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.

In December 2019, a novel coronavirus of likely zoonotic origin, SARS-CoV-2, was discovered following detection of an outbreak of acute respiratory disease in people from Wuhan, China (Zhou et al., 2020). The virus has since spread across the world and in early March 2020 the WHO declared COVID-19, the disease caused by the virus, a pandemic (https://www.who.int/dg/speec hes/detai l/who-direc tor-gener al-s-openi ng-remar ks-at-the-media -brief ing-on-covid -19---11-march -2020). As of November 2020, worldwide mortality from COVID-19 was over 1,360,000 deaths (https://coron avirus.jhu.edu/map.html; Accessed November 20, 2020).Coronaviruses have large (~30 kb), positive-sense, RNA genomes and are known to infect a variety of mammals and birds. Their genomes are also known to have a high propensity for recombination with other coronaviruses. Coronaviruses are classified as alpha-, beta-, gamma-or deltacoronaviruses. Both alpha-and betacoronaviruses infect mammals, and while worldwide bats are known to be infected by both types of viruses (Decaro & Larusso, 2020; Falcon et al., 2011), only alphacoronaviruses have been found to date in North American bats (Olival et al., 2020).

Highly pathogenic clade 2.3.4.4 H5N8, H5N2, and H5N1 influenza A viruses were first detected in wild, captive, and domestic birds in North America in November-December 2014. In this study, we used wild waterbird samples collected in Alaska prior to the initial detection of clade 2.3.4.4 H5 influenza A viruses in North America to assess the evidence for: (1) dispersal of highly pathogenic influenza A viruses from East Asia to North America by migratory birds via Alaska and (2) ancestral origins of clade 2.3.4.4 H5 reassortant viruses in Beringia. Although we did not detect highly pathogenic influenza A viruses in our sample collection from western Alaska, we did identify viruses that contained gene segments sharing recent common ancestry with intercontinental reassortant H5N2 and H5N1 viruses. Results of phylogenetic analyses and estimates for times of most recent common ancestry support migratory birds sampled in Beringia as maintaining viral diversity closely related to novel highly pathogenic influenza A virus genotypes detected in North America. Although our results do not elucidate the route by which highly pathogenic influenza A viruses were introduced into North America, genetic evidence is consistent with the hypothesized trans-Beringian route of introduction via migratory birds.