Since first being detected in Newfoundland in 2021, a subtype of highly pathogenic avian influenza, HPAI A(H5Nx), has had a dramatic impact on North America.

The poultry industry has suffered the most, with almost 15 million birds dying or being culled to control the virus in Canada. The Supreme Court of Canada recently dismissed a British Columbia ostrich farm’s bid to stop a cull after avian flu was detected on the farm in December 2024.

The problem has been worse in the United States, with more than 180 million birds and over 1,000 dairy cattle farms being affected.

In the wild, the virus has also triggered mass die-offs of birds. In 2022 alone, at least 40,000 wild birds died of HPAI in eastern Canada, including 25,000 northern gannets and thousands of common murres and common eiders. Mortality due to HPAI has continued, with thousands of birds and many wild mammals being affected.

A(H5Nx) refers to avian influenza virus subtypes that share the H5 surface protein but differ in the N protein; current subtypes circulating in North America include H5N1 and H5N5.

As of yet there has been no evidence of sustained human-to-human transmission of the A(H5Nx) subtypes, leading the Public Health Agency of Canada to conclude that the most likely spread scenario now is

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