Submitted to: Emerging Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2005
Publication Date: 10/30/2005
Citation: Donis, R., Lee, C.W., Suarez, D.L., Spackman, E., Swayne, D.E. 2005. Evolution of H5N1 avian influenza viruses in asia: antigenicity, antiviral drug sensitivity and vaccine development. Emerging Infectious Diseases. 10:1515-1521. Interpretive Summary: The H5N1 high pathogenicity avian influenza (HPAI) virus has caused the largest outbreak in poultry, involving 9 Asian countries. The H5N1 HPAI has also caused human infections and death. This multiple institution project compared the relationships between viruses from multiple countries over several years. The human isolates were all closely related and were resistant to one antiviral drug but susceptible to another. A vaccine virus has been developed through reverse genetics and has potential for vaccination of human population at risk to infection by H5N1 HPAI viruses.
Technical Abstract: An unparalleled outbreak of highly pathogenic avian influenza A (H5N1) has recently spread to poultry in 9 Asian countries. H5N1 infections have caused at least 52 human deaths in Vietnam, Thailand and Cambodia between January 2004 and April 2005. Genomic analyses of H5N1 isolates from birds and humans revealed two distinct clades, which showed a non-overlapping geographic distribution. All the viral genes were of avian influenza origin, indicating absence of reassortment with human influenza viruses. All human H5N1 isolates tested belonged to a single clade and were resistant to the adamantane drugs but sensitive to neuraminidase inhibitors. Most H5N1 isolates from humans were antigenically homogeneous and distinct from viruses circulating before the end of 2003. Some 2005 isolates showed evidence of antigenic drift. An updated non-pathogenic H5N1 reference viruses, lacking the polybasic cleavage site in the HA, were produced by reverse genetics in anticipation of the possible need to vaccinate the human population at risk.