Antigenic heterogeneity among influenza A(H3N2) field isolates during an outbreak in 1982/83, estimated by methods of numerical taxonomy.

Fourteen influenza A(H3N2) field isolates, mainly obtained during the first weeks of the 1982/83 influenza epidemic in The Netherlands, and nine influenza A(H3N2) reference strains were examined by means of haemagglutination inhibition (HI) tests with 23 polyclonal ferret sera. The resulting HI patterns were subjected to various methods of numerical taxonomy using, among others, taxonomic distance and correlation between strains for resemblance coefficients. Marked differences between distance and correlation coefficients were found in strains which differed in avidity only. The field isolates could be divided into four groups in respect of their taxonomic resemblance to the reference strains. The same grouping was found for five of the field isolates by testing these against 200 human sera.