The more contagious Delta variant of concern is behind a growing number of COVID-19 infections in Manitoba, as the strain outpaces other mutations ahead of an anticipated fall wave.
While the Delta variant is not yet dominant in the province, the proportion of cases detected in Manitoba increased by 10.9 percentage points from July 11 to Aug. 1, provincial officials reported.
During the final week of July — the most recent data available — Delta (B.1617.2) made up 33.7 per cent of all COVID-19 cases reported in Manitoba, causing more infections than the Alpha variant (B.1.1.7), which fuelled the devastating third wave.
About 32.7 per cent of cases in the same period were caused by a virus strain that was not a variant of concern, the province said.
However, out of the seven variants found in the province, Delta is at the front of the pack.
And with Delta on the rise, deputy chief provincial public health officer Dr. Jazz Atwal said pandemic models forecasting how it may affect the community are still being calibrated and reviewed.
"We’re just trying to understand the risk related to the model, and look at all those other things that are occurring as well — with vaccine uptake, with acute-care capacity, with the other impacts that measures have on people’s health as well," Atwal told reporters during a briefing on Monday.
He said the provincial model has 290 parameters built into it, including Delta and COVID-19 immunization.
"As soon as public health has reviewed it and has come to some conclusions related to it as well, we will be providing that to the public," Atwal said.
"Modelling is only one aspect of our risk assessment in relation to COVID-19 and the measures that public health would be recommending," he emphasized.
Public health has been criticized for withholding its latest model as it removed protective measures, such as the indoor mask mandate on Aug. 7.
The model illustrates a range of transmission and hospitalization scenarios based on public health measures, the behaviour of Manitobans, increased transmissibility of Delta, and the protection offered by vaccines.
A provincial spokesperson previously told the Free Press a version of the model was completed in late July.
Officials have said they need more time to verify the model and its results, noting small errors could have a "tremendous" effect. Staff departures have contributed to the delay.
Nazeem Muhajarine, a University of Saskatchewan professor of community health and epidemiology, said the Delta variant and mixed levels of vaccine coverage have made the pandemic landscape "immensely complicated."
"Manitoba public health is not alone in that predicament — the lack of confidence — because of the many different variables under consideration, and the assumptions that go into these models are all over the map," Muhajarine said, adding Saskatchewan officials have yet to release their models.
"The models are as good as the data that goes into it, so if the data is incomplete or suspect, then what comes out of the model is not great."
Throughout the second and third waves of the pandemic, Muhajarine said public health response across the provinces seemed to align with the monitoring of cases and hospitalization relative to capacity, rather than modelling data available at the time.
"I don’t think the modelling has really been what is driving, and drove in the past, public health measures," Muhajarine said.
Rather, pandemic models have been used to help people understand the threat of COVID-19, and presenting updated forecasts and a "worst-case scenario" for Delta may influence the public to stick to public health measures, Muhajarine said.
However, even without a model, the province has the knowledge and experience to lessen the impact of a fourth wave, and most importantly improve vaccine uptake, Muhajarine said.
"In Manitoba, Winnipeg, Brandon and so on, there will be pockets of populations that have very low rates of vaccine uptake, and you don’t need a model to forecast that," he said.
"There’s still a lot of information available to us that we can act on — that we need to act on — on an ongoing basis."
Danielle Da Silva
Danielle Da Silva is a general assignment reporter.