Genome sequence analysis of H5N1 influenza a virus isolated from a Vietnamese in 2007.

Highly pathogenic H5N1 avian influenza A virus (AIV) crossed the species barrier and caused a number of deaths in humans in Vietnam and 14 other countries. Since the last report of human H5N1 infection in November 2005, the first documented H5N1 human infection was reported in June 2007 in Vietnam and was followed by 7 more cases, including 5 fatalities. In this study, we isolated and analyzed the full length of the H5N1 genome from a sample from the first patient in 2007. Phylogenetic analysis of eight genomic segments of the H5N1 virus strain (A/Vietnam/HN/2007, VNH07) revealed that this strain appears to be of genotype V and contains the HA gene, which is classified into clade 2.3.4. The deduced amino acid sequence of the HA protein has a typical affinity sequence for α2,3 linkage (SAα2,3-Gal) receptors and typical multibasic cleavage sequences. Compared with other H5N1 isolates, VNH07 showed that the possible reassortments for the NA and NP segments occurred between A/goose/Guangxi/3017/2005-like isolates (2.3.2) and A/human/Zhejiang/16/2006-like isolates (2.3.4).