UK Confirms HPAI H5N5 In 2 Grey Seals

 

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While most of our HPAI concerns center around the H5N1 subtype, we continue to watch other strains (H5N6, H5N5, H5N9, etc.) with considerable interest since history has shown how quickly an obscure subtype can take center stage (see EID Journal: Comparison of 2016–17 and Previous Epizootics of HPAI H5 In Europe).

In China, H5N6 continues to spill over into humans, killing roughly 50% of those hospitalized.  In Europe, and in Canada, we are watching a milder H5N5 virus circulate in wild birds, and occasionally spill over into mammals. 

Both have some degree of pandemic potential, but neither has spread as efficiently as the current HPAI H5N1 threat.  

Today, in a brief notice (see above), the UK has announced the detection of HPAI H5N5 in two grey seals, detected in Norfolk.   Last November, they reported an outbreak in poultry of H5N5 in Yorkshire along with > 2 dozen dead birds infected with H5N5 from around the kingdom (see map below).

While this latest report hasn't appeared on the WOAH WAHIS list, that organization has already published 11 reports on H5N5 in birds and mammals since the first of the year from 6 different countries (Norway, Canada, Iceland, Greenland, Germany & the UK). 

A few recent blogs on this subtype include:

Virus Evolution: Recurring Incursions & Dissemination of Novel Eurasian-origin H5Nx Avian Influenza Viruses in Atlantic Canada

More Reports On HPAI H5N5 In Iceland

Icelandic Food and Veterinary Authority (MAST) : H5N5 Infection In Domestic Cat

We've seen reports of H5N5 in European birds going back to 2016, but it was first detected in dead raccoons on Prince Edward Island about 21 months ago (see CIDRAP Report). Since last May, we've seen increasing reports of its western expansion (see 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:

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.

While H5N5 is likely to remain a minor player, it is not impossible that we could the threat shift to H5N1 to H5N5, or H5N6, or to some other n-type, in the months or years ahead.  After all, 5 years ago H5N1 was in serious decline, while HPAI H5N8 reigned supreme. 

The H5Nx virus has an large - and growing - array of diverse hosts to inhabit, and no lack of genetic diversity on which to draw. All reasons why we could always see additional shifts in the fluscape in the future.