Abstract
We report 15 new avian influenza virus A/H5N1 haemagglutinin (HA) sequences sampled from visibly sick domestic poultry in southern Vietnam, between 1 January 2010 and 6 March 2010. These HA sequences form a new sub-clade of the clade 1 H5N1 viruses that have been circulating in Vietnam since 2003/2004. The viruses are characterized by a change from isoleucine to valine at position 514 (I514V) and are 1.8% divergent at the nucleotide level from HA sequences sampled in Vietnam in 2007. Five new amino acid changes were observed at previously identified antigenic sites, and three were located within structural elements of the receptor-binding domain. One new mutation removed a potential N-linked glycosylation site, and a methionine insertion was observed in one virus at the polybasic cleavage site. Five of these viruses were sampled from farms where poultry were vaccinated against H5N1, but there was no association between observed amino acid changes and flock vaccination status. Despite the current lack of evidence for antigenic drift or immune escape in Vietnamese H5N1 viruses, continued surveillance remains a high priority.
Highlights
Over 500 human cases of H5N1 influenza virus infection have been recorded since the emergence of this highly pathogenic virus subtype in 1996/1997 (Peiris et al, 2007; Tarantola et al, 2010)
The majority of human cases have occurred in three countries, Indonesia (174), Egypt (130) and Vietnam (119); all of which have high rates of household poultry ownership, a large network of markets with high levels of poultry sales and consumption (Domenech et al, 2009) and frequent outbreaks and high prevalence of highly pathogenic avian influenza (HPAI) in domestic poultry
We sequenced the HA of H5N1 viruses obtained from diseased domestic poultry during passive surveillance activities of January–March 2010 in four provinces of southern Vietnam: Khanh Hoa, Ben Tre, Soc Trang and Ca Mau
Summary
Over 500 human cases of H5N1 influenza virus infection have been recorded since the emergence of this highly pathogenic virus subtype in 1996/1997 (Peiris et al, 2007; Tarantola et al, 2010). The global incidence of human H5N1 cases has declined recently, surveillance and molecular characterization of highly pathogenic avian influenza (HPAI) viruses remain a high priority. The majority of human cases have occurred in three countries, Indonesia (174), Egypt (130) and Vietnam (119); all of which have high rates of household poultry ownership, a large network of markets with high levels of poultry sales and consumption (Domenech et al, 2009) and frequent outbreaks and high prevalence of HPAI in domestic poultry. H5N1 avian influenza has been a constant threat as a potentially fatal zoonotic infection, causing regular outbreaks between December and February
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