More than 15,000 Canadians were admitted to hospital for treatment of H1N1 influenza last winter - about three times the number of a "normal" flu season - a new analysis of hospital data reveals.
The pandemic flu, while far less deadly than feared, nonetheless strained hospitals, filling intensive-care units and doubling the number of emergency-room visits, according to findings from the Canadian Institute for Health Information.
"While there have been suggestions the response may have been exaggerated, our study shows that, in fact, the impact of the virus on hospitals was significant and much higher than originally estimated," said Jeremy Veillard, vice-president of research and analysis at CIHI.
"The good news is that Canada's acute-care facilities were able to weather the storm."
The strategies included moving patients from intensive care to regular wards with additional monitoring, purchasing ventilators, cancelling elective surgeries and bringing in additional staff.
Those measures were expensive. According to CIHI, caring for patients with H1N1 influenza cost hospitals more than $200-million, including $50-million in additional ER costs. Treatment, on average, cost $9,600 a patient.
Usually, several strains of influenza circulate during the winter season, but, last year, there was virtually no flu other than H1N1.
The new study shows that the bulk of hospital costs occurred in a five-week stretch in October-November, 2009, when H1N1 infections peaked. Two-thirds of flu-related hospital admissions happened in that period.
"The unanswered question is whether hospitals could have coped if the pandemic had lasted longer," said Kathleen Morris, head of emerging issues at CIHI.
During those five weeks, H1N1 accounted for 3.4 per cent of all hospital admissions. "In the world of hospitals, that is a really big number," Ms. Morris said. "The intensity is surprising."
The number of H1N1 patients exceeded those with common conditions such as heart attacks (2.5 per cent of hospital admissions) and strokes (1.6 per cent) during that peak period. Only childbirth accounted for more admissions (11.8 per cent).
Studies like this one are published so that health-care professionals and policy-makers can "use this information to adjust their pandemic plans," Ms. Morris said.
Globally, H1N1 killed 18,000, including 428 people in Canada. Those numbers, however, include only laboratory-confirmed cases, meaning that the actual toll of the disease was probably higher.
Between 2,000 and 8,000 Canadians die annually of influenza and its complications; most of them are elderly.
Earlier research showed that Canadians who died of H1N1 were, on average, 30 years younger than those who typically die of seasonal flu.
Infection with the pandemic strain of influenza also resulted in markedly more cases that required treatment in intensive-care units and resulted in patients requiring mechanical ventilation to breathe.
The Public Health Agency has yet to reveal the total cost of the response to the pandemic influenza, but it has said that estimates of $2-billion published in the media are exaggerated.
The largest single cost was the purchase of H1N1 vaccine, at about $400-million. What is unclear is how much it cost to administer the vaccine. About 11.6 million Canadians were vaccinated against H1N1.
In the new study, CIHI concludes that it is "unlikely the vaccine had a significant impact" on hospital admissions, in large part because the vaccine became available around the same time as admissions peaked.
Vaccination is under way for seasonal influenza; the shots are updated annually to account for circulating strains. This year's flu vaccine protects against influenza A/California/H1N1 (the official name for the pandemic strain), A/Perth/H3N2 and B/Brisbane.