The role of genetic and molecular characterization of viruses in relation to influenza surveillance and epidemiology: a WHO memorandum.

A number of recently developed analytical techniques have been used in many laboratories in attempts to define more fully the genetic and antigenic structures of influenza viruses. The applicability of some of these techniques and the value of the results obtained by their use are discussed in this Memorandum. The techniques considered range in complexity from comparative polyacrylamide gel electrophoresis of virus RNAs to determination of the nucleic acid sequences of the virus genes and the amino acid sequences of the corresponding proteins.