Global and local persistence of influenza A(H5N1) virus

Abstract

An understanding of the global migration dynamics of highly pathogenic avian influenza A(H5N1) virus is helpful for surveillance and disease prevention. To characterize the migration network of this virus, we used genetic analysis, which supported a global persistence model in which each of 9 regions acts to some extent as a source. Siberia is the major hub for the dispersal of the virus. Southeast Asia and Africa are major sources of genetically and antigenically novel strains. We found evidence of local persistence of the virus in Southeast Asia and Africa, which is rare for human influenza A viruses. The differences in migration dynamics between avian and human influenza viruses might help with the design of region-specific surveillance efforts and the selection of vaccine candidates.

Keywords: H5N1; avian influenza; influenza; migration network; persistence; source; viruses.

Figure 1

Global migration patterns of highly pathogenic avian influenza A(H5N1) viruses estimated from sequence data sampled during 1996–2012. Arrows represent direction of movement, and arrow width is proportional to the migration rate. Migration rates <0.07 migration events per lineage per year are not shown. The area of each circle is proportional to the region’s eigenvector centrality; larger circles indicate crucial nodes in the migration network.

Figure 2

Estimated genealogy of 3,365 highly pathogenic avian influenza A(H5N1) viruses sampled during 1996–2012. The maximum a posteriori tree was estimated by using Migrate version 3.3.0 (21,22). Each tip represents a virus sequence. Colors indicate the sampling region, either actual (tips) or estimated (branches).

Figure 3

Temporal changes in geographic regions along the trunk of the highly pathogenic avian influenza A(H5N1) virus genealogical tree.

Figure 4

Bayesian skyride median of relative genetic diversity of highly pathogenic avian influenza (H5N1) virus in each region, 2006–2011. Shading represents winter (October–March) in the Northern Hemisphere.