Recent changes among human influenza viruses

Virus Res. 2004 Jul;103(1-2):47-52. doi: 10.1016/j.virusres.2004.02.011.


Recurrent epidemics of influenza are due to the frequent emergence of antigenic variants. With co-circulation of two influenza A subtypes and two antigenically distinct lineages of B viruses, genetic reassortment also has an important role in antigenic drift, as illustrated by recent changes in both A and B viruses. The H1N2 subtype viruses, which emerged during 2001, possessed a H1 HA similar to those of contemporary A/New Caledonia/20/99 (H1N1)-like viruses and seven genes closely related to those of recent H3N2 viruses, and did not represent a significant increase in the antigenic diversity of circulating viruses. The re-emergence of B/Victoria/2/87-lineage viruses, previously prevalent during the 1980s, in 2000 has been followed by the predominant circulation of reassortant B viruses possessing a B/Victoria-lineage HA and a B/Yamagata-lineage NA similar in sequence to those of recent B/Sichuan/379/99-like viruses. These events emphasize not only the lack of divergence in the complementary functional characteristics of the HA and NA of divergent influenza B lineages, but also the apparent convergence in compatibility between the H1 and N2 components of the two influenza A subtypes.

Publication types

  • Review

MeSH terms

  • Antigenic Variation*
  • Evolution, Molecular
  • Humans
  • Influenza A virus / classification
  • Influenza A virus / genetics*
  • Influenza B virus / classification
  • Influenza B virus / genetics*
  • Influenza, Human / epidemiology*
  • Influenza, Human / virology
  • Reassortant Viruses*