H5N1 in Asia

Abstract

The highly pathogenic H5N1 influenza virus that emerged in Southeastern Asia a decade ago has evolved into multiple genetic clades, spread from Asia to Europe and Africa, greatly compromised the poultry industry and endangered human health, and now poses a serious pandemic threat. The unique ecology of the long-established influenza epicenter of Southeastern Asia continues to play a role in driving the genetic diversity and possibly the persistence of H5N1 virus. Long-term surveillance in this region has provided insight into the emergence of H5N1 in Asia, establishment of the virus in this region, and potential routes of spread to other regions. Although highly pathogenic H5N1 virus can be lethal to wild waterfowl, this natural reservoir of all subtypes of influenza A virus is more resistant to the infection and demonstrates the ability to select antigenic variants with attenuated virulence in these species. Other unique characteristics of the H5N1 virus include an expanded host range to many Carnivora species and increased pathogenicity in mammals. Because multiple factors contribute to the spread and perseverance of H5N1 virus, integration of multifaceted strategies and global collaboration are necessary for effective control. © 2008 S. Karger AG.