Vials of flu vaccine are displayed at the Whittier Street Health Center in Boston, Mass., Wednesday, Jan. 9, 2013. (AP Photo/Charles Krupa)

TORONTO - In some places it's surging, in others it's plateaued and in some parts of the country, it may actually be on the wane.

But in most parts of Canada this winter, influenza has been reminding Canadians what a real flu season feels like.

Emergency departments in parts of the country are reporting heavy traffic. Some hospitals have cut back on surgeries. Sales of antiviral drugs have been strong enough to create the possibility of a shortage, prompting the federal government to lend stores of Tamiflu from the national emergency drug stockpile back to the manufacturer, Roche Canada.

After a couple of years of ho-hum flu seasons, some people may be tempted to cast this year as the worst in a decade. This early in the winter it's too soon to say what the final picture will look like. But it is fair to say that this is an active year, flu-wise.

"I think we may have forgotten what real influenza feels like, because for whatever reasons in the post-pandemic period, for us anyway in B.C. the seasons have been quite mild," Dr. Danuta Skowronski, a flu expert at the BC Centre for Disease Control, said Wednesday.

"This season is more like what we expect from an influenza A — H3 in particular — season."

Skowronski was referring to the fact that much of the illness this year in Canada is being caused by the influenza A virus H3N2. (Flu viruses that infect humans are mainly from either from the influenza A or B family. There are two subtypes of A viruses — H3N2 and H1N1.)

Winters when H3N2 viruses predominate are generally harder flu seasons because this subtype hits the elderly with particular severity.

In Ontario, a surveillance system that monitors, in real time, the emergency rooms of 72 hospitals around the province is showing a lot of activity for respiratory viruses, said Dr. Arlene King, the province's chief medical officer of health.

King said Ontario is probably six weeks into what is typically an eight-week cycle of influenza, so flu activity may actually be starting to slow.

While flu season is characterized by a bolus of cases that when plotted on a graph looks like a steep curve, one can catch the flu at any point in the year. Still, the concentration of cases in the winter creates stress on health-care systems and the sensation that flu is all around.

News from © The Canadian Press, 2013