Movements of birds and avian influenza from Asia into Alaska

Abstract

Asian-origin avian influenza (AI) viruses are spread in part by migratory birds. In Alaska, diverse avian hosts from Asia and the Americas overlap in a region of intercontinental avifaunal mixing. This region is hypothesized to be a zone of Asia-to-America virus transfer because birds there can mingle in waters contaminated by wild-bird-origin AI viruses. Our 7 years of AI virus surveillance among waterfowl and shorebirds in this region (1998-2004; 8,254 samples) showed remarkably low infection rates (0.06%). Our findings suggest an Arctic effect on viral ecology, caused perhaps by low ecosystem productivity and low host densities relative to available water. Combined with a synthesis of avian diversity and abundance, intercontinental host movements, and genetic analyses, our results suggest that the risk and probably the frequency of intercontinental virus transfer in this region are relatively low.

Figure

Composite geographic information system map illustrating the overlap of New World and Old World migration systems among 64 species of waterfowl (family Anatidae) and shorebirds (families Charadriidae and Scolopacidae) in northern and western Alaska (darkness of shade indicates species richness). This overlap between Asiatic and American birds in these families occurs in a zone whose extent is equivalent to a geographic band running from Lake Superior to North Dakota then to Texas and California in the lower 48 US states (left inset).