Multiple Sublineages of Influenza A Virus (H5N1), Vietnam, 2005−2007

Abstract

Phylogenetic analysis of influenza subtype H5N1 viruses isolated from Vietnam during 2005–2007 shows that multiple sublineages are present in Vietnam. Clade 2.3.4 viruses have replaced clade 1 viruses in northern Vietnam, and clade 1 viruses have been detected in southern Vietnam. Reassortment between these 2 sublineages has also occurred.

Keywords

• highly pathogenic avian influenza
• genotype Z
• Southeast Asia
• virus evolution
• molecular epidemiology
• dispatch