Influenza-attributable deaths, Canada 1990-1999.

The number of deaths attributable to influenza is believed to be considerably higher than the number certified by vital statistics registration as due to influenza. Weekly mortality data for Canada from the 1989/1990 to the 1998/1999 influenza seasons were analysed by cause of death, age group, and place of death to estimate the impact of influenza on mortality. A Poisson regression model was found to accurately predict all-cause, as well as cause-specific mortality, as a function of influenza-certified deaths, after controlling for seasonality, and trend. Influenza-attributable deaths were calculated as predicted less baseline-predicted deaths. In summary, throughout the 1990s there were on average just under 4000 deaths attributable to influenza annually (for an influenza-attributable mortality rate of 13/100,000 persons), varying from no detectable excess mortality for the 1990/1991 influenza season, to 6000-8000 influenza-attributable deaths for the more severe influenza seasons of 1997/1998 and 1998/1999. On average, 8% (95% CI 7-10) of influenza-attributable deaths were certified as influenza, although this percentage varied from 4% to 12% from year to year. Only 15% of the influenza-attributable deaths were certified as pneumonia, and for all respiratory causes, 40%. Deaths were distributed over most causes. The weekly pattern of influenza-certified deaths was a good predictor of excess all-cause mortality.

Characterization of Neisseria meningitidis strains isolated from invasive meningococcal disease cases in Canada in 2001.

With the recent introduction of polysaccharide-protein conjugated vaccines for the control of serogroup C meningococcal disease and the emergence of different variants of serogroup C meningococci, it is likely the epidemiology of meningococcal disease in many countries may be affected. We have therefore analysed and reported the characteristics of Neisseria meningitidis strains collected in 2001 from the Canadian surveillance program on invasive meningococcal disease. Only strains collected from normally sterile clinical sites of patients were studied. Of the 289 isolates obtained from individual patients, 173 (59.9%) were serogroup C, 76 (26.3%) were serogroup B, 30 (10.4%) were serogroup Y, and 10 (3.5%) were serogroup W135. Ninety-six percent of the serogroup C isolates belonged to the ET-15 clone, with an additional 2.3% belonging to other electrophoretic types within the ET-37 clonal complex. Different antigenic variants of the endemic serogroup C ET-15 clone were responsible for localized outbreaks in different parts of the country. One novel variant with the antigenic composition of C:2a:P1.1,7 was reported in two provinces, Quebec and Ontario. Eighteen percent of the meningococci isolated from patients in Ontario belonged to serogroup Y, compared with only 8% in the rest of Canada. The current data highlight the importance of strain characterization by serogroup, serotype, and serosubtype antigens in providing useful information for the surveillance of meningococcal disease in Canada.