2nd H1N1 wave in Canada larger than 1st
The second wave of the H1N1 pandemic was substantially greater than the first in terms of hospital admissions, deaths and intensive care cases, according to a Canadian study.
Since more people were hospitalized during the second wave compared to the first, the percentage of people with severe outcomes was smaller, says the study in Monday's issue of the Canadian Medical Association Journal.
Although the patients admitted to hospital were older and more of them had underlying conditions, a smaller proportion had a severe outcome.
During the first wave from last April to June 20, 2009, Nunavut, Manitoba and Quebec had the highest rates for hospital admissions.
In the second wave, all provinces and territories were affected, with the Maritime provinces, Alberta, British Columbia, Yukon and the Northwest Territories experiencing much higher rates of hospital admission than in the first one.
Quebec and Ontario were impacted in both waves, with Quebec reporting the highest number of hospitalizations and Ontario reporting the most deaths overall.
At the height of the first wave from May 31 to June 20, 2009, 9.4 per cent of hospital admissions, 10 per cent of admissions to intensive care admissions (ICU) and 10 per cent of deaths occurred.
At the height of the second wave from Oct. 25 to Nov. 14, 2009, 51 per cent of overall hospital admissions, 49 per cent of ICU admissions and 53 per cent of deaths occurred.
"The second wave was substantially larger and, although the patients admitted to hospital were older and more of them had underlying conditions, a smaller proportion had a severe outcome," wrote Melissa Helferty of the Public Health Agency of Canada and her co-authors.
Helferty's colleague and co-author, Dr. John Spika, director general of the Centre for Immunization and Respiratory Infectious Diseases at PHAC, attributed the difference to more promotion of early antiviral treatment for those in high-risk groups and availability of the vaccine.
"The authors interpret the improved outcomes in the second wave with public health interventions [vaccination] and this does go along with estimates from Ontario that the H1N1 vaccination program was worth the money," Dr. Fiona Smaill, an infectious diseases expert at McMaster University in Hamilton, Ont., said in an email to The Canadian Press.
With files from The Canadian Press