Here are the latest COVID-19 statistics for Alberta — and what they mean
CBC will update these charts regularly as new information becomes available
As the COVID-19 pandemic continues, there are so many numbers flying around, it's hard to keep track.
Here, we'll do our best to keep track for you.
- NEW as of Aug. 5: Scroll down for an interactive map of active cases
Below you'll find a series of curated charts, which will be updated as new information becomes available.
You'll also find brief descriptions of how the data is measured, what it shows — and what it doesn't show. This context is important to make sense of the numbers.
We'll start with new cases.
These are the figures that tend to be front and centre in the daily updates about COVID-19.
There are some issues with relying on new-case data, alone, as the number of cases you detect is related to the amount testing you do and who you're testing (more on that in a moment).
But the advantage of looking at new cases is that they tend to be a leading indicator of how the virus is spreading, where it's spreading, and whether the spread is speeding up or slowing down. And, at this point in the pandemic, Alberta is offering COVID-19 tests to anyone who wants one, so there are fewer concerns about the data being affected by limited testing availability.
This first chart shows us the number of new cases identified each day since mid-March, and a seven-day average of daily new cases.
Of course, Alberta is a big province, and outbreaks of the novel coronavirus often happen in localized areas.
At various times throughout the pandemic, different parts of the province have seen different degrees of spread.
So it's also useful to look at the where the new cases are happening, too.
Alberta Health breaks the province down into five broad health zones: South, Calgary, Central, Edmonton and North. (The names are pretty self-explanatory but if you want to see the precise boundaries of each zones, here's a link to a PDF map.)
This next chart shows new cases, by day, broken down by health zone.
Each column in this chart is a "stack" of cases, colour-coded by zone. Each "stack" adds up to the total number of new cases identified that day.
You can see how cases really started ramping up in mid-April in the Calgary Zone, in particular. This was largely related to the major outbreak at the Cargill slaughterhouse in High River, which is part of the Calgary Zone.
Later in April, you can see a large number of new cases in the South Zone. This was related to the outbreak at the JBS slaughterhouse and the wider outbreak in Brooks at that time.
And, in early June, you can see how new cases started growing in the Edmonton Zone again, after very few cases in and around the city for many weeks. The beginning of this trend was initially linked to several family gatherings in the city.
So that's the big picture, but the chart above can be a little hard to read if you're mainly interested in recent cases.
This next chart shows the same information, but is limited to just the past three weeks, making it easier to see where new cases have been popping up.
Some of these new cases will require hospitalization, which leads us to the next metric.
While much of the reporting to date has focused on the number of cases, experts have suggested tracking the number of hospitalizations, as well.
Hospitalization data is more of a lagging indicator, as it typically takes longer for someone who gets sick with COVID-19 to end up in hospital than it does for them to test positive for the virus. There can also be delays in reporting from the hospitals, themselves, further adding to the lag in the aggregated data.
Still, tracking hospitalizations is useful because it not only helps gauge how much the disease has spread but also helps keep track of how much strain is being put on the health-care system. Hospital resources, of course, are finite and, in other parts of the world, COVID-19 cases have pushed those resources to — or beyond — their capacity.
Alberta hospitals had an existing capacity of 295 intensive-care-unit (ICU) beds, in total, prior to upgrades and expansions undertaken in response to the pandemic, according to COVID-19 modelling released by the province.
As of early April, there were 158 ICU beds available for COVID-19 patients. Plans were enacted to expand that availability to as many as 1,081 by late April, if necessary, by adding more beds to existing ICU rooms and converting other hospital space into new ICU capacity.
This next chart shows the number of patients in hospital — both those in intensive care and those outside of an ICU — each day since mid-March.
Note: There is currently a glitch in the data system that Alberta Health has identified and is working to resolve. It has to do with recent outbreaks within hospitals, where patients have caught COVID-19 after being admitted for other ailments.
- Misericordia hospital's outbreak linked to dozens of COVID-19 cases
- Red Deer hospital restricts visitors after COVID-19 outbreak
- COVID-19 outbreak confirmed at Peter Lougheed hospital in Calgary
The province's data system codes the date of a COVID "patient" by their date of admission to hospital, so these patients, many of whom had been in hospital for days or weeks but only caught COVID-19 more recently, are being counted as COVID patients based on their date of admission.
This has resulted in cases for previous weeks and months appearing retroactively elevated.
(You can read more about the details here.)
The glitch means the data should be interpreted with caution. But prior to the glitch, it was evident that hospitalizations had peaked in late April and then, after declining in May and June, started rising again in July.
To date, hospitalizations have not reached a level anywhere near the capacity of Alberta's health-care system.
Still, it remains an important measure that public-health officials monitor closely.
To provide some further context, this next chart shows the hospitalization rate in the four largest provinces.
This is a population-adjusted measure, calculated as the number of patients in hospital per million residents.
Note the numbers in the above charts are sometimes retroactively updated to reflect the latest totals, as new hospital data comes in.
Active and recovered cases
Another term you often hear in discussion of COVID-19 is the number of "active" and "recovered" cases.
In general, Alberta Health says a recovered case is defined as:
- Anyone who is healthy after 14 days have passed, if they did not experience severe symptoms requiring hospitalization.
- Anyone who has gone 10 days from their date of discharge from hospital, if they did require hospitalization.
- Anyone who has received two negative tests, at least 24 hours apart.
This next chart depicts the total number of cases, broken down by the status of the patients: recovered, not-yet-recovered (but not in hospital), hospitalized or deceased.
Again, this chart is a "big picture" look at the impact of the disease, provincewide.
But the number of active cases can vary quite a bit from place to place and from time to time.
So this next chart focuses on just the past three weeks, and breaks down the active caseload by health zone.
Beyond these five broad zones, Alberta Health breaks down the geography of the province even further.
It also subdivides those zones in 132 "local geographic areas" or LGAs. (You can find more information about these areas here.)
The right-hand column in the table below shows the latest active caseload for each of those local areas. The mini line charts in the adjacent column show the caseload history for each area. (Note the scale of vertical axis is not the same for each line chart; it's specific to each local area's case history.)
The table is sorted from highest to lowest, by default, but you can change the sorting by clicking on the column header of area names so they are sorted alphabetically, instead.
The table may not display fully on mobile devices or small screens. In that case, you can also click here to open a standalone version in a new browser tab.
You can also see active cases by local health area on the following interactive map. Scroll, zoom and click on the map for more information.
The map shows both the active case numbers (the purple dots) and the active-case rates per population (the background shading.)
If the map isn't displaying well on your mobile device, click here for a standalone version.
Total confirmed cases
The term "flatten the curve" has become a common phrase used by people when referring to stopping the spread of the COVID-19.
One "curve" in particular that people have been paying attention to is the total number of cases.
Early in the outbreak, the number of cases was growing rapidly, with the total doubling every three days.
Later on, that rate of growth started to slow, and the curve "flattened" — to a degree. The outbreaks at the slaughterhouses in High River and Brooks, in particular, shot it back up again, as have smaller, localized outbreaks in other areas.
The red line in this next chart shows the cumulative total of COVID-19 cases in Alberta, starting from the first day that 50 total cases were recorded.
The background shading shows various stages of the province's public-health measures, from the initial pandemic response (colloquially referred to as the "lockdown") to Stage 1 and Stage 2 of the "re-launch" strategy.
When looking at total cases, it's important to bear in mind that the number of confirmed cases doesn't represent the number of actual cases — a figure we simply don't know.
Many cases may have gone undetected because people didn't have symptoms or didn't seek testing for other reasons. People who have wanted a test haven't always been able to get them, especially early in the outbreak.
Alberta's testing protocols have changed significantly over time, leading to changes in which cases of COVID-19 are being caught and included in the provincial data — and those which go uncounted.
Alberta has also had one of the highest rates of testing in Canada, as illustrated in this next chart.
You can click or tap on the above chart to switch between per-capita testing rates and absolute testing volumes.
How testing has changed over time
It the earliest stages of the outbreak, testing focused on international travellers returning to Alberta and their close contacts.
On March 23, the province imposed stricter limits on who could get tested, giving a higher priority to those most at risk from COVID-19 and to health-care workers. Given that testing capacity was limited at that time, there were some important reasons for doing this, in order to get the maximum benefit out of the tests that were available. As testing capacity increased again, however, the criteria began to expand.
On April 7, the province started opening up tests to more symptomatic people, including a wider range of front-line workers such as firefighters, police and public-health inspectors, as well as anyone over the age of 65.
On April 8, the criteria were further expanded to include anyone with symptoms living in the Calgary health zone, which has seen the majority of cases so far in the province.
On April 14, the criteria were expanded again to include all Albertans showing symptoms.
On April 17, Alberta Health said it would further expand testing to include asymptomatic residents and staff in continuing care facilities experiencing outbreaks.
On May 11, asymptomatic testing was extended to people in the Calgary health zone, due to the high number of cases in the area. Similar asymptomatic testing was later offered in Brooks, as well, after the major outbreak in that city.
On May 29, asymptomatic testing was expanded to the entire province, meaning any Albertan wanting a test could seek one, even without symptoms of COVID-19.
All this has led to major fluctuations in the number of tests being performed and who was being tested.
It's important to bear these changes in mind when considering another measure health officials track: the positivity rate. This is simply the percentage of tests that come back positive.
This next chart depicts the positivity rate in Alberta over time.
Each dot depicts the percentage of positive tests on a given day. The line shows the average positivity rate over the previous seven days.
The background shading and annotations show major changes in the testing protocol over time.
Age of patients
We've heard that COVID-19 tends to hit older people harder than younger people, and this is true to a large extent but it doesn't mean young people are immune.
This next chart shows the age ranges of patients who have been hospitalized in Alberta with the disease.
The numbers in this chart are cumulative totals that include patients who are still in hospital, those who have been discharged and those who have died.
The number of people to have died from the disease is much more heavily weighted toward older adults, with most of the deaths among people aged 80 or over. Many of these people have died in long-term care homes.
This next chart shows the total cases in Alberta, broken down by both the age and status of the patients.
The final section is next. It gets a bit more complex but, for those who want to delve a bit deeper and make comparisons with other provinces, we thought we'd include it.
Advanced stats and logarithmic scales
If you've been following the COVID-19 case data closely — in Canada and around the world — you'll likely have seen some charts presented on a logarithmic scale. (Specifically, a logarithmic vertical axis.)
These types of charts are useful to visualize rates of growth when things grow exponentially, like COVID-19, where each day's growth is a percentage of the previous day's total cases.
That type of growth leads to curves that start out fairly flat and then shoot up rapidly, making visual comparisons difficult, especially between jurisdictions that are farther along in their local epidemics.
But by using a logarithmic scale — where each step on the vertical axis is 10 times larger than the previous step (think "10, 100, 1,000" instead of "10, 20, 30") — exponential rates of growth are easier to visualize.
In this final chart, the coloured lines represent COVID-19 cases in different provinces, starting from the day each province first recorded at least 50 cases.
It's important to note that testing protocols vary from province to province, which will affect their case numbers.
Note in particular that Quebec changed its reporting method around Day 6 in this chart, when it no longer waited for secondary lab confirmation to count a case as confirmed. This cleared a backlog, and led to the sharp and sudden rise in cases that day.
Like Alberta, multiple provinces have also adjusted testing protocols over time.
All told, that means the above chart is not exactly an apples-to-apples comparison but — with all these caveats in mind — it still offers some sense of where we're at in our COVID-19 spread, relative to other parts of the country.
The COVID-19 situation continues to evolve rapidly. If you have an idea on how to improve the presentation of these data, or data that you would like to see that's not here, please email firstname.lastname@example.org. You can also contact Robson on Twitter @CBCFletch and join the discussion there.