Epidemic influenza in Canada

Abstract

An extensive study has been made of the 1950 -51 influenza epidemic as it affected the Province of Ontario in Canada. Details of the haemagglutination- inhibition anti- body titres found amongst individuals of different age -groups prior to the onset of the epidemic have been presented. The antibody levels were determined for both Types A and B influenza virus and for two antigenic variants of Type A known as A -prime strains. The epidemic was followed both clinically and in the laboratory and the findings have been described. The opportunity occurred to observe outbreaks in a completely unprotected community and in a community partially protected by vaccination. The vaccine used contained all the strains employed in the earlier study of normal antibody titres. Altogether thirty -nine isolations of virus were made from all corners of Southern Ontario; thirty -seven of these strains were typed and identified as belonging to the A -prime sub- group.