Novel reassortant highly pathogenic avian influenza (H5N5) viruses in domestic ducks, China

Abstract

In China, domestic ducks and wild birds often share the same water, in which influenza viruses replicate preferentially. Isolation of 2 novel reassortant highly pathogenic avian influenza (H5N5) viruses from apparently healthy domestic ducks highlights the role of these ducks as reassortment vessels. Such new subtypes of influenza viruses may pose a pandemic threat.

Figure 1

Phylogenetic trees of hemagglutinin (A) and neuraminidase (B) genes of novel avian influenza (H5N5) viruses isolated from domestic ducks in the People’s Republic of China, December 2008–January 2009, with reference sequences. Green, A/duck/eastern China/008/2008 (H5N5) and A/duck/eastern China/031/2009 (H5N5); purple, A/duck/eastern China/108/2008 (H5N1) and A/duck/eastern China/909/2009 (H5N1); blue, A/duck/Yangzhou/013/2008 (H6N5); boldface, other H5N5 influenza viruses available from GenBank. Inset boxes in panel B indicate correspondence between thumbnail and panorama of related perspectives. Trees were generated by applying the neighbor-joining method in MEGA 4.0 (www.megasoftware.net) on the basis of full-length coding sequences. Numbers above or below the branch nodes indicate bootstrap values. Scale bars indicate branch length based on number of nucleotide substitutions per site.

Figure 2

Putative genomic compositions of the novel avian influenza (H5N5) viruses isolated from domestic ducks in the People’s Republic of China, December 2008–January 2009, with their possible donors. The 8 gene segments (from top to bottom) in each virus are polymerase basic protein 2, polymerase basic protein 1, polymerase acidic protein, hemagglutinin (HA), nucleocapsid protein, neuraminidase, matrix protein, and nonstructural protein. Each color indicates a separate virus background. Dashed lines indicate high sequence identity and suggest a second possibility that the 2 influenza (H5N5) viruses could be donors of some gene segments for each other. 108, A/duck/eastern China/108/2008 (H5N1); 909, A/duck/eastern China/909/2009 (H5N1); 008, A/duck/eastern China/008/2008 (H5N5); 031, A/duck/eastern China/031/2009 (H5N5); 013, A/duck/Yangzhou/013/2008 (H6N5). H?N5 denotes possible parental viruses of unidentified HA subtype but N5 subtype. The simplified schematic illustration is based on nucleotide-distance comparison and phylogenetic analysis.