Phylogeographic analysis of avian influenza viruses isolated from Charadriiformes in Belgium confirms intercontinental reassortment in gulls.

Nine influenza viruses isolated from gulls and shorebirds in Belgium (2008-2010), including H3N8, H5N2, H6N1, H11N9, H13N6, H13N8, and H16N3 subtypes, were targeted using random amplification and next-generation sequencing. The gene segments of these viruses segregated into three phylogeographic lineage types: (1) segments circulating in waterfowl in Eurasia with sporadic introduction in other species and in the Americas ("Eurasian avian"), (2) segments circulating in American waterfowl with sporadic introduction to other species and regions ("American avian"), and (3) segments circulating exclusively in gulls and shorebirds and having increased connectivity between the two hemispheres ("Charadriiformes specific"). Notably, an H6N1 and an H5N2 isolated from L. argentatus had mainly Eurasian avian genes but shared a matrix segment of American avian origin (first documentation in European gulls of transhemispheric reassortment). These data support the growing evidence of an important role of Charadriiformes birds in the dynamic nature of avian influenza ecology.