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Although the spillover of HPAI H5N1 into mammals has most of our attention, H5 influenza continues to evolve, and over the years has produced dozens of clades and subclades, hundreds of genotypes, spanning 9 different subtypes (H5N1-H5N9).
Many have failed to thrive, or gone extinct, but new variations continue to appear.
While China's H5N6 virus is arguably the most concerning of these offshoots, we've also been following the spread of HPAI H5N5 in Europe - and its crossing over into Canada - with considerable interest.
We've seen reports of H5N5 in European birds going back to 2016, but it was detected in dead raccoons on Prince Edward Island about 18 months ago (see CIDRAP Report Canada reports first H5N5 avian flu in a mammal).We looked in again last April with HPAI H5N5: A Variation On A Theme, and again in May with WAHIS: More Reports of HPAI H5N5 in Canada.
Last July, in Cell Reports: Multiple Transatlantic Incursions of HPAI clade 2.3.4.4b A(H5N5) Virus into North America and Spillover to Mammals, researchers reported finding the mammalian adaptive E627K mutation in a number of samples. They wrote:
The UK, which last reported an outbreak of HPAI in poultry last February, yesterday published 3 avian flu related documents in rapid succession.Thus, while A(H5N5) viruses are comparably uncommon, their high virulence and mortality potential demand global surveillance and further studies to untangle the molecular markers influencing virulence, transmission, adaptability, and host susceptibility.
Since our previous outbreak assessment on 7 October 2024, there have been no new reports of high pathogenicity avian influenza (HPAI) H5 clade 2.3.3.4b in domestic poultry in Great Britain (England, Scotland and Wales). There have, however, been 15 more HPAI H5 clade 2.3.3.4b events involving 26 “found-dead” wild birds in Great Britain. Of these, 25 were HPAI H5N5 with 1 case of HPAI H5N1.
Second, a Bird flu (avian influenza): latest situation in England update which stated, based on the recent findings in wild birds, that the `. . . risk level of HPAI H5 in wild birds has increased from medium to high.'
5 November 2024
And lastly, overnight, Defra announced the detection of HPAI H5N5 at a poultry farm in Yorkshire.All bird keepers are urged to remain vigilant and take action to protect their birds following a further increase in the avian influenza (‘bird flu’) risk levels in Great Britain.
Highly pathogenic avian influenza (HPAI) H5N5 and H5N1 have been detected in wild birds in Great Britain this autumn.
The risk level of HPAI H5 in wild birds has increased from medium to high.
The risk level in poultry:
- where good biosecurity is consistently applied at all times has increased from very low to low with low uncertainty
- where there is suboptimal or poor biosecurity remains assessed as low but is heightened with high uncertainty
While findings of HPAI in wild birds during recent years have been dominated by the H5N1 virus strain, the finding of HPAI H5N5 was likely this season and follows previous findings in Great Britain and recent detections of the strain in continental Europe.
Further update 5 November 2024
Highly pathogenic avian influenza (HPAI) H5N5 has been confirmed in commercial poultry at a premises near Hornsea, East Riding of Yorkshire, Yorkshire. All poultry on the infected premises will be humanely culled. A 3km protection zone and 10km surveillance zone has been put in place surrounding the premises.
Check if you’re in a bird flu disease zone on the map.
If you’re in a bird flu disease control zone you must follow the rules for that zone and check if you need a licence to move poultry, poultry by-products, eggs, material or mammals.
In line with World Organisation for Animal Health (WOAH) rules, this means Great Britain is no longer free from highly pathogenic avian influenza. Northern Ireland continues to have self-declared zonal freedom from highly pathogenic avian influenza.
Practicing good biosecurity at all times protects the health and welfare of your birds and for commercial keepers will help protect your business from HPAI and other diseases.
While it isn't clear how much of a player H5N5 will become, it has been increasingly reported across Europe, has crossed the Atlantic several times, and Ferrets inoculated with A(H5N5) viruses showed rapid, severe disease onset, with some evidence of direct contact transmission.
