Packed emergency wards, filled with feverish, coughing people suffering from the flu. It is a scene being played out at hospitals across the country.

This flu season started a bit earlier than normal and is now moving into high gear, experts say.

That certainly seemed clear at Humber River Hospital in Toronto on Boxing Day.

"We saw 510 people come through our emergency room department and our after-hours kids clinic on that day," said Dr. Tasleem Nimjee, an ER physician at the hospital.

What may also be a bit unusual is the presence of both flu strains at the same time. Influenza A mainly affects older people, while influenza B typically targets children and youth. Normally, one strain wanes as the other peaks.

Every year, the flu kills an estimated 3,000 Canadians, often young children, the elderly and those with pre-existing medical conditions such as asthma.

So far, there have been nearly 12,500 confirmed cases of flu across Canada and 10 deaths.

In Manitoba, two families are reeling from the recent deaths of their loved ones. Joanne Ens, 24, died from a bacterial infection after battling the flu for several days, while Blaine Ruppenthal, 17, also died of complications from the flu.

It's that toll on the body exacted by the flu that worries doctors.

"The flu can complicate pre-existing heart disease, asthma, chronic lung disease, quite often it causes pneumonia and that's sort of its route of causation. It's what makes people really sick," said Dr. Mark Loeb, division director for infectious diseases at McMaster University in Hamilton.

WATCH | Q&A: Chief Public Health Officer of Canada Dr. Theresa Tam answered your questions about the flu

Canada's flu season started a bit earlier than normal and is now moving into high gear, experts say. CBC's Carole MacNeil and Chief Public Health Officer of Canada Dr. Theresa Tam take audience questions about the flu. 17:36

In Ajax, Ont., about 50 kilometres east of Toronto, Wendy Wilson is recovering from a bout of pneumonia that left her with a cracked rib. It started with a sore throat and flu-like symptoms.

"I was afraid to walk fast or move too fast because it was like all of a sudden, I'd start coughing, and I'm feeling like I can't catch my breath," she said.

"It was shocking because it came so quick."

And those symptoms can sometimes worsen, Nimjee said.

"If somebody is really short of breath and not able to manage without assisted support, without oxygen or hydration or need antibiotics through an IV, those would be the people who would be admitted to hospital," she said.

Ascend the mountain

Yet experts say it's still too early to gauge the severity of this particular flu season. While doctors at the U.S. Centers for Disease Control and Prevention point to ominous signs, such as widespread flu activity and hospitalizations, as indicators of a bad year, Canadian numbers, so far, don't bear that out.

Dr. Tasleem Nimjee, an emergency room physician at Humber River Hospital in Toronto, says the ER and after-hours kids clinic have been very busy. (Craig Chivers/CBC)

"Based on data up to January 4, 2020, the Public Health Agency of Canada would not characterize the current flu season as severe at this time," officials told CBC News in an emailed response to questions.

Loeb agreed it's too early to tell. Typically, flu season runs from mid-November until April.

"Flu epidemics are like a mountain. It's like an ascension and then you reach a peak and then you descend. Now we're on the ascension of that mountain and we don't know exactly where it will peak."

However, doctors agree on one thing: get the flu shot.

Although this year's vaccine may not be a perfect match to the current strains, some protection is always better than none, according to Loeb.

"Sometimes prevention is harder for people to understand than treatment."