Abstract
This study aimed to elucidate virus, host and environmental dynamics of Vietnamese H5 highly pathogenic avian influenza viruses (HPAIVs) during 2014–2017. Epidemiologically, H5 HPAIVs were frequently detected in apparently healthy domestic and Muscovy ducks and therefore these are preferred species for H5 HPAIV detection in active surveillance. Virologically, clade 2.3.2.1c and 2.3.4.4 H5 HPAIVs were predominant and exhibited distinct phylogeographic evolution. Clade 2.3.2.1c viruses clustered phylogenetically in North, Central and South regions, whilst clade 2.3.4.4 viruses only detected in North and Central regions formed small groups. These viruses underwent diverse reassortment with existence of at least 12 genotypes and retained typical avian-specific motifs. These H5 HPAIVs exhibited large antigenic distance from progenitor viruses and commercial vaccines currently used in poultry. Bayesian phylodynamic analysis inferred that clade 2.3.2.1c viruses detected during 2014–2017 were likely descended from homologous clade viruses imported to Vietnam previously and/or preexisting Chinese viruses during 2012–2013. Vietnamese clade 2.3.4.4 viruses closely shared genetic traits with contemporary foreign spillovers, suggesting that there existed multiple transboundary virus dispersals to Vietnam. This study provides insights into the evolution of Vietnamese H5 HPAIVs and highlights the necessity of strengthening control measures such as, preventive surveillance and poultry vaccination.
Highlights
Www.nature.com/scientificreports thousand outbreaks in poultry[4,5]
Outbreaks of disease associated with H5 highly pathogenic avian influenza viruses (HPAIVs) were reported in all regions (North, Central and South) in each year, indicating that H5 HPAIVs persisted or occurred in a wide geographic and temporal range
The number of H5 HPAIV strains detected in each province that were available in public influenza virus databases were co-plotted in the choropleth map
Summary
Www.nature.com/scientificreports thousand outbreaks in poultry[4,5]. In addition, Gs/GD-lineage H5 HPAIVs have posed great public health concerns. The large genetic diversity of Vietnamese Gs/GD-lineage H5 HPAIVs is the result of multiple virus introductions and divergence of viruses circulating domestically[2,3]. After 2006, clade 1 H5 HPAIVs in the North and Central regions were replaced by other imported Gs/GD-lineage viruses such as clade 2.3.2 in 2005–2008 and 2.3.4 in 2007–2010. To reduce virus loads in poultry and human health risk, mass poultry vaccination against H5 HPAIVs was implemented in Vietnam in mid-200511,12. Though mass vaccination has been implemented, it was never anticipated that vaccination would eliminate Gs/GD-lineage H5 HPAIVs from Vietnam. Poultry vaccination accelerates selection of antigenic variants of H5 HPAIVs15. Novel strains of Gs/GD-lineage H5 HPAIVs that have a poor antigenic match with existing vaccines have been imported to Vietnam[2]. This study aimed to investigate virological and epidemiological features of contemporary Vietnamese H5 HPAIVs for the 2014–2017 period, using the results of our active surveillance, global surveillance data and longitudinal literature review
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