This year’s flu season may have gotten off to a slow, late start, but doctors’ offices and hospitals are now starting to see a surge in infections.

According to the Public Health Agency of Canada’s FluWatch program, the number of flu cases have been rising steadily over the last weeks, ramping up toward peak levels.

That means this year's season could run late into the spring, says Dr. Allison McGeer, the director of Infection Control at Toronto’s Mount Sinai Hospital.

“Normally, influenza activity is substantially down by the end of March. This year, it’s probably going to extend into April,” she told

“…I’m betting on mid to late April before it’s over.”

The late start means patients can expect crowded hospital emergency departments and doctors’ offices over the next few weeks.

In Saskatchewan, two of Saskatoon's three major hospitals reported this week they are overwhelmed and in a "critical overcapacity situation," because an increase in flu is putting stress on the system.

While one might assume that this year’s milder-than-normal winter is the reason behind the late arrival of the flu, McGeer says that’s not necessarily so. Influenza arrives in waves and each year is different from the last.

“Flu does what it likes. The season starts when flu viruses decide that the flu season will start. It’s just not something we can predict,” she said.

The good news, though, is that this year’s season is turning out to be a mild one, with fewer hospitalizations and severe illnesses.

Last year’s flu season was particularly severe and led to more than 6,700 hospitalizations and 590 flu-related deaths. This year so far, there have been only 617 hospitalizations and 22 deaths..

McGeer says that’s in part because last year, the dominant strain was H3N2, which tends to affect seniors harder than others and leads to more hospitalizations.

This year, the dominant strain is H1N1, or swine flu, which isn’t as hard on seniors because of previous immunity, but is harder on young children.

“So we won’t see as many older people with flu this year as in other years, but we will see more pregnant women with flu and more kids with flu,” she said.

Another bit of good news is that the flu vaccine is generally very effective at preventing H1N1.

“That means vaccine efficacy will definitely be good this year. And it’s looking pretty good against H3N2 as well,” she said.

U.S. health authorities are already reporting that this year’s vaccine is doing a good job at preventing infections. It's been a milder flu season south of the border, though the season has not yet peaked there either.

As for those who still haven’t gotten the flu shot, McGeer says the further we get into the season, the less benefit one can expect from the vaccine. But if you have a small child at home or have close contact with an immune-compromised senior or someone undergoing chemotherapy, you might still want to get it.

And if you were diligent enough to get the vaccine early, in October, there’s no reason to worry you won’t stay protected if the season runs late.

“If you had your flu shot, you don’t need to worry about it running out before the end of the season,” McGeer said.