per cent of Quebec’s population.
Additionally, while Quebec has been in a plateau of new weekly cases since September, new school cases rose to 1,356 last week after three weeks around 1,250. The new cases and school share of coronavirus infections increased despite the government’s move to increasing online learning and mandatory mask use for high-school students earlier in October.
Montreal reported 93 active school outbreaks with multiple cases by the end of last week, up from 73 one week earlier. “It’s really in the school setting that we are seeing the greatest increase in the number of cases and the number of outbreaks,” said Mylène Drouin, the provincial director of public health for the Montreal region.
In Ontario, schools opened two weeks later and have remained more constant, with 7 to 9 per cent of overall cases over the past six weeks. Last week they accounted for 465 new cases, or about 7 per cent of overall cases, down 20 cases from the previous week.
A group of Quebec experts recently wrote an open letter calling on the provincial government to do more to improve air purification and ventilation in schools as winter sets in. Often the solution is as simple as opening windows and turning up the heat, they wrote. “Now is not the time to worry about saving money on energy,” the letter said, adding that schools with windows that don’t open need portable air purifiers.
In a recent research paper, Caroline Colijn, a professor at Simon Fraser University who specializes in mathematics and epidemiology, found schools are not amplifying infections but still need to take additional steps to reduce them.
“We don’t think schools are a huge driver. We looked at growth rates in secondary and primary schools in Quebec and they are not different in schools than the general community,” Dr. Colijn said. “But that doesn’t make it right. There are things that could be done differently.”
She said it’s important to get a handle on community spread to reduce exposure coming out of and going into schools. Her paper also recommends two school-specific measures to reduce risk: rapid, regular monitoring through tests, and classroom environmental controls such as better ventilation to reduce the size of clusters.
Kirsten Fiest, an epidemiologist at the University of Calgary, also emphasized the need for top-notch school testing and contact tracing. “In order to keep people working, there needs to be a priority on minimizing school-related spread and outbreaks,” she said. “Women will be most affected by children being out of school, as they have been throughout this pandemic.”
British Columbia, the best performer among Canada’s three biggest provinces for limiting coronavirus spread, had its first school outbreak in late October. “We are not seeing return to school causing amplification in our communities, but it does, as we expected, reflect what’s going on in our communities,” B.C. Provincial Health Officer Dr. Bonnie Henry said. “We need to focus our attention on the community to keep our schools open.”
The large gaps in school COVID-19 prevalence among B.C., Ontario and Quebec may illustrate the effectiveness of mitigation steps such as masks and online learning, but experts warn many other variables can also change the data, such as testing criteria.
Quebec has by far the highest community prevalence, the highest proportion of virus in schools, and only students in the final three years of high school are required to mask and take half-time online learning. There is no online option for other ages. British Columbia has even fewer restrictions. Ontario imposes masks and offers online learning for all ages.
“Generally, I think the approach to school openings were done better in Ontario than in Quebec,” said Gerald Evans, the chair of infectious diseases at Queen’s University. “But several confounders may account for differences, including community prevalence of circulating COVID-19, testing strategies, school precautions, etc.”
David Fisman, a professor of epidemiology at the University of Toronto’s Dalla Lana School of Public Health, has been calling for better school measures such as ventilation and reduced class sizes since back-to-the-classroom planning started. He warned it is difficult to be certain about virus prevalence in Ontario schools because the testing regime has been erratic. He pointed out the province had an 80-per-cent drop in testing for young children in mid-October after the system was overwhelmed and the province tightened testing criteria.
Caroline Quach, an epidemiologist and specialist in pediatric infectious diseases at the Université de Montréal, emphasized children should attend school as much as possible for education, special programs and socialization. “Having fewer children in classrooms might drive down transmission, but one has to look at unintended consequences,” she said. “It’s a matter of balancing out risks and benefits of each decision.”
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