When will we know if we are 'flattening' the COVID-19 curve in Alberta? Not for a while still

How many more COVID-19 cases today? How does that compare to yesterday? Are we "flattening the curve" yet? The answer, according to experts, is: be patient.

'It won't be over the next few days,' says Dr. Deena Hinshaw. 'It will be over the next few weeks.'

Alberta chief medical officer of health Dr. Deena Hinshaw updates media on the COVID-19 situation in this file photo. (Jason Franson/Canadian Press)

We've been cancelling our plans, minimizing our trips to the grocery store and having drinks with friends over Skype instead of a bar table. Many of us are working from home, working less or have lost our jobs altogether. We're struggling to find child care and can't take our increasingly antsy kids to the zoo, or even the playground down the street.

All this in the name of "flattening the curve." But is it making a difference?

That question is on a lot of minds as Albertans continue to hunker down in their homes, wash their hands obsessively and tune in daily to hear the latest case numbers from Dr. Deena Hinshaw.

How many more COVID-19 cases today? How does that compare to yesterday? Is that damn curve getting any flatter?

The answer, according to experts, is: be patient.

This virus takes a long time to incubate, they note. And although Alberta has managed to complete more tests, more quickly, than any other province, it can still take days between getting a swab up your nose and getting your results. All this adds up to a pretty significant lag time between the social-distancing measures we take and the effects of those measures showing up in the daily case counts.

It's too soon to say if we're out of the woods.

But there is some good news, at least compared to how things are going elsewhere. 

'At least we've blunted the curve'

At this point, the primary goal is to avoid overwhelming our health-care system with a sudden surge of cases it can't handle.

We've seen the horrific consequences of that in Italy and Spain, where hospitals are overwhelmed and mortuaries are, too. People living in New York are being told to brace for a looming surge, as well, as cases and deaths in the state continue to rise rapidly.

Compared to places like these, Dr. Craig Jenne says Alberta seems, so far, to be on a better path.

"Definitely compared to Europe, compared to the United States, we have seen much less community-level sharing of this virus," said Jenne, a professor of microbiology, immunology and infectious diseases at the University of Calgary.

Craig Jenne teaches microbiology and infectious diseases at the University of Calgary. (Jennifer Lee/CBC)

While it's too soon to know if we're flattening the curve, Jenne said Alberta seems to have gotten off to a better and faster start in its response to the COVID-19 outbreak.

"At least we've blunted the curve," he said.

That may be hard to see, looking at the latest numbers. Tuesday saw 57 new cases of COVID-19 confirmed in the province, marking the largest single-day increase to date, and bringing the total number of known cases to 358.

But consider it this way.

China, at the most rapid stage of its outbreak, saw the number of COVID-19 cases doubling every two days. So too, did Italy and Iran.

Alberta's cases, by contrast, have been doubling roughly every three days.

That may not sound like a big difference. But look at the chart below to see how quickly it adds up.

If anything, the rate of growth appears to be slowing, ever so slightly — in the chart, at least. (Whether that reflects an actual change in the rate of spread, in reality, is another question, one that requires more evidence to determine with confidence.)

But for the sake of reading the chart: See the lower dotted line? That indicates a doubling-every-three-days pace. The red line, which indicates confirmed cases, was above that dotted line a week ago but, as of yesterday, crossed just below it, indicating the pace of the expansion has slowed.

Of course these are early figures and not yet cause for celebration. The number of cases will continue to grow, but that is expected, almost inevitable, at this point. What experts are watching for the time being, at least, is that rate of growth.

"The whole thing is about the rate of increase," said Dr. Lynora Saxinger, who studies infectious diseases at the University of Alberta.

"If each person is infecting less than one other person, it will turn around."

For now, though, that's not the case. And she expects the number of new COVID-19 infections will continue to rise for some time, even with the steps we've taken to to fight the spread of the disease.

A lot of the growth we're seeing at the moment, she says, has effectively been baked in. The infections happened before many social distancing measures were put in place.

"Everyone who's getting sick now was probably in contact with someone before the restrictions, and it takes sometimes seven to 14 days to develop symptoms that are noticeable," she said. "So what we're seeing right now still reflects what was happening before we started making the changes in our social structure."

Still seeing exposures of 'up to 2 weeks ago'

Dr. Deena Hinshaw, Alberta's chief medical officer of health (and, increasingly, a household name in this province) says it's important to bear in mind the time it takes from infection to test outcome.

"We need to remember that, because the incubation period is 14 days, it would take two weeks from whenever we implemented any new measure for us to see what effect that might take," she said.

"So I think we should expect that there will be additional new cases that we will see, because we're still seeing after-effects of exposures that happened up to two weeks ago."

'Danger' tape blocks off a playground in Calgary. As of Monday, March 23, the city has told parents not to allow their children to use the equipment, for fear it will spread the coronavirus that causes COVID-19. (Robson Fletcher/CBC)

Another thing to remember is that the social-distancing measures didn't happen all at once. New protocols have been gradually introduced, virtually day-by-day, and it takes time for people to learn them, get their minds around them and comply.

All that further adds to the lag time between social-distancing measures and, hopefully sometime down the road, reduced infection rates.

"It won't be over the next few days," Hinshaw said. "It will be over the next few weeks."

In the grand scheme of the pandemic, Jenne is cautiously optimistic about where Alberta finds itself.

"We are truly flattening the curve compared to what could be happening," he said.

"Does it have to be flattened further? Absolutely. If we don't want to overrun hospitals, we've got to slow this down even further. But if you compare this to Italy, to Spain, to the United States, we are outperforming some of our close friends. And, as a result, we've pushed this curve."


  • The two paragraphs below the second chart have been amended to make it more clear that the slight decrease in the growth rate of confirmed cases in that chart does not necessarily reflect an actual change, in reality, given the limitations of the available evidence, to date.
    Mar 25, 2020 1:03 PM MT


Robson Fletcher

Data Journalist / Senior Reporter

Robson Fletcher's work for CBC Calgary focuses on data, analysis and investigative journalism. He joined CBC in 2015 after spending the previous decade working as a reporter and editor at newspapers in Alberta, British Columbia and Manitoba.

With files from Jennifer Lee and Carolyn Dunn