A study of acute respiratory disease in the community of Port Chalmers. II. Influenza A/Port Chalmers/1/73: intrafamilial spread and the effect of antibodies to the surface antigens.
During the first year of a study of respiratory disease in the semi-isolated community of Port Chalmers, New Zealand, an epidemic of clinical influenza occurred from which the variant influenza A/Port Chalmers/1/73 (H3N2) was isolated. Within a selected group of 26 families, 59 (46%) members had clinical or laboratory evidence of infection. During intrafamilial spread the infection frequency was highest for school-aged children (77%),  followed by female adults (67%), infants (64%) and male adults (41%). The index infection in each family was a school-age child on 10 occasions, suggesting the role of this age group in the transmission of influenza A in this community. The secondary attack rate (SAR) of 58.3% was higher than expected. In sera taken before the 1973 epidemic, 59% of family members had detectable HI antibody and 25% NI antibody to A/England/42/72 while 38% had detectable HI antibody and 8% NI antibody to A/Port Chalmers/1/73. The relation between pre-existing antibody and infection frequency is discussed.
D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral; D000956:Antigens, Viral; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks / Q000453:epidemiology*; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007223:Infant; D009980:Influenza A virus / Q000276:immunology; D007251:Influenza, Human / Q000453:epidemiology* / Q000276:immunology / Q000635:transmission; D008297:Male; D008875:Middle Aged; D009439:Neuraminidase / Q000276:immunology; D009520:New Zealand; D012140:Respiratory Tract Diseases / Q000453:epidemiology* / Q000276:immunology / Q000635:transmission
D000914:Antibodies, Viral; D000956:Antigens, Viral; D009439:Neuraminidase