Avian flu confirmed in commercial turkey flock in California

[DhhD]

3. Origin of H5N8 from other Subtypes; H5N8 being HPAI-highly pathogenic avian influenza.

http://wwwnc.cdc.gov/eid/article/20/6/pdfs/14-0233.pdf

snip
A BLAST (www.ncbi.nlm.nih.
gov/genomes/FLU/FLU.html) search
and phylogenetic analysis showed
that these novel H5N8 subtype viruses
likely originated from reassortment between A/duck/Jiangsu/k1203/2010
(H5N8) virus and other subtypes of
avian influenza virus, all of which cocirculated
in birds in eastern China
during 2009–2012 (10). A phylogenetic
tree of partial HA gene sequences
for the 3 virus isolates from South
Korea and other H5 subtype viruses (n
= 72), showed that Gochang1, Buan2,
and Donglime3 belong to the proposed
H5 clade 2.3.4.6 (Figure) (10).


More at site source. On Page 2, of three pages, is a clade of the phylogeny of Subtypes.

As you can see the subtype genes can move between viruses in the same organism. There are several web links to more information in the study.


I believe that the current Flu Vaccine (not for Avian Flu) is based on immunization for Subtype genes for current human A and B types.