Co-circulation of genetically distinct highly pathogenic avian influenza A clade 2.3.4.4 (H5N6) viruses in wild waterfowl and poultry in Europe and East Asia, 2017-18.

Marjolein J Poen,Mieke Steensels,Dennis De Meulder,Rachel D Scheuer,Anne Pohlmann,Martin Beer,Oanh Vuong,Thijs Kuiken,Mathilde Richard,Divya Venkatesh,Leon Kelder,Bas B Oude Munnink ,Marion Koopmans ,Ádám Dán ,Bénédicte Lambrecht ,Yong Joo Kim ,Youn‐Jeong Lee ,Theo M Bestebroer ,Ron A M Fouchier ,Vladimir Savić ,Ian H Brown ,Nicola S Lewis

doi:10.1093/ve/vez004

Abstract

Highly pathogenic avian influenza (HPAI) H5 clade 2.3.4.4 viruses were first introduced into Europe in late 2014 and re-introduced in late 2016, following detections in Asia and Russia. In contrast to the 2014–15 H5N8 wave, there was substantial local virus amplification in wild birds in Europe in 2016–17 and associated wild bird mortality, with evidence for occasional gene exchange with low pathogenic avian influenza (LPAI) viruses. Since December 2017, several European countries have again reported events or outbreaks with HPAI H5N6 reassortant viruses in both wild birds and poultry, respectively. Previous phylogenetic studies have shown that the two earliest incursions of HPAI H5N8 viruses originated in Southeast Asia and subsequently spread to Europe. In contrast, this study indicates that recent HPAI H5N6 viruses evolved from the H5N8 2016–17 viruses during 2017 by reassortment of a European HPAI H5N8 virus and wild host reservoir LPAI viruses. The genetic and phenotypic differences between these outbreaks and the continuing detections of HPAI viruses in Europe are a cause of concern for both animal and human health. The current co-circulation of potentially zoonotic HPAI and LPAI virus strains in Asia warrants the determination of drivers responsible for the global spread of Asian lineage viruses and the potential threat they pose to public health.

Highlights

Pathogenic avian influenza (HPAI) viruses cause outbreaks of disease, often resulting in mortality in poultry and wild bird species
Genetic analysis showed this Highly pathogenic avian influenza (HPAI) H5N6 virus to be a reassortant consisting of a clade 2.3.4.4 HA, an NA related to Chinese low pathogenic avian influenza (LPAI) H6N6 duck viruses, and an internal gene cassette closely related to 2011 HPAI H5 clade 2.3.2.1 viruses (FAO 2014; Bi et al 2016a,b)
New reassortant HPAI clade 2.3.4.4 Group B H5N6 viruses have been detected in both wild birds and poultry in several European and Asian countries from December 2017 onwards. Phylogenetic analyses of these viruses showed that they were related to the 2016–17 European HPAI H5N8 viruses, they were not the result of continued circulation of the single HPAI clade 2.3.4.4 Group B H5N6 virus that was detected in Greece in early 2017 during the 2016–17 clade 2.3.4.4 Group B H5N8 European outbreak

Summary

Introduction

Pathogenic avian influenza (HPAI) viruses cause outbreaks of disease, often resulting in mortality in poultry and wild bird species. Since 2003, HPAI H5 viruses of the A/Goose/ Guangdong/1/1996 (GsGd) lineage have been circulating enzootically in poultry in several countries in South and Southeast Asia, and Africa These HPAI H5 viruses have been introduced into wild birds with subsequent spread to other geographic areas, likely through bird migration (Verhagen, Herfst and Fouchier 2015; Lycett et al 2016). Viruses belonging to Group A emerged in late 2014 and spread to North America and Europe almost simultaneously After their initial detection, clade 2.3.4.4 Group B (H5N8) viruses were not detected in Southeast Asia until May 2016, when they were detected at Lake Uvs-Nur, Russia (Lee et al 2017a) and Qinghai lake, China (Li et al 2017). HPAI H5N6 viruses of clade 2.3.4.4 Group B, along with clade 2.3.4.4 Groups C and D have been detected in East Asian countries (Lee et al 2018a)

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