Carrel et al 2010 PLoS ONE Fig5
Geographic distribution of H5N1 highly pathogenic avian
influenza viruses (HPAIVs) used in this study. Darkened
provinces indicate locations of virus isolation.

“We found several patterns that suggest one general model of evolution in this viral system: 1) within regions, viral mixing in poultry moves toward heterogeneity and the emergence of local types; 2) differentiation was centered around regional viral hubs located at centers of human and bird population density; and 3) evolution occurs because of relative isolation of the hubs, most likely fed by the abundant supply of domesticated poultry (and people) at the hubs. The analysis thus suggests that at the scale of neighboring city hubs and the intervening hinterland, evolution of H5N1 follows the pattern described by classical theory of genetic differentiation due to isolation by distance.” 1

Carrel et al 2010 PLoS ONE Fig1
Genetic versus geographic distance of HK821-like HPAIVs in Vietnam.

This is in Vietnam, and the basic finding was that H5N1 viruses isolated in Vietnam show signs of local evolution, in that the viruses cluster into local sub-strains in different areas of the country.  I’m not all that knowledgeable about H5N1 spread, but I had thought that infection of wild, especially migratory, birds would be an important factor in spreading H5N1 between chickens.  If I’m interpreting this paper right, it looks as if H5N1 is mostly circulating within local regions, within the chicken population, and distant spread isn’t a major factor. That has obvious implications for control of the virus.

  1. Carrel, M., Emch, M., Jobe, R., Moody, A., & Wan, X. (2010). Spatiotemporal Structure of Molecular Evolution of H5N1 Highly Pathogenic Avian Influenza Viruses in Vietnam PLoS ONE, 5 (1) DOI: 10.1371/journal.pone.0008631[]