One of the things we've been waiting to see come out of Europe's H5N8 invasion has been the creation of new subtypes via the reassortment of H5N8 and other LPAI viruses that commonly circulate in wild birds.
When H5N8 arrived in North America in the fall of 2014 it quickly produced two offspring; a North American version of HPAI H5N1, and a highly pathogenic H5N2 virus (see EID Journal: Rapid Emergence Of Novel HPAI H5 Subtypes).
Until today we've only seen reports of H5N8 in Europe's current outbreak, but the OIE has posted the following notification of a single duck found to have a reassorted H5N5 virus. While genetic details are pending, this is likely to have emerged from a union between H5N8 and another local LPAI virus.
The North American HPAI H5N1 virus ended up being a very minor player in our epizootic of two years ago, while in some places HPAI H5N2 turned out to be a bigger problem than H5N8.
Meaning you never know how these emerging reassortants will sort themselves out.
This isn't our first encounter with HPAI H5N8, as we saw it in 2008 (albeit born of a different H5 clade), when two mallard ducks in Eastern China tested positive for a new subtype (see Novel H5N5 Avian Influenza Detected In China).
It never really took hold, but it was one of the first 2nd generation HPAI H5 viruses we saw spawn from H5N1.
The account of its discovery appeared in the 2011 EID Journal Dispatch called Novel Reassortant Highly Pathogenic Avian Influenza (H5N5) Viruses in Domestic Ducks, China, where they identified the likely parental viruses (H5N1 and H6N5) both circulating in local domestic ducks.
The future for HPAI H5N5 in Europe is still pretty cloudy, but unless we start seeing it in abundance, this is more likely to be an interesting footnote to the H5N8 story, not a headline.