Simultaneous introductions of HPAI viruses into Canada across two intercontinental flyways
In December 2021, H5N1 HPAI viruses from the 2.3.4.4b clade, genetically related to viruses circulating in Europe in early 2021, were isolated from poultry as well as a Great Black-backed Gull (Laurus Marinus) in Newfoundland, Canada. In the USA, the H5N1 HPAI viruses were isolated from wild waterfowl from two Atlantic coastal states, coinciding with the movement of banded birds within the Atlantic flyway. Wild bird migration that occurred via the Arctic may have carried these viruses from Europe across the Atlantic to Canada.
In Japan, particularly in the Hokkaido region, in January 2022 the presence of an H5N1 HPAI virus was identified in a White-tailed Eagle (Haliaeetus albicilla). In February 2022, Canada reported H5N1 viruses from a Bald Eagle (Haliaeetus leucocephalus) and in April 2022 from a commercial chicken flock, both in British Columbia.
A new study, demonstrates the presence of two ancestrally and genetically different GsGd lineage H5N1 HPAI clade 2.3.4.4b viruses isolated from domestic chickens and Bald Eagle in British Columbia in 2022. This work revealed the current outbreak viruses in British Columbia were linked with viruses circulating in Asia, Europe, West Africa and the ongoing expansion of H5N1 HPAI viruses from parts of Canada and the USA. The two viruses, although identified from the same province, are distinct based on phylogenetic reconstruction, suggesting they might have different incursion routes. The genetic footprints of all segments of the viruses, integrating migratory wild bird flyways and our phylogenetic data, provide evidence that the H5N1 HPAI viruses have been introduced to British Columbia likely through two prominent flyways - the East Asia Australasia/Pacific and the Atlantic flyways.
In the current study, we demonstrate the presence of two ancestrally and genetically different GsGd lineage H5N1 HPAI clade 2.3.4.4b viruses isolated from domestic chickens and Bald Eagle in British Columbia in 2022. This work revealed the current outbreak viruses in British Columbia were linked with viruses circulating in Asia, Europe, West Africa, and the ongoing expansion of H5N1 HPAI viruses from parts of Canada and the USA.
The virus from the Bald Eagle identified in British Columbia in February 2022 has no evidence of epidemiological connection with the virus identified in chickens from the same province in April 2022. The two viruses, although identified from the same province, are distinct based on phylogenetic reconstruction, suggesting they might have different incursion routes. The H5N1 HPAI virus isolated from the Bald Eagle is placed with a virus isolated from a White-tailed Eagle from Japan in 2022 and importantly, distinct from the Newfoundland H5N1 HPAI viruses. The genetic footprints of all segments of the viruses, provide evidence that the H5N1 HPAI viruses have been introduced to British Columbia likely through two prominent flyways - the East Asia Australasia/Pacific and the Atlantic flyways.
