COVID-19 numbers dip at city schools
But a number of caveats offset statistics' picture of reduced risk
The number of students and staff with confirmed cases of COVID-19 weekly at Ottawa elementary and secondary schools dropped in October, statistics from Ottawa Public Health show.
OPH data made public by the Ottawa-Carleton District School board provide an overview of cases at Ottawa's four school boards since students returned this fall through the end of October. The trend shows total COVID-19 cases at schools rising to 115 a week in early October, then gradually declining to 81 a week by the end of that month.
It provides insight into the risk COVID-19 presents to students and staff at schools. In total, there were 586 confirmed cases of COVID-19 at Ottawa's four school boards through the end of October.
It's difficult to draw sweeping conclusions, however, given all the caveats associated with interpreting the statistics.
For example, the number of lab-confirmed cases of COVID-19 at schools fluctuates based on how many people are tested.
Critics say it's reasonable to assume fewer infections are being detected at schools since the province relaxed self-screening rules on Oct. 1.
Before that, children with minor symptoms like sniffles were not allowed at school until they tested negative for COVID-19 or waited 14 days.
When the screening rule changed, the number of children tested plummeted, declining by 80 per cent in two weeks in the middle of October, according to Dr. David Fisman, a University of Toronto epidemiologist who posted the information on Twitter.
Children can have COVID-19 with no symptoms or only mild ones. There is no general testing of students at schools to estimate how many of them have the virus.
In meetings this week, trustees at Ottawa's two English-language school boards were presented with a variety of statistics and reassurances by staff that schools were doing well during the pandemic's second wave.
At the Ottawa Catholic School Board on Tuesday, a staff member said only 0.03 per cent of students had active cases of COVID-19 and only 0.3 per cent of students had contracted the virus since classes began.
That's significant, she said. “Those are remarkable numbers.”
The calculations were based on the board's total enrolment. However, about one-quarter of students aren't in school because they have chosen to study online at home.
And while the numbers appear tiny, the proportions are similar to overall Ottawa numbers that have made the city a COVID-19 hot spot.
Consider: on Thursday, Ottawa reported 495 active cases of COVID-19. In a population of one million, that represented .0495 per cent of the population.
Ontario's colour-coded reopening guide puts Ottawa in the orange or “restrict” zone. That is based on various indicators, including the weekly incidence rate of COVID-19 and the percentage of tests that are positive.
The trends at Ottawa schools reflect the overall trajectory of COVID-19 in the city, too. The average number of cases weekly in Ottawa peaked in early October, then gradually declined.
At the Ottawa-Carleton District School Board, staff noted that, while it had more COVID-19 cases at the end of October than the other three boards, it also had a much higher enrolment: about 74,600 students compared to 45,800 at the Ottawa Catholic School Board, about 26,000 at the French Catholic board, and about 17,500 at the French public board.
Another chart in the Ottawa-Carleton District School Board report showed the number of COVID-19 cases at schools related to outbreaks also peaked in early October, then declined.
Outbreaks are one indicator of whether students and staff are catching the virus at school.
The term “outbreak” can scare people, said Mary Donaghy, associate director of education at the Ottawa Catholic School Board, but she told trustees the most important indicators were how many cases were at schools and what was being done to contain them.
Ottawa Public Health declares an outbreak if at least two people at a school test positive for the virus within 14 days with an epidemiological link and there is reasonable evidence to suggest one of them contracted it at school.
An outbreak can be declared at a school with only two cases of COVID-19, while another school with multiple cases may not be designated as having an outbreak.
Donaghy said board officials were also aware of cases in which students in the same class or cohort also played together after school on sports teams.
But if there is a reasonable chance the virus was contracted at school, an outbreak is declared there, she said.
Ottawa Public Health says outbreaks are not generally “double counted” if, for example, two students with COVID-19 are in the same school class and also play on the same sports team, but there is no evidence of transmission to others.
“Through the public health and contact tracing investigation, the outbreak is determined based on the most likely transmission exposure,” OPH said in a statement.
However, it's possible for people to be part of two or more outbreaks, especially if they were infectious and spread the virus to several settings, the statement added.