When will Canada's Omicron wave peak? What we know so far

The Omicron variant's spread may be slowing slightly, at least in some provinces where a government website monitoring virus projection estimates shows peak infections could be reached within a week.

In Manitoba, where the test positivity rate is now 48 per cent, this province is outpacing the rest of Canada in active COVID-19 cases. But infections could peak soon.

According to a government website that estimates trends in COVID-19 prevalence based on existing epidemiological information, Winnipeg is expected to start seeing cases decline in the next seven to 10 days.

The tool is designed for the Canadian Armed Forces to understand their risk level in different areas of Canada and internationally, and isn’t used to advise other aspects of government.

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"The tool was made available globally to provide easy access to CAF medical advisors irrespective of their location and as part of the Government of Canada open data initiative," a spokesperson told CTV News in an email.

"It is important to note that the numbers found in this model are not case numbers, but rather estimates based on existing epidemiological information.

Projections on the website are similar for Toronto, Montreal and Halifax, where cases are also expected to drop in the coming weeks. B.C.'s top doctor says the COVID-19 peak there is a few weeks away.

"We may be entering soon into the place where we will see a decline," Dr. Bonnie Henry said in an update Tuesday.

PEAK INDICATORS

University of Toronto epidemiologist Colin Furness told CTVNews.ca it is difficult to know when a peak is happening until it has actually passed.

"You can only find the peak in the rear-view mirror. We can make some guesses based on modelling about when we expect peaks to happen. But really, you don't know until you're past it," Furness said in a telephone interview Wednesday.

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Furness said there are some signals, known as leading indicators, which can show when a peak is nearing. He says these factors include adequate testing, positivity rates, and wastewater analysis.

However, with recent changes to COVID-19 testing criteria across the country, Furness says this indicator, as well as the positivity indicator, are skewed.

"If you say that only symptomatic people can get tested, your positive is going to go up. So you have to look very carefully if you want to interpret positivity as what changes if anything happens to the testing strategy, so that's dicey," he said.

While wastewater sampling can be a good leading indicator, Furness says the technique is still new and caution has to be taken on how the data is interpreted.

"When people are very sick, are they excreting a large amount of virus so it can look like there's more or could we confuse two really sick people with 10 only very slightly sick people? There's a lot we don't really know about wastewater testing," he said.

Furness noted that modelling data in December showed that the peak of this wave was expected to hit mid-January.

With this in mind, Furness said Canada is likely close to reaching the peak of the Omicron wave. However, he said it is important to remember that models are just estimates.

"[Models] can only reflect the limited understanding you have in the first place to sort of protect what might be the case," he said.

"I'm guessing that we're probably just about to peak in most places in Canada in the next week, two weeks, maybe a little bit longer than that."

To know when Canada is on the other side of the peak, Furness said there will be a "sharp, rapid decline" similar to that of the incline into the peak as waves in communicable diseases mostly tend to be symmetrical.

"Once it infects everyone who [can] be infected… all of a sudden it runs out of oxygen and it falls off quite rapidly," Furness said. "So we would expect to see not only a drop in the wastewater or positivity, it should be a rapid drop in new cases."

AFTER THE PEAK

Peak Omicron may be close, according to estimates, but predicting what happens next is more difficult.

The decline could be quick, as seen in other countries like South Africa, or it may be slower. And hospitalizations, which lag behind case counts, will continue to rise.

Experts say that in the end, Omicron will have infected millions, but it’s unknown what impact this could have on immunity for the future.

"When you think about getting infected with Omicron, the thing we certainly can’t assume is that infection from Omicron is going to give us long term immunity against other variants that might emerge," Jason Kindrachuk, an assistant professor at the University of Manitoba and Canada Research Chair in the molecular pathogenesis of emerging viruses, told CTV News. "That is something we do not know."

Shaneen Robinson-Desjarlais knows firsthand that past infection doesn’t guarantee immunity; she has had COVID-19 twice in the past nine months.

"Having almost died from COVID, saying my prayers, and getting ready to say goodbye to my family -- I was that sick," she said.

She had just delivered her baby boy when she was hospitalized with the Beta variant. Struggling to breathe on her own, it took months for Robinson-Desjarlais to recover.

Last week, a rapid test showed a positive result, and body aches and exhaustion followed.

"I believe that because I was vaccinated, this variant took it easy on my body, which I was thankful for," she said.

The severity of Omicron is also being debated. While believed to be more transmissible and able to evade some vaccine protection compared to the previous Delta variant, evidence has emerged that it may result in less severe illness and reduce the chance of being hospitalized.

Chief Public Health Officer Dr. Theresa Tam said last week that severe illnesses due to the Omicron variant are not rising at the same "explosive rate" as case numbers. However, she noted that hospitalization rates are rising because of the "sudden acceleration of Omicron and enormous volume of cases."

While the surge in cases has testing capacity stretched, resulting in underestimated case numbers, Tam said public health agencies are using other indicators like laboratory test-positivity rates to monitor the overall disease activity across the country.

"We can all help by reducing our contacts to get us through this difficult time that much faster," Tam said. "This might feel like a double marathon that we didn't sign up for, but despite feeling tired, we should have a sense of achievement for the ground we've covered so far."

With files from CTVNews.ca's Alexandra Mae Jones and Rachel Aiello