Flu season has arrived early in Ontario, with hospitals reporting an influx of patients with the illness and doctors reminding citizens that it's not too late to get the flu vaccine.

Across the provinces, a number of health units are extending their flu vaccine clinics, hoping to inoculate those who thought they'd skip the shot this year but are now re-thinking that.

The indications are that this year's dominant flu strain -- H3N2 -- is not causing more severe disease that previous flu seasons (with the exception of the 2009/10 H1N1 pandemic strain). The problem is that not enough people have been vaccinated.

Dr. David Williams, Ontario's associate chief medical officer of health, told reporters Thursday that it appears public health officials failed to get the message out that vaccination is just as necessary as ever.

"Part of the problem is that people have been less than vigilant about getting out and getting the flu shot, including those who are at high risk," he said.

Williams notes that as of Jan. 8, Ontario has seen a surge of more than 8,700 new cases of influenza reported.

In the last week, there were more than 700 lab-confirmed influenza cases. That compares to the 100 or so cases the province has seen around the same time in previous seasons.

Dr. Neil Rau, a microbiologist in Oakville, Ont., said this year is shaping up to be "no worse than 2008" and said many of the flu cases have centred around a small area of Toronto.

"There are always local variations with flu," he said. "I don't think it describes what all of Canada is seeing so far or what the U.S. is seeing and rest of the world is seeing."

Williams noted that H3N2 is quite different from H1N1, the strain that dominated last year. Those who were either vaccinated against that strain or who became infected by it are not protected against this year's flu.

"Unlike the H1N1, where we found a lot of people born pre-1957 had some immunity, those people do not have immunity to this and they are very susceptible to the complications," Williams said.

He says there remains a misconception that the flu is much like a bad cold.

"Influenza A is not like that. People who get it are much more ill, especially healthy people. They're often out of it for five to seven days. It's like getting hit with a Mack truck," he said.

"It's something not to be taken lightly."

Williams encouraged Ontarians to get the vaccines as soon as possible, because it takes seven to 10 days for the vaccine to confer immunity, and it's still possible to become infected during that time.

Ontario Minister of Health Deb Matthews said vaccination rates in the province are lower than usual and that's leading to an increased demand on the health-care system. The surge in flu cases has clogged hospital emergency rooms and may begin to postpone elective surgeries.

"I'm here to ask the people of Ontario to get their flu shot," Matthews said.

"There's really no reason not to do it."