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Transmission Dynamics of Highly Pathogenic Avian Influenza Virus A(H5Nx) Clade, North America, 2014–2015

David Swayne, Dong-Hun Lee, Mia Torchetti, Joseph Hicks, Mary Killian, Justin Bahl, Mary Pantin-Jackwood
Emerging infectious diseases 2018 v.24 no.10 pp. 1840-1848
Influenza A virus, biosecurity, chickens, disease transmission, farms, genomics, nucleotide sequences, outbreak investigation, poultry industry, turkeys, viruses, wild birds, Eurasia, United States
Eurasia highly pathogenic avian influenza virus (HPAIV) H5 clade emerged in North America at the end of 2014 and caused outbreaks affecting >50 million poultry in the United States before eradication in June 2015. We investigated the underlying ecologic and epidemiologic processes associated with this viral spread by performing a comparative genomic study using 268 full-length genome sequences and data from outbreak investigations. Reassortant HPAIV H5N2 circulated in wild birds along the Pacific flyway before several spillover events transmitting the virus to poultry farms. Our analysis suggests that >3 separate introductions of HPAIV H5N2 into Midwest states occurred during March–June 2015; transmission to Midwest poultry farms from Pacific wild birds occurred ≈1.7–2.4 months before detection. Once established in poultry, the virus rapidly spread between turkey and chicken farms in neighboring states. Enhanced biosecurity is required to prevent the introduction and dissemination of HPAIV across the poultry industry.