North Atlantic Migratory Bird Flyways Provide Routes for Intercontinental Movement of Avian Influenza Viruses

Abstract

Avian influenza virus (AIV) in wild birds has been of increasing interest over the last decade due to the emergence of AIVs that cause significant disease and mortality in both poultry and humans. While research clearly demonstrates that AIVs can move across the Pacific or Atlantic Ocean, there has been no data to support the mechanism of how this occurs. In spring and autumn of 2010 and autumn of 2011 we obtained cloacal swab samples from 1078 waterfowl, gulls, and shorebirds of various species in southwest and west Iceland and tested them for AIV. From these, we isolated and fully sequenced the genomes of 29 AIVs from wild caught gulls (Charadriiformes) and waterfowl (Anseriformes) in Iceland. We detected viruses that were entirely (8 of 8 genomic segments) of American lineage, viruses that were entirely of Eurasian lineage, and viruses with mixed American-Eurasian lineage. Prior to this work only 2 AIVs had been reported from wild birds in Iceland and only the sequence from one segment was available in GenBank. This is the first report of finding AIVs of entirely American lineage and Eurasian lineage, as well as reassortant viruses, together in the same geographic location. Our study demonstrates the importance of the North Atlantic as a corridor for the movement of AIVs between Europe and North America.

Spread and Persistence of Influenza A Viruses in Waterfowl Hosts in the North American Mississippi Migratory Flyway

“…This result is especially relevant for surveillance projects conducting surveillance for highly pathogenic strains in wild birds (74). Given the degree of reassortment in AIVs observed here, surveillance sites for strains of interest (e.g., HPH5N1, HPH7N3, and LPH7N9) are ideally situated within migratory routes, although gene segments from any one of these viruses may be found in other flyways (61,(75)(76)(77). While targeted surveillance efforts are necessary for rapid responses to disease threats, continued longitudinal studies examining the persistence and evolutionary patterns at regional sites are essential for elucidating the natural history of these viruses in their wild bird hosts (78,79).…”

“…The amount of reassortment suggests that it is unlikely that wild birds move entire AIV constellations from northern breeding grounds to wintering grounds (or vice versa in the next North American spring) during the course of a regular migratory season in the MMF. Instead, AIV gene segment dispersal by wild birds relies on rapid reassortment of constellations along the migratory flyway and, to a greater degree, among flyways (61). The observations of gene dispersal and limited persistence of gene lineages among flyways are likely the result of countless introductions and subsequent removals of single gene lineages introduced by reassortment to AIVs in other flyways (19).…”

Wild bird surveillance around outbreaks of highly pathogenic avian influenza A(H5N8) virus in the Netherlands, 2014, within the context of global flyways

“…These viruses can be carried over long distances along migratory flyways [3][4][5]. LPAI viruses of the H5 and H7 subtype can evolve into highly pathogenic avian influenza (HPAI) viruses upon introduction into poultry.…”

Intercontinental Spread of Asian-Origin H5N8 to North America through Beringia by Migratory Birds

“…In contrast, relatively few aquatic birds move from Asia to North America south of Alaska and relatively few from Alaska are associated with the Atlantic flyway, these being birds that winter in the eastern United States and come northwest in spring (17). Although the North Atlantic area is a potential route for migratory birds to transport avian influenza viruses between North America and Europe (18), the possibility of viral spread through the Atlantic rim was excluded on the basis of the timing of the detections and the very low level of viral gene flow between Pacific and Atlantic flyways (19) and because the icA H5 viruses identified in North America were genetically closer to East Asian viruses than to European viruses. Additionally, ongoing routine surveillance has detected no icA H5 virus in poultry or wild aquatic bird in the Atlantic flyway.…”