Highly pathogenic avian influenza (HPAI) type A of the subtype H5N1 has recently spread widely and rapidly across Eurasia, and even to Africa, with deaths of both wild and domestic birds recorded. There are fears that it may soon spread to the Americas. Media accounts, communications from international bodies and national governments, and even some of the professional research literature attributes the spread, in part, to movements of HP strains by migratory birds. The origin of highly pathogenic strains is attributed to mutations, or to reassortment of virus genes from different host species. In this paper we review these hypotheses in light of knowledge about the ecology and evolution of avian influenza, looked at from the viewpoint of its natural reservoir - waterbirds. Our purpose here is to alert waterbird biologists that they have much to contribute to the science of this globally-important issue. New technologies have revealed that the genome of avian influenza contains much variation beyond that recognizable by classical antibody techniques, and have established avian influenza as a rapidly evolving and diversifying lineage. The extensive genetic variability in the viral genome and extensive reassortment within host species suggests that high pathogenicity could repeatedly and independently evolve from low pathogenic ancestors under appropriate selection pressures, such as those in poultry production systems. This makes infection of wild birds by HPAI lineages evolved in poultry a more likely occurrence than the reverse. The available evidence largely fits this model. We make recommendations that will help reduce the incursion of domestically-evolved avian influenza strains into wild populations of birds.
|Publication status||Published - 2006|
- a viruses
- pandemic influenza