Avian influenza in the Western Hemisphere including the Pacific Islands and Australia

Between 1997 and 2001, there was one report of highly pathogenic avian influenza (HPAI) in the Western Hemisphere and Pacific Basin. In 1997, in New South Wales, Australia, an outbreak caused by avian influenza (AI) virus subtype H7N4 involved both chickens and emus. All other reports of infections in poultry and isolations from wild bird species in the region pertained to low pathogenicity, (LP) AI virus. Animal Health Officials in Canada reported isolations of subtypes H1, H6, H7, and H10 from domestic poultry and subtypes H3 and H13 from imported and wild bird species. In Mexico, the H5N2 LPAI virus, the precursor of the HPAI outbreak in 1994-95, was isolated from poultry in each year from 1997 to 2001. Since 1997, Mexico has used approximately 708 million doses of a killed H5N2 vaccine and an additional 459 million doses of a recombinant fowlpox-H5 vaccine in their H5N2 control program. In Central America, avian influenza was diagnosed for the first time when H5N2 LPAI virus was isolated from chickens in Guatemala and El Salvador in 2000 and 2001, respectively. The H5N2 virus was genetically similar to the H5N2 virus found in Mexico. Surveillance activities in the United States resulted in the detection of AI virus or specific antibodies in domestic poultry from 24 states. Eleven of the fifteen hemagglutinin (H1, H2, H3, H4, H5, H6, H7, H9, H10, H11, and H13) and eight of the nine neuraminidase (N1, N2, N3, N4, N6, N7, N8, and N9) subtypes were identified. Two outbreaks of LPAI virus were reported in commercial table-egg producing chickens; one caused by H7N2 virus in Pennsylvania in 1996-98 and the other caused by H6N2 virus in California in 2000-01. In addition, isolations of H5 and H7 LPAI virus were recovered from the live-bird markets (LBMs) in the northeast United States.