Transmission trouble: Statistician concerned over back-to-school plan

·3 min read

A high school science teacher who contributed to SickKids's recommendations on allowing children to return to the classroom this fall says that Ontario's back-to-school plan is unnecessarily risky.

There is nothing that can "compare the risk of returning to school with any risk that we have right now," Ryan Imgrund told CBC from his home in York region, pointing out there are more precautions around going to bars than to class.

Imgrund told CBC that the province missed a major opportunity to "mitigate risk" that will come with sending children back to school, especially in elementary grades where the Ontario government has not cut the size of classes.

He pointed out that most of Ontario's public health unit areas — including Ottawa's — have mandated masking and physical distancing in public spaces. But in many of the province's typical classrooms, it won't be possible for children to keep two metres apart.

And for students in Grade 3 and under, who won't be required to wear masks, it's even more worrisome.

"I don't know how it would be safer sending students back to school, than it would be going to a bar, or going to a gym," said Imgrund, pointing out that the rules for schools are more lax than for many other scenarios.

5% chance of infected person in class of 30

Using his background in science and research experience garnered at the Public Health Agency of Canada, Imgrund began tweeting out his graphs forecasting when Ontario infections would peak, and the likelihood of encountering a COVID-19 case in a crowd of a given size.

Those tweets attracted attention, including from the Southlake Regional Health Centre in Newmarket, Ont., which brought Imgrund in to devise statistical analysis on COVID-19 in March.

He also consulted on the report from children's medical experts released earlier this week, and the report report thanked him for his "valuable input."

His work focuses largely on the reproduction rate — the number of people one infected person is expected to infect. It changes over time and is dependent on our own behaviour, like physical distancing and wearing face coverings.

Without any safety precautions, every infected person with the novel coronavirus could spread it to up to four other people. Using local data and information, Imgrund pegged Ottawa's reproduction rate at .93 Friday, meaning that 100 infected people could potentially infect another 93 secondary infections.

Ryan Imgrund/Twitter
Ryan Imgrund/Twitter

Imgrund's work puts the risks of catching the virus in black and white.

On Friday, he published tables showing the likelihood of at least one student transmitting COVID-19 given cohorts of differing sizes.

He's crunched the numbers and said Friday that, at that very moment in Ottawa, in a classroom with 30 people, there'd be a 5.2 per cent chance at least one person would be able to transmit the virus.

For Sarah Arnold, the chances of transmission at school seems too high.

"It's too dangerous and I don't want to risk it," said the Barrhaven mother of three boys.

Submitted
Submitted

She said she worries what an infection would be do for an elderly or sick parent at home, infected by school-aged children.

"I'm afraid it would kill them," she said.

Tara Traves said she was initially relieved to hear that schools would be re-opening in the fall, but is less confident now due to what she called a "wishy-washy" plan that, she said, gives younger children too little credit for their willingness to wear masks.

"They can adapt," she said, adding the plan was a wasted opportunity.

"This is a long game we're in. The kids can't miss school [until] there's herd immunity."