TORONTO - In some places it's surging, in others it's plateaued, and in other 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 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 predict what the final picture will look like. But it is fair to say this is an active year, flu-wise.
"I think we may have forgotten what real influenza feel 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 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 reporting that a lot of people are coming in sick with 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.
Flu season is characterized by a bolus of cases which, when plotted on a graph, looks like a steep curve. But in reality, one can catch the flu at any point in the year. Still, the concentration of cases at a point in the winter creates stress on health-care systems and the sensation that flu is all around.
King noted Ontario is seeing cases of invasive Streptococcus pneumoniae, which can be a complication of influenza and other respiratory viruses. One of the problems with flu is that it can domino into a bacterial pneumonia, and Strep pneumo, as it is called, is the most common of the bacterial pneumonias.
She suggested people who are vulnerable to the complications of flu — young children, people 65 and older, and people with chronic diseases, especially of the lungs and heart — should be vaccinated against influenza and pneumococcus. Flu shots are free for all in Ontario and pneumococcal vaccine is free in the province for anyone for whom it is recommended.
"We're in respiratory infectious disease season. We need to prevent flu, of course, through immunization. But we also need to make sure that people are appropriately immunized with pneumococcal vaccine as well," King said, adding that other respiratory viruses can also lead to pneumococcal pneumonia.
A spokesperson for Quebec's public health agency said flu activity in that province appears to have peaked over the Christmas holidays. While emergency rooms were busy, the agency did not receive reports of cancelled surgeries, Noemie Vanheuverzwijn said.
In Alberta, some hospitals have cancelled a few procedures. And many are reporting emergency rooms clogged with people with respiratory infections.
On Wednesday, Dr. Bill Dickout, medical director for Alberta Health Services' Edmonton zone, reminded people that in many cases flu can be managed at home, without medical care. People who are having trouble breathing or who are becoming dehydrated should seek help, he said.
Dr. Chris Sikora, medical officer of health for the Edmonton zone, said the numbers for the past couple of weeks suggest the flu season may have plateaued, but said he couldn't be sure.
In Manitoba, the chief provincial public health officer said the flu season there has been brisk. Visits to hospital emergency departments are definitely up, but hospitals haven't had to cancel surgeries, Dr. Michael Routledge said.
"The system's been able to cope with it, but it has been certainly busier than normal."
Routledge also noted the province has seen a lot of infections with respiratory syncytial virus or RSV, which can hit at any age but is particularly hard on children. Winnipeg's Children's Hospital has been stretched to cope with RSV cases, he said.
But Routledge put these respiratory disease developments in context. "This is the time of year for this to happen, so not uncommon at all."
"It's a busy flu season. It's busier than it has been for a couple of years. But I wouldn't call it out of the norm for what influenza can do in a given year."
Nationally, the Public Health Agency of Canada has learned of 15 deaths in people 20 and older so far this winter, said Dr. Barbara Raymond, the agency's director of pandemic preparedness planning.
At this point there have been no reported pediatric flu deaths in Canada this season. On average, one or two children a year die from flu in this country. But in the second half of December, 114 children were hospitalized because of influenza.