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While HPAI H5 no longer completely retreats each summer, the warmer months of the year usually see far less activity than the fall and winter. And each fall, as we await the arrival of the annual southbound migration of birds, we ponder what changes that might bring (see H5Nx: Reassort & Repeat).
In the 2023-2024 avian flu season, we famously saw the emergence of a `bovine' H5N1 genotype B3.13, which has since infected (at least) 1,179 cattle herds across 20 states.
Avian flu's return in the fall of 2024 brought with it a far more aggressive poultry/wild bird strain (D1.1) (which can also infects humans), along with a spate of oseltamivir resistant outbreaks in Canada.
Last fall - while both D1.1 and B3.13 continued to dominate - we saw the first known human infection with HPAI H5N5 in a backyard bird keeper in Washington State.
While each fall doesn't guarantee a new wrinkle in the avian flu story, we often first notice big changes in the makeup and behavior of avian flu when migratory birds return from their high latitude roosting spots (see Sci Repts.: Southward Autumn Migration Of Waterfowl Facilitates Transmission Of HPAI H5N1).
We've already witnessed a noticeable uptick in outbreaks in commercial and backyard poultry in the United States over the past couple of weeks (see USDA dashboard below).
To this we can add Canada's first poultry outbreak since May 16th, a poultry farm in the rural municipality of De Salaberry, in Manitoba.
Whether this fall brings anything substantially different remains to be seen, and unfortunately, we probably won't learn about any genetic changes for several months. As we saw last year, in Nature: Lengthy Delays in H5N1 Genome Submissions to GISAID, the average delay in submitting sequences to GISAID was 7 months (228 days), with some countries taking nearly 2 years.Canada's first poultry outbreak of the new season comes at roughly the same time as last year (Sept 9th), and considerably earlier than the first Canadian outbreak of fall 2024 (Oct 21st).
And genetic sequences - even when they are submitted to GISAID - are often devoid of crucial metadata (i.e. collection date, exact location, host-specific information, etc.), limiting their value to the scientific community.
For now, we'll have to content ourselves with less specific data; where, when, the size, and the type of outbreak (commercial poultry, backyard flocks, livestock, peridomestic mammals, or even humans).
In the meantime, if you raise backyard birds, or frequent live markets, now is a good time to familiarize yourselves with the risks of avian flu, and the things you can do to reduce those risks.
UF/IFAS Extension: What Backyard Flock Owners Need to Know about Bird Flu (Influenza H5N1)
