British Columbia·Analysis

B.C.'s rolling average of new cases has gone down. Here's why it doesn't matter

While we’ll still report on daily case counts when warranted, hospitalizations, people in critical care, and the positivity rate of official tests are metrics that provide a better indicator of where we are in the pandemic — and where things are headed.

Testing limits and differences with Omicron mean daily case counts are a less reliable proxy than before

People are pictured waiting in line for a COVID-19 test in Vancouver on Jan. 4. For the longest time, daily case counts were a reliable proxy for understanding the pandemic — but that's no longer the case, say experts. (Ben Nelms/CBC)

When it comes to understanding the pandemic, what numbers matter?

That's at the heart of discussions taking place in British Columbia and jurisdictions across the world as the number of Omicron cases explodes.

"We are in a different storm now," said B.C. Provincial Health Officer Dr. Bonnie Henry this week, one of several times she has alluded to the new realities of this wave of COVID-19.

And that extends to the number we've used most often to gain an understanding of our pandemic fight: case counts.

For the longest time, they were a reliable proxy for understanding the pandemic. But that's no longer the case, say people who have analyzed pandemic statistics since the beginning.

"The short answer is not with anything like the certainty we had even a month ago," said Daniel Coombs, head of University of British Columbia's mathematics department and member of the independent B.C. COVID-19 modelling group.

It's why even though the rolling average of new cases in the province went down yesterday for the first time since the Omicron wave began, nobody is taking it as a sign that the corner has been turned. 

Testing issues, virus changing

Coombs says there are two reasons for the change. 

The first is the well-documented testing capacity issues in B.C. over the past couple of weeks, and the decision to give rapid tests to many people who show up to testing sites — which are not included in the official numbers. 

At the moment, these capacity issues can be seen most clearly in Vancouver Coastal Health, where the official number of daily cases has stayed static for two weeks, despite cases continuing to rise virtually everywhere in Canada. 

The second is the decreased virulence of Omicron for many who contract the virus. It means more people who get COVID-19 in this wave will display minor symptoms, and a smaller percentage of people will end up being hospitalized. 

Case counts have always been a snapshot, and have never measured every infected person in the province.

However, Coombs said these changes mean cases are much less helpful for modelling if transmission will go up or down, or for predicting hospitalizations. 

"We're forced to extrapolate from data from other countries [further along the Omicron wave], in particular the United Kingdom," said Coombs. 

"But different countries report hospitalizations in slightly different ways. So even making an apples-to-apples comparison is tricky."

Other metrics more consistent

What does this mean in the short term? 

From a news perspective, CBC News has begun de-emphasizing daily case counts in our coverage. 

While we'll still report on them when warranted, hospitalizations, people in critical care, and the positivity rate of official tests are all consistent metrics that provide a better indicator of where we are in the pandemic, and where things are headed. 

From a health care perspective, it's expected that despite the lower virulence, the sheer number of new cases means hospitalizations will quickly rise in the next two weeks. That will create major strain on hospitals, forcing further triage in the system. 

"We're trying to basically make sure that critical elements of care are delivered, but those surgeries that can be postponed at all are," said Dr. Richard Stanwick, chief medical health officer for Island Health. 

Exactly what that will mean for critical cases, and at what point B.C. can expect a reduction in transmission, are questions much harder to get a grip on now than in the past. 

"'In the dark' is maybe just slightly too strong," said Coombs. 

"But I will say that it is difficult right now to make projections confidently, because we don't have that reliable case count information."

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