We conducted phylogenetic and epidemiologic analyses to determine sources of outbreaks of highly pathogenic avian influenza virus (HPAIV), subtype H5N1, in poultry holdings in 2007 in Germany, and a suspected incursion of HPAIV into the food chain through contaminated deep-frozen duck carcasses. In summer 2007, HPAIV (H5N1) outbreaks in 3 poultry holdings in Germany were temporally, spatially, and phylogenetically linked to outbreaks in wild aquatic birds. Detection of HPAIV (H5N1) in frozen duck carcass samples of retained slaughter batches of 1 farm indicated that silent infection had occurred for some time before the incidental detection. Phylogenetic analysis established a direct epidemiologic link between HPAIV isolated from duck meat and strains isolated from 3 further outbreaks in December 2007 in backyard chickens that had access to uncooked offal from commercial deep-frozen duck carcasses. Measures that will prevent such undetected introduction of HPAIV (H5N1) into the food chain are urgently required.
Abattoirs* Animals Antibodies, Viral/blood Disease Outbreaks* Ducks/virology* Freezing Germany/epidemiology Immunoenzyme Techniques/methods Influenza A Virus, H5N1 Subtype*/genetics Influenza A Virus, H5N1 Subtype*/immunology Influenza A Virus, H5N1 Subtype*/isolation & purification Influenza A Virus, H5N1 Subtype*/pathogenicity Influenza in Birds/epidemiology* Influenza in Birds/virology Meat/virology* Phylogeny Poultry/virology* Poultry Diseases/epidemiology Poultry Diseases/virology