Emergence of Influenza A H1N2 Reassortant Viruses in the Human Population during 2001

Abstract

Influenza A H1N2 viruses, which emerged during 2001, are genetic reassortants between H1N1 and H3N2 subtype viruses which have cocirculated in the human population since 1977. They possess a H1 hemagglutinin antigenically and genetically similar to contemporary A/New Caledonia/20/99 (H1N1)-like viruses and seven genes closely related to those of recent A/Moscow/10/99 (H3N2)-like viruses. The viruses have spread to many regions of the world and have predominated over H1N1 viruses in several countries. Since half of the amino acid changes which accumulated in the HAs of H1N1 viruses since 1995 are in residues implicated in receptor binding, functional changes in the H1 HA may have facilitated its replacement of the H3 HA and may contribute to the future epidemiologic significance of these H1N2 viruses.

Genetic Analysis of Influenza A/H3N2 and A/H1N1 Viruses Circulating in Vietnam from 2001 to 2006

“…The HA gene of the virus was closely related to those in group III, which were antigenically related to the A/New Caledonia/20/99-like strain, but the NA and M genes were closely related to the A/Solomon Islands/3/06 strain. An intersubtype reassortant, A/H1N2, was isolated from Japan as well as from many other areas (13,19,32,42) after 2001, but this was not detected in our present analysis.…”

Virulence determinants of pandemic influenza viruses

“…After 1977, the reemerged H1N1 virus began to cocirculate with the H3N2 viruses that were present at the time and continues to do so today (39). Notably, there has been reassortment between the two cocirculating strains, generating an H1N2 virus first isolated in the 2001-2002 influenza season (40). These H1N2 viruses failed to cause appreciable disease and did not persist in subsequent influenza seasons (41).…”

Virological surveillance in Africa can contribute to early detection of new genetic and antigenic lineages of influenza viruses

“…Rates of infection are highest among children, but severe illness and death from influenza are greater among the elderly and people with chronic medical conditions that place them at greater risk for influenza complications [1]. Current human influenza viruses (IV) belong to the subtypes A(H1N1) and A(H3N2), and between 2001 and 2005 subtype A(H1N2) viruses have been circulating widely [2][3]. Influenza B viruses are subdivided into the B/Victoria and B/Yamagata lineages [4][5].…”