Abstract
OBJECTIVES: The annual influenza serosurvey was conducted to monitor influenza activity and gauge susceptibility to currently circulating and emerging influenza viruses. DESIGN: Six hundred and thirty sera from among specimens received for various tests were selected from all age groups and sent with age and geographic identifiers to the Laboratory Centre for Disease Control. Forty sera per province were selected during a one-week period beginning May 31, 1992 except for the province of Alberta which submitted 80 specimens, and Ontario and Quebec which each submitted 160 sera during a four-week period. Sera were tested for hemagglutination inhibiting (HI) antibodies against the 1992-93 vaccine strains and A/Taiwan/1/86 (H(1)N(1)). MAIN RESULTS: The percentage of sera from all ages having HI antibody to A/Beijing/353/89 (H(3)N(2)) at a titre of 1:40 or greater more than doubled from 22% in the 1991 sample to 53% in 1992. The percentage of sera in all ages having antibody titre at 1:40 or greater to H(1)N(1) strains A/Texas/36/91 and A/Taiwan/1/86 was 55% and 57%, respectively, in 1992, up from 45% with antibody titre 1:40 or greater to A/Taiwan/1/86 in 1991. Twenty-seven per cent of sera had antibody titre 1:40 or greater to B/Panama/45/90 compared with 19% in 1991. CONCLUSION: The relative increase in the percentage of sera with antibody with a titre of 1:40 or greater likely reflected vaccination efforts and the relative level of activity of the various influenza types and subtypes during the 1991-92 influenza season. The data also suggested that influenza B had the greatest potential for significant activity during the 1992-93 influenza season.