Intercontinental Movement of Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4 Virus to the United States, 2021

Abstract

We detected Eurasian-origin highly pathogenic avian influenza A(H5N1) virus belonging to the Gs/GD lineage, clade 2.3.4.4b, in wild waterfowl in 2 Atlantic coastal states in the United States. Bird banding data showed widespread movement of waterfowl within the Atlantic Flyway and between neighboring flyways and northern breeding grounds.

Keywords: United States; clade 2.3.4.4; dispersal; highly pathogenic avian influenza A(H5N1) virus; influenza; influenza viruses; intercontinental movement; respiratory infections; viruses; wild birds; zoonoses.

Figure 1

Maximum-likelihood phylogenic analysis of the hemagglutinin gene segment of the first sequenced set of wild bird isolates of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4 virus, United States, 2021. Red indicates US wild bird highly pathogenic detections, and blue indicates closest virus detected in Newfoundland, Canada. MAFFT alignment and RAxML trees were generated in Geneious 11.1.5 (https://www.geneious.com) and visualized in FigTree 1.4.1 (https://tree.bio.ed.ac.uk). Scale bar indicates average nucleotide substitutions per site.

Figure 2

Dabbling duck movements to and from North Carolina and South Carolina, USA, to and from other states or provinces in study of highly pathogenic avian influenza A(H5N1) 2.3.4.4 virus, United States, 2021. Data are based on North American Bird Banding Program data collected during 1960–2021. Color intensities represent number of movements detected between a given state or province and North Carolina or South Carolina. Lines are positioned at the centroid of a given state or province. Bold border lines indicate administrative migratory bird flyways (from west to east: Pacific Flyway, Central Flyway, Mississippi Flyway, and Atlantic Flyway).