The multiple origins of the H5N8 avian influenza sub-type

A significant outbreak of H5N8 avian influenza began in early 2014 in Korea. H5N8 is a highly pathogenic avian influenza that is often fatal to chickens and other domestic poultry but which can be asymptomatic in ducks. The virus was also found in migratory birds in Europe and more recently in North America. This is the first time that an H5N8 outbreak has spread so widely and persisted for so long. Previous outbreaks have usually been short and geographically localised. In this study I present a phylogenetic analysis of all of the H5 hemagglutinin and N8 neuraminidase sequences to show that each of the H5N8 outbreaks has resulted from a different re-assortment event and that there have been at least 7 distinct origins of the viral sub-type since it was first characterised in a Turkey in Ireland in 1983.