Past the peak? Ontario flu cases fall but virus still circulating widely

Public Health Ontario’s latest findings reveal influenza rates have been decreasing throughout the province but still recommends vaccination as the best defence

Despite a dip in cases and hospital admissions at the start of the year, Ontario continues to experience a challenging flu season and experts say precautions like vaccinations are still well worthwhile for those who haven’t gotten them.

“We are starting, thankfully, to see hospitalization rates due to flu begin to decrease, which I think is good news, as we return to work and school after the holidays,” Ontario Hospital Association Vice President Melissa Prokopy told CP24.com. “The volumes are still pretty high within hospitals, but the data is suggesting that perhaps we peaked.”

New data released by the province Friday show that while influenza activity remains high, it dipped over the past few weeks, suggesting that it peaked over the holiday period.

“Influenza activity declined over the past two weeks, indicating the peak in activity occurred during the week of December 14-20,” Public Health Ontario (PHO) said on its website.

The data show a sharp rise in cases starting at the end of October, peaking at around 41.7 cases per 100,000 people on Dec. 14. That number was down to 24.8 cases per 100,000 people by Jan. 3.

“Just to put it in context though, the percent of tests coming back positive is still 25 per cent, which is quite high, which suggests that there is still a lot of virus floating around in the community right now,” said Fahad Razak, an internist at St. Michael’s Hospital and Canada Research Chair in Healthcare Data and Analytics at the University of Toronto.

H3N2 strain continues to affect young kids

There was a total of 4,066 influenza cases in Ontario from Dec. 28 to Jan. 3.

Most flu cases are still occurring in those aged 60 and up. However, H3N2, a type of Influenza A that has been dominant this flu season, continues to affect young children.

PHO said that while Influenza A percent positivity has declined in all age groups, it remains highest in children aged 5-11 at 34.3 per cent and kids aged 1-4 at 40.7 per cent.

“Historically, when H3N2 occurs, then typically we have worse flu seasons,” Razak said. “But historically, it has been flu seasons that will disproportionately affect elderly patients. This year, because of probably some additional mutations that have occurred, it has also hit children very hard.”

While many people tend to think of flu shots as being more important for elderly people, Razak said the data underscores the importance of vaccination for all eligible individuals.

“A really important part of the message is that this is a vaccine for everyone over the age of six months, everyone. It’s not just a vaccine for the elderly,” he said.

He pointed out that by some estimates, more than 90 per cent of all children who end up in hospital with critical illness from the flu are unvaccinated.

“And so the value of the vaccines for kids is incredibly high,” Razak said.

He also said that while the flu vaccine is not always a strong match for the dominant strain, it generally remains quite effective at preventing more serious illness in those who do get infected.

ICU admissions climbed, likely due to secondary risks from flu

That point was highlighted by the continuing rise in ICU numbers, despite lower hospital admissions.

Ontario hospital admissions for flu patients declined from a peak of 1,400 the week of Christmas to 1,095 the week of Dec. 28 to Jan. 3. While there are still 1,209 people in hospital with the flu, that’s down slightly by 42 people compared to the previous week.

However, ICU admission for flu patients continued to rise the week after Christmas, going from 130 to 142.

For comparison, there were just 52 people in Ontario ICUs with the flu around the same time last year.

“Often the challenge is with secondary infections, and the flu especially is a really important example of this,” Razak said.

In kids, a secondary bacterial pneumonia will often settle in a couple of days after a severe bout of the flu, Razak said.

“So flu is a virus, but it weakens and erodes and damages lung tissue, and then a really severe bacterial infection sets in, and that ends up being what results in people coming to hospital,” he said.

In adults, the risk of having a heart attack or stroke goes up by 300-500 per cent in the weeks following a flu infection, he pointed out.

“Because the flu itself is such an enormously inflammatory infection, when it happens, it then triggers these downstream effects like the heart attack or the stroke. So we see that consistently,” Razak said. “And again, it highlights the value of vaccination, because it reduces the severity of infection.”

Those who haven’t gotten a shot so far this year could still benefit from it, especially if there is a spring wave of flu infections as sometimes occurs, he added.

Hospitals strained but managing

Prokopy said that while hospitals are managing, the active flu season has exacerbated long wait times and other pressures on the system.

“As influenza activity is high in the community, it starts to increase emergency department visits and hospital admissions, and when you kind of compound that with just the general kind of pressures on the system, the kind of access and capacity issues that the system is already facing, it puts added pressure on bed capacity, on wait times, on staff,” she said.

Razak said the problem is a “Canada-wide phenomenon,” pointing out that in Alberta the organization representing emergency room physicians has asked the government to declare a state of emergency because the high influx of patients has made it difficult to run emergency rooms.

“When hospitals have overwhelming volume like we’re experiencing now, everything slows down. So it’s harder to provide care for any condition that comes into hospital,” Razak said.

Prokopy said there are simple things that members of the public can do to help mitigate the spread of infection. Those include hand washing, covering sneezes and coughs, masking in crowded settings and staying home if you’re sick.

“I think many of the things that we’ve learned over the last few years, I think, will help us to prevent the transmission any further, but we’re heading in the right direction. So that’s always a good sign,” she said.