Post Reply - A new pandemic

Five weeks ago the UK made a brief announcement on the detection of  HPAI H5N5 In 2 Grey Seals in Norfolk.  This was the first detection of HPAI H5 in a non-avian species in the UK in nearly 2 years, and the first such detection involving the H5N5 subtype. 

HPAI H5N5 is a reassortant offshoot of the clade 2.3.4.4b H5N1 virus, which has turned up sporadically in European birds, cats in Iceland, birds in the the UK - and since 2023 in Canada - infecting both birds and mammals.

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.

Over the weekend the UK's APHA announced the detection of an additional 13 grey seals with H5N5, and the disclosure that the mammalian E627K mutation was detected as well. 

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While H5N5 remains a minor player, it is not impossible that we could a shift from H5N1 to H5N5, or H5N6 (or to some other n-type), in the months or years ahead. After all, little more than  5 years ago H5N1 was in serious decline, while HPAI H5N8 was dominant.  

The H5Nx virus has an large - and growing - array of diverse avian and mammalian hosts to inhabit, and no lack of genetic diversity on which to draw. 

While past performance is no guarantee of future results, its current trajectory is nevertheless concerning.