- Alberta Health was not able to provide full data updates on April 15 & 16 due to an electrical fire that affected its data centre. That has affected the daily numbers in some of the charts below.
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.
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 hospitalizations.
Patients in hospital and intensive care
While much of the reporting to date has focused on the number of confirmed cases of COVID-19, there are some issues with this data and some limitations with how it is gathered. (More on that below.)
Some experts have suggested tracking the number of hospitalizations, as well, especially as we move into the later stages of this pandemic.
This 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.
As of April 20, the data in this chart comes via Alberta Health’s COVID-19 data website.
Prior to April 20, the data was compiled from daily press briefings by Dr. Deena Hinshaw, Alberta’s chief medical officer of health, and supplemented with information from news releases or numbers requested directly from Alberta Health.
On April 20, Alberta Health told CBC News the hospital data it had been providing in these daily reports since mid-March were sometimes incomplete due to late reporting from some facilities.
The numbers in the chart are sometimes retroactively updated to reflect the latest totals, as new hospital data comes in.
Total confirmed cases
These are the numbers you’re probably most familiar with, as they’ve been front-and-centre throughout the pandemic.
But 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 go undetected because people don’t have symptoms or don’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 the past weeks, leading to changes in which cases of COVID-19 are being caught and included in the provincial data — and those which go uncounted.
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 is limited, 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 who lives 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 who have symptoms.
On April 17, Alberta Health said it would further expand testing to include asymptomatic residents and staff in continuing care facilities that are 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 who wants a test can seek one, even if they have no symptoms of COVID-19.
“Now is an opportune time to expand testing to get a full understanding of the presence of COVID-19 in our population,” Hinshaw said while announcing that expansion.
The changes in testing criteria over time will affect the case data, which is important to bear in mind when looking at these numbers.
The data in the chart above come from the daily press briefings and news releases the Government of Alberta has been putting out each afternoon for the past several weeks.
New cases by health zone
Another important measure is the number of new cases reported each day.
You can see that, to a certain extent, in the “steepness” of the curve in the total case count above.
But to make it more visible, we’ve broken it down into a day-by-day column chart below.
We’ve further broken down each column to show the number of new cases by health zone, as well.
The chart below shows cases as of when they were reported to Alberta Health, meaning data for the most recent day is not complete because it doesn’t include a full 24-hour period. (Using this method was necessary because of the data-system outage, which resulted in data not being available for April 15 and 16 as part of the province’s usual daily releases of information.)
Tap or run your mouse over a column — or a zone label — to see more detail.
It’s important to note that these numbers, too, reflect the total number of known cases.
The same issues previously discussed surrounding changes in testing criteria also apply to this chart.
Roughly six per cent of Albertans have now been tested for COVID-19 and Alberta has maintained the highest per-capita rate of testing among all provinces, although Nova Scotia has recently closed the gap and has tested nearly the same number of people, relative to its population.
The Alberta government also revealed in early April that hundreds of what it has described as “confirmed cases” were not actually confirmed by lab testing.
On April 4, Alberta Health started differentiating between “lab confirmed” and “probable” cases (defined as “symptomatic close contacts of lab-confirmed cases”). On April 5, it said 919 of the 1,250 cases to date were lab confirmed, while 331 were probable.
In this next table, you’ll find both cumulative testing volumes and daily numbers from the past few days.
Another way to look at the relationship between testing and cases is to plot them both on a single chart.
This next chart does that, with total cases on the vertical axis and the total number of people tested on the horizontal axis.
The slope of the red line shows us the number of new cases being confirmed relative to the number of people being tested. The two dotted lines offer some perspective. They show the hypothetical slopes if there were one case per 100 people tested or five cases per 100 people tested.
The background shading on chart indicates major changes in testing regimes.
(TIP: Turn your mobile device sideways to make the text on this chart appear larger on your screen.)
The testing data in both the table and the chart comes from the COVID-19 updates the province provides each afternoon.
Population data in the table comes from Statistics Canada’s population estimate for Alberta in the first quarter of 2020.
Total cases by status, including recoveries
Another statistic you’ve likely heard is the number of “recovered” cases.
At first, Alberta (and other jurisdictions) were using lab testing to determine when a person no longer had COVID-19. More recently, the province has switched to a system that relies less on testing and primarily on time elapsing (although some recoveries are still determined by doing multiple tests on the same person.)
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.
Another term you often hear is the number of “active” cases.
This includes people who are currently hospitalized and people who are not in hospital but not yet recovered.
This next chart shows the number of active cases, by health zone.
The chart begins in mid-April, as regular data on recovery dates by zone wasn’t consistently available before then.
This data comes from the province’s daily COVID-19 updates and its interactive data website.
Age of hospitalized 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.
And your perception of how vulnerable you or loved ones are to the disease may vary depending on what you consider to be “young” or “old,” so this next chart may surprise some people.
It shows the ages of people who have been hospitalized with COVID-19.
This is a cumulative total that includes patients who are still in hospital, those who have been discharged and those who have died.
This information comes via the provincial government’s COVID-19 data site.
Advanced stats and logarithmic scales
This next section may get a bit too complex for some readers, but for those who want to delve a bit deeper and make comparisons with other provinces, we thought we’d include it.
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”) — an exponential rate of growth appears as a straight line.
You can see that in the dotted line below. It represents a hypothetical rate of growth, where cases double every five days. 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.
For weeks, Ontario had a backlog of thousands of tests that had been administered but not completed.
Like Alberta, multiple provinces have also adjusted testing protocols over time due to shortages in testing materials.
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.
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