As BA.4 and BA.5 take hold, experts say a summer wave of COVID-19 is underway

As summer festivals get underway across Canada, so too has another wave of COVID-19, experts warn.

"There is a potential for things to get substantially worse if we're not a little bit careful and don't take some basic steps to try to mitigate the spread of these variants," Dr. Christopher Labos, a Montreal-based epidemiologist and cardiologist, told CTV News.

The more infectious BA.4 and BA.5 Omicron subvariants are expected to make up a larger share of all COVID-19 cases in Canada.

Labos says people may be more vulnerable if more time has passed since their last vaccine dose.

He also noted Canada's provinces and territories have lifted many of their public health restrictions, including masking requirements.

"If you're going to be indoors with a bunch of other people breathing the same air, I don't know why you wouldn't want to wear a mask at this point, because it's going to prevent the spread of the virus and it's a low-cost, low-risk way to do that," Labos said.

The Ontario COVID-19 Science Advisory Table estimates that COVID-19 concentrations in wastewater are already half of where they were during the peak of the last Omicron wave in April and could reach those heights in a few weeks.

"The data that we're looking at now is obviously not the best of news in July. We're seeing significant increases in the wastewater signal," Robert Delatolla, a professor at the University of Ottawa who has done research into wastewater treatment and disease surveillance, told CTV National News.

Increases in the wastewater signal could serve as a leading indicator for what may come in terms of COVID-19 cases and hospitalizations, as is the case in Quebec.

"I think it's good in terms of communication so that the public knows, so people can make their own decisions in terms of what they're doing. Whether they want to mask again, whether they're going to go to certain events or not, and if they do those events maybe with masking or without," Delatolla said.

Meanwhile, staffing shortages in hospitals are adding another strain to the health-care system.

The matter is expected to be a topic of discussion at the next meeting of Canadian premiers in Victoria this week, with continued calls for the federal government to increase its share of health-care spending.

With files from CTV News and The Canadian Press