All but two COVID-19 cases at a shuttered Etobicoke secondary school appear to have resulted from student-to-student transmission and it is possible that some were contracted during school events, Toronto’s top doctor says.

All 773 students at Silverthorn Collegiate Institute near Bunhamthorpe Road and Mill Road have been switched to online learning after Toronto Public Health declared an outbreak at the school on Monday evening.

During a briefing at Toronto City Hall on Tuesday, Chief Medical Officer of Health Dr. Eileen de Villa revealed that at least nine of the 11 student cases identified at the school so far appear to be the result of student-to-student transmission.

She said that officials are also looking into whether some of the infections could have been acquired during school events.

“I don't have all the specifics around all the different events but I do know that there were a number of different multi-grade activities and events both inside and outside of school that were found in the course of investigation that certainly represented opportunities for transmission,” she said.

Ontario health officials have repeatedly insisted that transmission within schools has been “minimal,” even as the province has regularly reported more than 100 new school-related cases of COVID-19 each day.

But the situation at Silverthorn Collegiate Institute could serve as a cautionary tale, given that transmission within the school environment appears to have played a role in the quick rise in cases.

Speaking with reporters on Tuesday, de Villa acknowledged that the Markland Woods community that the school is located in has a lower vaccination rate than the general population - 73 per cent of those 12 and up have been fully vaccinated versus 81.6 per cent city-wide.

For that reason, she said that Toronto Public Health has recommended that a mobile vaccination clinic be established at the school “to try to bring that rate up.”

She said that take-home COVID-19 tests are also available to be picked up from in front of the school today.

There is, however, still no timeline for how long the school will be closed for in-person learning.

The Toronto District School Board says that seven of the11 cases identified at Silverthorn so far are still active.

“These kinds of investigations do take time but I can assure you that all the measures have been put into place and we are looking forward to trying to get these kids back to school as soon as possible,” de Villa said.

Active cases continue to decline

The closure of Silverthorn Collegiate Institute, one of six in Ontarion on Tuesday, comes despite a steady decline in the number of active COVID-19 cases associated with the public school system.

The Ministry of Education says that there were another 117 new cases confirmed over a 24-hour period ending on Friday afternoon. That is down from 146 cases over the same time period last week and the 173 cases reported for the same time period two weeks ago.

The number of active cases associated with Ontario’s public schools is now down to 1,234. That number had went as high as 1,637 as of last Monday but has been trending down in recent days and is now the lowest it has been since Sept. 23.

However, Ontario’s public schools continue to see higher numbers of COVID-19 infections than they were seeing at this point in the 2020/2021 school year when the second wave of the pandemic was just beginning.

Back then it took until November 11 for the total number of lab-confirmed infections to exceed 3,000 but with the latest data Ontario schools have now reported a total of 3,088 lab-confirmed infections, including 2,713 among students. .

Addressing the outbreak at Silverthorn during a press’s conference earlier on Tuesday, Education Minister Stephen Lecce said that he continues to have faith in the precautions being employed in schools for the most part.

“This is a first in Toronto but I will note that Toronto Public Health, the chief medical officer of health, all of whom have have said the cautious preventative layers of protection put in place in our schools have been effective at reducing spread reducing outbreaks and keeping kids safe,” he said. “Three out of four schools in this province amid the Delta-driven fourth wave have no active cases at all but we are taking nothing for granted.”

There are currently 657 Ontario schools with at least one active case of COVID-19 but that number is down from a high of 819 schools at one point last week.

The number of active cases associated with the school system is also beginning to decline as a share of Ontario’s overall case count.

As of today, more than 28 per cent of Ontario’s active cases are associated with the public school system. But this time last week schools accounted for an entire third of Ontario’s active cases.

Of course, the impact on learning cannot be judged entirely through case counts.

According to a review of the data publicly posted by the boards on Tuesday, there are currently at least 230 individual cohorts self isolating in the Greater Toronto and Hamilton Area following a positive case in the classroom.