The geographical spread of avian influenza A (H5N1): Panzootic transmission (December 2003-May 2006), pandemic potential, and implications

Abstract

The World Health Organization (WHO) believes that the advent of highly pathogenic avian influenza A (H5N1) has moved the world closer to a further global pandemic of human influenza than at any time since the Hong Kong (H3N2) pandemic of 1968-1969. The immediacy of the perceived threat is underscored by the current classification of the world at Phase 3 of WHO's operative six-phase system of pandemic alert, with H5N1 having met all the prerequisites for the onset of a human pandemic but one: the efficient and sustained person-to-person transmission of the virus. With preparations for an anticipated pandemic now recognized as a global health priority, the purpose of this article is to provide a foundation for geographical research on avian influenza A (H5N1). The article introduces geographers to the complex nature and ecology of H5N1, the principal data sources available to analyze the global occurrence of the virus in birds and humans, and evidence regarding its geographical origins and international dispersal during the first thirty months of the ongoing panzootic in wild birds and poultry, from December 2003 through May 2006. Key epidemiological facets of the disease in humans are examined. We conclude with a review of the incurred and projected economic costs of H5N1, global plans for pandemic aversion and mitigation, and prospects for the future geographical expansion of the virus. Areas in which geographers can make an effective contribution to knowledge about the virus and the disease are considered.