Transatlantic spread of highly pathogenic avian influenza H5N1 by wild birds from Europe to North America in 2021

Barnacle Geese by Edmund Fellowes

Author(s): Caliendo. V., Lewis, N.S., Pohlmann, A., Baillie, S.R., Banyard, A.C., Beer, M., Brown, I.H., Fouchier, R.A.M., Hansen, R.D.E., Lameris, T.K., Lang, A.S., Laurendaeu, S., Lung, O., Robertson, G., van der Jeugd, H., Alkie, T.N., Thorup, K., van Toor, M.L., Waldenstrom, J., Yason, C., Kuiken, T. & Berhane, Y.

Published: July 2022  

Journal: Scientific Reports Volume: 12

Article No.: 11729

Digital Identifier No. (DOI): /10.1038/s41598-022-13447-z

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Highly pathogenic avian influenza was detected in poultry and a free-living gull in Newfoundland and Labrador, Canada, in 2021, raising concerns about the potential for a new outbreak and questions about the likely origins of the virus.


Highly pathogenic avian influenza (HPAI) viruses of the A/Goose/Guangdong/1/1996 lineage (GsGd), which threaten the health of poultry, wildlife and humans, are spreading across Asia, Europe, Africa and North America but are currently absent from South America and Oceania. In December 2021, H5N1 HPAI viruses were detected in poultry and a free-living gull in St. John’s, Newfoundland and Labrador, Canada. Our phylogenetic analysis showed that these viruses were most closely related to HPAI GsGd viruses circulating in northwestern Europe in spring 2021. Our analysis of wild bird migration suggested that these viruses may have been carried across the Atlantic via Iceland, Greenland/Arctic or pelagic routes. The documented incursion of HPAI GsGd viruses into North America raises concern for further virus spread across the Americas by wild bird migration.

The discovery of highly pathogenic avian influenza (HPAI H5) in domestic birds at an exhibition farm on the island of Newfoundland, on Canada’s Atlantic coast, in December 2021 was the first report of HPAI H5 in the Americas since June 2015. Genetic analysis linked the virus from the farm, and a wild gull found elsehwere, to HPAI viruses circulating in Europe in spring 2021, suggesting that the virus had been carried across the Atlantic.

The study reported in this paper set out to investigate whether the HPAI cases in Newfoundland were linked to the recent (2020/2021) or currently ongoing (2021/2022) HPAI outbreaks in Europe, and to indicate the most likely scenario by which the virus crossed the Atlantic with migratory birds.

Phylogenetic analyses - which reveal the evolutionary relationships among species by comparing their genetic characteristics - enabled the researchers to explore the likely origins of the virus found in Canada. The virus from the Great Black-backed Gull was highly similar to that from birds at the exhibition farm, and both could be linked to European viruses circulating in early 2021, indicating a European origin. The researchers then turned to ring-recovery data from the EURING Migration Mapping Tool, which was developed by a partnership including BTO. These data suggested that the most likely route of transmission was either via the spring migration of bird species moving to Icelandic, Greenlandic or Canadian High Arctic breeding grounds from Europe, or migration directly across the Atlantic from Europe to North America

So why did the spread of HPAI across the Atlantic occur in the 2021/22 winter, but not before? There were unusually high rates of infection in European wild bird populations in late winter and spring 2021, including a higher proportion of Barnacle and Greylag Geese affected by HPAI in Europe from October 2020 (both species which migrate to Icelandic, Greenlandic or Canadian High Arctic breeding grounds in Spring). The study suggests that these two factors may explain why spread to Newfoundland happened during the 2021/2022 winter, and not in the previous winters.

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This research was (partly) financed by Horizon 2020 Framework Programme Deltaflu grant 727922 to VC, AP, MB, ACB, IHB, TK, MLT, JW, Horizon 2020 Framework Programme VEO grant 874735 to MB, RF, TK, German Federal Ministry of Education and Research ‘PREPMEDVET’grant 13N15449 to AP, UK Department for the Environment, Food and Rural Affairs (Defra) and the devolved Scottish and Welsh governments grants SV3032, SV3006 and SE2213 to ACB, RH, IHB, Emergency Funding of the Canadian Food Inspection and Environment and Climate Change Canada to YB, NIAID/NIH contract 75N93021C00014 to RF, Federal funds from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, under Contract No. 75N93021C00015 to NSL.
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