A tale of 2 Prairie provinces: Why the Manitoba-Saskatchewan COVID-19 divide doesn't matter
Disparate case numbers too low to be significant this early in pandemic: health expert
In many ways, Manitoba and Saskatchewan are mirror images of each other.
They both have conservative premiers. They both love curling and the Canadian Football League. They rank fifth and sixth in population among the provinces — and the other way around in terms of size.
Yet in these early days of the COVID-19 pandemic, there's a stark difference between the two neighbouring Prairie provinces.
As of Tuesday evening, Manitoba reported 21 confirmed or probable cases of the disease while Saskatchewan disclosed 72.
This means Manitoba has the lowest number of known cases of the disease among all Canadian provinces on a per-capita basis — while Saskatchewan owns an apparent infection rate that's four times higher.
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In general terms, both provinces are looking for the disease in a similar manner.
To date, Manitoba has tested 4,520 of its 1.38 million residents, which means 0.3 per cent of the population has been sampled.
Saskatchewan has just under 1.2 million people and has tested 5,757 of them, or 0.5 per cent of the populace.
Both provinces are also focusing their testing efforts on people with COVID-19 symptoms who have returned from international travel or have been exposed to known cases of the disease. Manitoba is also testing symptomatic health-care workers, people on First Nations and patients in intensive care units or personal care homes.
The question is why Saskatchewan is presenting so many more cases in comparison to its eastern neighbour.
"It's a good question but I don't have a good answer about why we are different," said Dr. Saqib Shahab, Saskatchewan's chief medical health officer.
Dr. Brent Roussin, Manitoba's chief provincial public health officer, said he does not know enough about Saskatchewan's epidemiology to offer an informed opinion.
He surmised one possible explanation: Saskatchewan's neighbour Alberta, where COVID-19 is moving from person to person within the community, rather than jumping from people who have returned from international travel.
Saskatchewan has "much more proximity to a province that has have been showing community transmission," Roussin said Tuesday, adding Saskatchewan is more likely have imported the disease from Alberta.
Community transmission appears to be the cause of at least four of Saskatchewan's 72 cases, Shahab confirmed Tuesday.
"You have to act anywhere in Saskatchewan as if there's unknown human transmission," he said.
Steven Lewis, a Saskatoon-based health policy analyst, said the confirmed presence of community transmission in Saskatchewan means it's reasonable to expect the number of cases in that province to rise more quickly in the near future than they will in Manitoba, where there is no evidence the virus is jumping from person to person just yet.
That does not, however, explain why Manitoba and Saskatchewan's numbers are so different right now, Lewis said.
In fact, the discrepancy between the two provinces is irrelevant at this stage of the pandemic, he said.
"The numbers are still small in both provinces and at the beginning of an epidemic, you will typically see pretty much random variation in pockets of outbreaks," Lewis said in a telephone interview from Melbourne, Australia.
"So it could just mean that [Saskatchewan is] a couple of days ahead of Manitoba. It may mean that for some reason the people who presented for testing in Saskatchewan were a little more symptomatic than the people in Manitoba.
"It may be just a matter of bad luck, in the sense that maybe a couple of travellers from elsewhere returned to Saskatchewan and were asymptomatic and started spreading a little bit and Manitoba hasn't experienced that yet."
Lewis said he would be inclined to discern a difference between the two provinces if Saskatchewan had 12,000 cases of COVID-19 compared to 2,000 in Manitoba.
In other words, looking at case numbers of 72 and 21 right now and deciding there's a difference between the two provinces is kind of like predicting an election result on the basis of a handful of early-reporting polls.
As well, neither Manitoba nor Saskatchewan have the capacity to conduct random COVID-19 sampling among their general population, as the World Health Organization has advised.
Manitoba in particular is struggling to process COVID-19 tests due to a shortage of reagent, the chemical compounds used in two stages of the genetic test for the coronavirus that causes the disease.
One reagent breaks apart the lipid shell of the virus, allowing access to the genetic material inside. Another reagent effectively copies the genetic material by turning RNA into DNA.
This is why Manitoba is only testing a handful of categories of suspected COVID-19 carriers. Roussin said he's confident community transmission is not happening in a significant manner in Manitoba yet because few people are turning up at emergency wards with serious COVID-19 symptoms — and no one has tested positive at a Manitoba hospital yet.
This does not, however, mean community transmission isn't happening in Manitoba. Roussin is expecting that to happen in the coming weeks.
Without random sampling, there really is no way to tell how many people are walking around with the virus in both provinces, unbeknownst to themselves.
"Some epidemiologists have speculated that there could be 10 or 100 times more cases out there that are completely asymptomatic. And since we don't yet have the capacity for mass population testing, we really don't know the prevalence rate," Lewis said.
"We know the number of tests we've done and then we know the number of positive tests, but if there are 50,000 people in Manitoba or Saskatchewan who actually are carrying the virus, we don't know that that's the case. But it's not beyond the realm of possibility."
This is why both provinces are recommending social distancing and warning people to be very careful about their hygiene.
"That's not a reason to panic," Shahab said of community transmission. "It's a reason to be very thoughtful about day-to-day activities. You're going shopping, you bring your groceries home … you wash your hands."
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