As COVID-19 case counts tick upwards in Manitoba schools, public health officials continue to downplay the importance of systematic testing in one of the province's most widely dispersed at-risk populations.

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As COVID-19 case counts tick upwards in Manitoba schools, public health officials continue to downplay the importance of systematic testing in one of the province's most widely dispersed at-risk populations.

Manitoba's testing protocol and its associated costs remain the biggest barriers to implementing widespread screening in schools.

Processing one COVID-19 test through Cadham Provincial Laboratory is estimated to cost approximately $30, not including the cost of swab collection at the test site.

With approximately 224,000 students, teachers and school staff, a full round of "census sampling" would require exclusive use of testing capacity for up to 100 days and cost an estimated $6.6 million.

But an epidemiologst at McGill University told the Free Press Friday there is a far less-expensive and more effective alternative.

To avoid the spectre of rolling school closures, Dr. Dick Menzies, director of McGill's respiratory epidemiology unit, is calling for a seismic shift in testing, proposing the use of mobile teams and in order to detect asymptomatic carriers to isolate them before infections spread.

Children and school staff are — along with contacts of positive cases, hospital employees, community health-care workers and essential business employees — among the highest-priority at-risk groups Menzies has identified.

Other than contacts of positive cases, the other groups regularly congregate, a factor allowing mobile teams to conduct screening of large random samples.

Called "surveillance sampling," where 10 per cent of a population is tested, the approach allows for earlier case identification and public health response.

At the moment, if an outbreak occurs, entire cohorts of students are rapidly transitioned to online learning. That's what happened this week at Winnipeg's John Pritchard School. An outbreak of seven cases, and suspected transmission within the school, sent 250 students home for at least one 14-day incubation period that started Wednesday.

While high school students are permitted to learn online from home without parental supervision, the same isn't true for children under age 12; John Pritchard's classes range from kindergarten to Grade 8.

The situation creates significant challenges for some households with working parents, many of whom were suddenly scrambling to make arrangements with employers after being advised of the situation Tuesday evening.

In some cases, employers are able to make accommodations, but others might have to replace staff. Small businesses unable to turn on a dime could face temporary or permanent closure.

In short, Manitoba families and educators are looking at a situation with an uncomfortably high degree of uncertainty, and if the John Pritchard School outbreak is a sign of things to come, there could be significant economic repercussions.

Chart showing new daily cases and seven-day moving average

Menzies said the current test protocols aren't designed for COVID.

"The rate of testing based on respiratory illnesses is based on people with symptoms presenting to testing centres. That works for influenza. For COVID-19, a fairly substantial proportion of people who get the infection and are contagious are asymptomatic or minimally symptomatic to the point that they don't go for testing," he said.

Children, in particular, tend to have milder COVID-19 infections and some never show symptoms, which means the number of cases in children and their spread is likely underestimated, he said.

Current modelling studies estimate asymptomatic cases account for more than 50 per cent of community transmission. In Manitoba, individuals are considered infectious two days prior to the onset of symptoms.

The resumption of in-class teaching this month provides an opportunity for the province to identify and contain infections, Menzies said.

"Schools, especially, are relatively easy because they have large gymnasiums and spaces that could be temporarily converted. Teachers and students are used to being regimented and can march to a room on schedule," he said.

With approximately 224,000 students and staff, a surveillance sample would see more than 22,000 people tested at an estimated cost of $3.4 million. Menzies estimated it could be completed over 14 days.

Systematic testing, including implementing mobile teams for at-risk populations, requires a massive upgrade in lab testing capacity and, until saliva sampling is more widely accepted, swabbing staff and resources.

Manitoba's current testing capacity is about 2,500 samples a day, health officials say. At that rate, a surveillance sample of the school population would require roughly nine days of exclusive use of lab resources.

"You need to think differently to control COVID-19," Menzies said. "You... shut everything down, which is effective because there's no contact between people and the infections die down (but) the consequences of shutdown are too enormous to contemplate doing that again."

 

michael.pereira@freepress.mb.ca