Molecular Characterization of Highly Pathogenic Avian Influenza Viruses H5N6 Detected in Denmark in 2018-2019.

Yuan Liang,Anders Gorm Pedersen,Charlotte Kristiane Hjulsager,Lars Erik Larsen,Pia Ryt-Hansen,Lise Kirstine Kvisgaard,Elisabeth Holm,Jesper Johannes Madsen,Pernille Dahl Nielsen,Kasper Thorup,Jesper Schak Krog,Anne Sofie Hammer

doi:10.3390/v13061052

Abstract

Beginning in late 2017, highly pathogenic avian influenza (HPAI) H5N6 viruses caused outbreaks in wild birds and poultry in several European countries. H5N6 viruses were detected in 43 wild birds found dead throughout Denmark. Most of the Danish virus-positive dead birds were found in the period from February to April 2018. However, unlike the rest of Europe, sporadic HPAI H5N6-positive dead wild birds were detected in Denmark in July, August, September, and December 2018, with the last positive bird being found in January 2019. HPAI viruses were not detected in active surveillance of apparently healthy wild birds. In this study, we use full genome sequencing and phylogenetic analysis to investigate the wild bird HPAI H5N6 viruses found in Denmark. The Danish viruses were found to be closely related to those of contemporary HPAI H5N6 viruses detected in Europe. Their sequences formed two clusters indicating that at least two or more introductions of H5N6 into Denmark occurred. Notably, all viruses detected in the latter half of 2018 and in 2019 grouped into the same cluster. The H5N6 viruses appeared to have been maintained undetected in the autumn 2018.

Highlights

Pathogenic avian influenza (HPAI) H5N1 virus (A/goose/Guangdong/1/96)was first detected in China [1] and has since evolved into clades 0–9 and multiple subclades [2]
At the end of 2017, several European countries were affected by Highly pathogenic avian influenza (HPAI) H5N6 outbreaks in wild birds and poultry
In April, detections were reported from Finland, Sweden, and Denmark in wild birds

Summary

Introduction

Pathogenic avian influenza (HPAI) H5N1 virus (A/goose/Guangdong/1/96)was first detected in China [1] and has since evolved into clades 0–9 and multiple subclades [2]. Clade 2.3.4.4 viruses have since 2014 been introduced into Europe on several occasions, where they have caused multiple outbreaks in wild birds and poultry [3,4,5,6,7,8,9]. From late 2017 and continuing into 2018, outbreaks in wild birds and poultry caused by HPAI H5N6 clade 2.3.4.4b viruses were reported in several European countries [16]. These viruses were reassortants of H5N8 clade 2.3.4.4b from 2016–2017 that contained polymerase basic protein 2 (PB2) and neuraminidase (NA) gene segments from European low pathogenic avian influenza (LPAI) viruses [4]. Phylogenetic analyses have shown that these viruses differed genetically from the other European HPAI

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