'Unusual' flu season sees jump in cases in May from lifting of COVID-19 measures

New Brunswick is dealing with an unusually late flu season, due in part to the lifting of COVID-19 protective measures in March, such as masking, says the province's acting deputy chief medical officer of health.

Normally, the flu season really starts to "take off" in January and "peters out" once the warmer weather begins, said Dr. Yves Léger.

But nearly a quarter of this season's cases have occurred this month, new statistics released by Public Health show.

There were nine cases of influenza reported during Week 18, which was May 1 to 7, the most recent statistics available. Two cases required hospitalization.

A total of 40 cases have been documented so far this season, which began Aug. 29, 2021 and continues until Aug. 27.

"So to have it start now is a bit, you know, unusual, from the trend that we've seen before, but would be explained by the lifting of the measures," said Léger.

"Since most provinces have lifted their [COVID-19] measures in the spring, we have started to see a resurgence of influenza across the country, and we're starting to see that in some of our surveillance here."

During the 2020-21 season, only one flu case was reported across New Brunswick.

By comparison, in 2019-20, at the beginning of the pandemic, there were 2,351 cases provincewide. In 2018-19, 3,008. And in 2017-18, 2,721.

The numbers are all likely underreported, noted Léger. Although influenza is a reportable disease in New Brunswick, not everyone who gets sick would necessarily go to the doctor and get tested, he said.

"But it still gives us an idea of how the infection is spreading in our communities and how that's trending."

There was once speculation that COVID-19 and flu could create what some dubbed a "twindemic," with both types of infections hitting countries at once, but those fears haven't materialized. 

Instead, some medical experts say there could be some level of "viral interference," in which a virus such as SARS-CoV-2 pushes out other pathogens at a population level for a period of time. 

Drop in immunity?

Last week, Premier Blaine Higgs remarked to reporters that "kids seem to be more vulnerable to the normal viruses and flus and bugs than they were pre-COVID.

"So, you know, I've asked the question — is there a connection here to what we would have done over the last two years with so many masking policies and the protection of everyone due to COVID? And has there been a drop in natural immunity because of that?"

The province "didn't have a choice" about the COVID measures it put in place, Higgs said. "I mean, we were dealing with a higher level threat. So we had to react accordingly.

"But I have asked the question — is there a connection here?"

'Unchartered times'

Léger contends it's too soon to know.

"I think we're sort of in unprecedented and unchartered times, really, where, you know, we've never had these sorts of measures being implemented for this long," he said.

Some experts have questioned whether there will be a resurgence of the flu and other common viruses that circulated regularly before the pandemic.

Léger said he's aware of the concerns and thinks "there is some validity to that."

Time will tell, he said.

"If we're back into a place where we don't have measures and we're seeing, you know, increasing levels of influenza, for example, next year, then that might be telling in terms of the population level immunity and what role that might have played."

No significant change in proportion of youth

Youth aged 19 and under account for 43 per cent of this season's cases, at 17 of 40.

But the proportion of cases in youth so far this season "does not differ very much" from previous seasons, said Department of Health spokesperson Michelle Guenard.

In the 2020-21 season, the province's one flu case was in a youth aged five to 19, statistics show.

In the 2019-2020 season, youth accounted for 47 per cent of the total number of positive cases.

In the 2018-2019 season, they represented 39 per cent of the total.

Increase expected to continue

Léger anticipates influenza activity among all age cohorts will continue to increase in the coming weeks.

"Things always seem to start in the West and central Canada before it sort of happens here. And this is what we're already seeing this year. So I anticipate that we'll continue to see an increase in cases before it eventually peters out," he said.

Whether the number of cases will surpass pre-COVID totals would be "purely speculation" at this point, said Léger.

He noted respiratory viruses typically have a seasonal pattern — they tend to rise in the late fall and winter and then drop down again in the spring when the weather improves and people are outside more and distanced, giving the viruses less opportunities to spread.

"So because this increase is happening in an unusual time, it's hard to know exactly how it's going to behave."

Still, Léger said he doubts New Brunswick will see a bigger influenza season than before.

Other types of infections, such as the common cold, are more difficult to predict, he said, since they are not reportable diseases, so there's no way to know exactly how they're trending.

Unlike the flu, there are no vaccines to protect against these other illnesses, but people can still take measures to protect themselves and others, he said.

These include wearing a mask indoors in crowded places, physical distancing and staying home when sick.