Iceland as Stepping Stone for Spread of Highly Pathogenic Avian Influenza Virus between Europe and North America

Abstract

Highly pathogenic avian influenza viruses (HPAIVs) of hemagglutinin type H5 and clade 2.3.4.4b have widely spread within the northern hemisphere since 2020 and threaten wild bird populations, as well as poultry production. We present phylogeographic evidence that Iceland has been used as a stepping stone for HPAIV translocation from northern Europe to North America by infected but mobile wild birds. At least 2 independent incursions of HPAIV H5N1 clade 2.3.4.4b assigned to 2 hemagglutinin clusters, B1 and B2, are documented for summer‒autumn 2021 and spring 2022. Spread of HPAIV H5N1 to and among colony-breeding pelagic avian species in Iceland is ongoing. Potentially devastating effects (i.e., local losses >25%) on these species caused by extended HPAIV circulation in space and time are being observed at several affected breeding sites throughout the North Atlantic.

No evidence for HPAI H5N1 2.3.4.4b incursion into Australia in 2022

“…5 Wild migratory waterfowl have been predominantly implicated in the re-occuring incursions into Europe and Africa. 6 However, there are few migratory waterfowl linking the Nearctic and Palearctic, as well as North and South America, suggesting that the long-distance dispersal of lineage 2.3.4.4b HPAI may rely on additional bird groups other than waterfowl (e.g., Günther et al 7 ). Lineage 2.3.4.4b has now been detected on all continents except Australia and Antarctica.…”

“…For Australia as for other regions in the world, HPAI incursion risk hinges on a combination of factors, including wild bird migration, virus pathogenicity in wild birds (notably whether wild birds are able to migrate while infected) and outbreaks and virus circulation in neighbouring regions (particularly at key stopover sites for migratory birds). That there was no incursion of HPAI in Australia in 2022 despite the arrival of millions of migratory birds, the capacity of wild birds to disperse this virus large distances (e.g., Caliendo et al 4 ), the apparent widening of the virus' host reservoir beyond waterfowl 7,8,14 and high levels of HPAI activity in Asian countries along the East Asian Australasian flyway 8 is unclear and warrants further investigation.…”

No evidence for HPAI H5N1 2.3.4.4b incursion into Australia in 2022

“…That there was no incursion of HPAI in Australia in 2022 despite the arrival of millions of migratory birds, the capacity of wild birds to disperse this virus large distances (e.g. (4)), the apparent widening of the virus’ host reservoir beyond waterfowl (7, 8, 14) and and high levels of HPAI activity in Asian countries along the East Asian Australasian flyway (8) is unclear and warrants further investigation.…”

“…However, there are few migratory waterfowl linking the Nearctic and Palearctic, as well as North and South America, suggesting that the long-distance dispersal of lineage 2.3.4.4b HPAI may rely on additional bird groups but waterfowl [e.g. (7)]. Lineage 2.3.4.4b has now been detected on all continents except Australia and Antarctica (8).…”

We need to keep an eye on avian influenza

“…A subclade of clade 2.3.4.4, namely 2.3.4.4b, now having an N1 NA again, started to spread extensively across Eurasia and Africa in 2020. Clade 2.3.4.4b viruses were then detected in North America early in 2022, where they arrived via migratory birds from Europe 8 ; they have now spread across the Americas. Similar to the situation in Eurasia and Africa, the clade 2.3.4.4b H5N1 virus is causing much damage to the poultry industry in North America and has devastated wild bird populations.…”