A firmly established H1N1 pandemic virus has killed more people in one week than through the entire spring, sending almost double the number of Canadians to intensive-care units.
Even more deaths are expected in the weeks to come as infection rates are higher this time around. And although health experts say the worst is possibly over, they take a cautious stance: Flu activity hasn't slowed down, and, in fact, is higher than in a normal seasonal influenza year.
In the second week of November alone, there were more people admitted to hospital (1,674) than during the April-August wave of the virus (1,473). More than 570 Canadians landed in intensive-care units this fall because of H1N1, double the number from the initial wave.
And deaths climbed from 35 in the first week of November to 84 the following week. In the initial wave back in the spring, 77 people died. More than 200 people have died from H1N1.
"What happens now? Who knows. Is it going to stay elevated for many more weeks or is it going to come down quite quickly? We don't know," said Michael Gardam, director of infectious diseases prevention and control at the Ontario Agency for Health Protection and Promotion.
"Part of that is going to be based on how much vaccine we roll out. The more people that are now immune to this, either because they've had it or because they've been vaccinated, the less fuel there is for the fire."
More than 12 million doses of the vaccine have been distributed to provinces and territories, and another 3 million will flow to jurisdictions this week as they open up flu clinics to healthy people.
In places like British Columbia, where the novel virus has clearly peaked, residents are still being encouraged to get the vaccine because H1N1 is still circulating. The majority of Canadians are still not protected from what is a relatively mild virus.
In the United States, 43 states are reporting activity, down from 46. But health officials there say that flu activity is more robust than it normally is for this time of the year.
"Influenza is unpredictable and it is so early in the year to have this much disease," Anne Schuchat of the U.S. Centers for Disease Control and Prevention said last week. "We don't know if these declines will persist, what the slope will be, whether we'll have a long decline or it will start to go up again."
Dr. Gardam echoed the sentiment, saying it remains a mystery as to whether the virus will drop off precipitously from its peak or take its time.
"We're still going to see the impact of this. There's still going to be people who end up in ICUs," he said. "If we keep going with a very aggressive vaccination campaign, I think it's reasonable to expect this peak could probably drop off quite quickly."
Regardless, health officials in Canada say the system is better prepared to handle the situation during the second wave.
Perry Kendall, B.C.'s provincial health officer, said that while more people are being admitted to hospital in the second wave, the cases are less severe.
"It could be due to faster access to [antiviral]drugs as we were better prepared in the second wave to rapidly treat the higher risk," Dr. Kendall said.
"Manitoba, for example, did not see a recurrence of serious illness and vented patients [those put on ventilators]among first nations in the second wave."