Avian influenza in North and South America, 2002-2005.

Between 2002 and 2005, three outbreaks of highly pathogenic avian influenza (HPAI) occurred in the Americas: one outbreak in Chile (H7N3) in 2002, one outbreak in the United States (H5N2) in 2004, and one outbreak in Canada (H7N3) in 2004. The outbreak in Chile was limited to a large broiler breeder operation and a nearby turkey flock and represented the first outbreak of HPAI in that country. The outbreak of HPAI in the United States occurred in Texas and was limited to one premise where chickens were raised for sale in nearby live-bird markets. The outbreak in Canada was the largest of the three HPAI outbreaks, involving 42 premises and approximately 17 million birds in the Fraser Valley, British Columbia. In each of the HPAI outbreaks, the disease was successfully eradicated by depopulation of infected farms. All other reports of infections in poultry and isolations from wild bird species pertained to low pathogenicity avian influenza (LPAI) viruses. Animal Health Officials in Canada reported subtypes H3, H5, and H6 in domestic poultry, and H3, H5, H11, and H13 from imported and/or wild bird species. An LPAI H5N2 virus continues to circulate in Mexico and the Central American countries of Guatemala and El Salvador. Each country reported isolations of H5N2 virus from poultry and the large-scale use of inactivated and recombinant H5 vaccines in their AI control programs. In Colombia, AI was reported for the first time when antibodies to H9N2 were detected in chickens by routine surveillance. Intensive surveillance activities in the United States detected AI virus or specific antibodies to 13 of the 16 hemagglutinin (H1-H13) and all nine neuraminidase subtypes in live-bird markets, small holder farms, and in commercial poultry from 29 states. The largest outbreak of LPAI in the United States occurred in 2002, when 197 farms were depopulated (4.7 million birds) to control an outbreak in Virginia and surrounding states. The outbreak was caused by an LPAI H7N2 virus closely related to an H7N2 virus that has been circulating in the live-bird marketing system in the northeastern United States since 1994.