Albertans diagnosed with COVID-19 are younger and end up in hospital less often. This is likely why

If you look closely at the numbers coming out of Alberta, you'll notice something strange — especially compared to B.C. and Ontario.

Testing protocol may have been 'catching more cases that were going undetected in other provinces'

An Alberta Health Services worker speaks with a driver at a drive-thru testing facility in Calgary in this file photo from March 27. (Jeff McIntosh/The Canadian Press)

Tracking COVID-19 statistics has become somewhat of a pandemic hobby, and if you look closely at some of the numbers coming out of Alberta, you'll notice something strange.

Albertans diagnosed with the disease tend to be much younger — and end up in hospital far less often — than those in other large provinces with significant outbreaks.

This was true even prior to the major outbreaks at two meat-processing plants in Alberta, which involve many working-age people and their families, and now make up the bulk of the active cases in the province.

Before cases at Cargill and JBS Foods exploded, sending Alberta's numbers skyward just as other provinces' curves started to flatten, the apparent demographics and severity of the disease still stood in stark contrast to the data coming out Ontario and British Columbia.

Alberta, of course, has a younger population than other provinces — but not that much younger.

The differences in COVID-19 cases are greater than you would expect from the demographic differences alone.

Differences beyond demographics

Kids and teenagers make up about 25 per cent of the population in Alberta, which is high relative to other provinces, especially B.C., where it's only about 20 per cent.

So, to a degree, you might expect more kids and teens to contract COVID-19 in Alberta, just because they make up a greater share of the population. But the age distribution of the disease looks quite different from that of the general population.

Again, this was evident even a couple of weeks ago — before the worst of the meat-packing outbreaks started to show up in Alberta's data.

Back in mid-April, Alberta and B.C. had similar total caseloads, but Alberta had confirmed 191 cases of the disease among kids and teenagers, compared to just 17 in B.C.

There were similar discrepancies at the other end of the age spectrum.

People aged 80 and over made up more than 15 per cent of total cases in Ontario, while they accounted for less than six per cent of cases in Alberta, even though the proportion of cases from long-term care homes were roughly the same in both provinces at that time.

The numbers coming out of Alberta stand in such stark contrast to other parts of the country that its chief medical officer of health believes they don't reflect real differences in the behaviour of the virus, but stem primarily from differences in testing protocols.

"I don't think there's any reason to believe that we have a different kind of spread; I believe it's more about who we're testing," Dr. Deena Hinshaw said.

"My hypothesis would be that we've been able to catch more of the younger cases because we have been able to test so many more people."

In the early days of the outbreak, Alberta tested more people than any other province, even those with much larger populations such as Ontario and Quebec.

Alberta still tests the most of any province, per capita (although Nova Scotia has almost caught up). And, apart from a couple of weeks in late March and early April, the testing in Alberta has been widely available to people of all ages.

So it stands to reason that more young Albertans have been tested compared with other provinces, but we can't say precisely how many more, because most provinces don't release the same kind of data.

Dearth of data

Currently, Alberta and New Brunswick are the only provinces that publish testing data that includes the ages of all people tested — including the negative tests.

The dearth of data makes things challenging, says Simona Bignami, a professor of social statistics in the department of demography at the University of Montreal.

"In places like Alberta … where there was very wide testing, it's very hard to make comparisons with other provinces that tested to more narrow criteria," she said.

But another way to look at the data that does exist is in terms of the percentage of confirmed cases which result in hospitalizations. And again, Alberta looks quite different.

As of April 13, just six per cent people who were determined to have COVID-19 in Alberta ended up in hospital.

That compares to about 13 per cent in Ontario and 23 per cent in B.C.

Cases likely going 'undetected in other provinces'

This doesn't necessarily mean COVID-19 patients in Ontario and B.C. are more susceptible to the disease than patients in Alberta.

It could mean people with less severe cases of the disease aren't getting tested as often in those provinces as they are in Alberta.

To date, Alberta has tested roughly twice as many people, per capita, as both B.C. and Ontario.

It's hard to say for sure, without more robust data that's comparable between provinces, but Bignami also believes this is a more likely explanation for why Alberta's COVID-19 cases appear so much younger and less severe, relatively speaking.

"If I would have to make a conclusion, I would say it's almost completely the result of the testing criteria," she said.

"I think they were catching more cases that were going undetected in other provinces."


Robson Fletcher

Data Journalist

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.


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