title: Changes in adaptation of H5N2 highly pathogenic avian influenza H5 clade 2.3.4.4 viruses in chickens and mallards.
abstract: H5N2 highly pathogenic avian influenza (HPAI) viruses caused a severe poultry outbreak in the United States (U.S.) during 2015. In order to examine changes in adaptation of this viral lineage, the infectivity, pathogenicity and transmission of poultry H5N2 viruses were investigated in chickens and mallards in comparison to the wild duck 2014 U.S. index H5N2 virus. The four poultry isolates examined had a lower mean bird infectious dose than the index virus but still transmitted poorly to direct contacts. In mallards, two of the H5N2 poultry isolates had similar high infectivity and transmissibility as the index H5N2 virus, the H5N8 U.S. index virus, and a 2005 H5N1 clade 2.2 virus. Mortality occurred with the H5N1 virus and, interestingly, with one of two poultry H5N2 isolates. Increased virus adaptation to chickens was observed with the poultry H5N2 viruses; however these viruses retained high adaptation to mallards but pathogenicity was differently affected.
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA. Electronic address: eric.dejesus@ars.usda.gov.
authors.forename: Eric
authors.initials: E
authors.lastname: DeJesus
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA. Electronic address: mar.costa-hurtado@umontreal.ca.
authors.forename: Mar
authors.initials: M
authors.lastname: Costa-Hurtado
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA. Electronic address: diane.smith@ars.usda.gov.
authors.forename: Diane
authors.initials: D
authors.lastname: Smith
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA. Electronic address: donghun.lee@ars.usda.gov.
authors.forename: Dong-Hun
authors.initials: DH
authors.lastname: Lee
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA. Electronic address: erica.spackman@ars.usda.gov.
authors.forename: Erica
authors.initials: E
authors.lastname: Spackman
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA. Electronic address: darrell.kapczynski@ars.usda.gov.
authors.forename: Darrell R
authors.initials: DR
authors.lastname: Kapczynski
authors.affiliation: National Veterinary Services Laboratories, Veterinary Services, U.S. Department of Agriculture, Ames, IA, USA. Electronic address: mia.kim.torchetti@aphis.usda.gov.
authors.forename: Mia Kim
authors.initials: MK
authors.lastname: Torchetti
authors.affiliation: National Veterinary Services Laboratories, Veterinary Services, U.S. Department of Agriculture, Ames, IA, USA. Electronic address: mary.l.killian@aphis.usda.gov.
authors.forename: Mary L
authors.initials: ML
authors.lastname: Killian
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA. Electronic address: david.suarez@ars.usda.gov.
authors.forename: David L
authors.initials: DL
authors.lastname: Suarez
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA. Electronic address: david.swayne@ars.usda.gov.
authors.forename: David E
authors.initials: DE
authors.lastname: Swayne
authors.affiliation: Exotic and Emerging Avian Viral Diseases Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA. Electronic address: mary.pantin-jackwood@ars.usda.gov.
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Pantin-Jackwood
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D002645:Chickens; D004372:Ducks; D014644:Genetic Variation; D053125:Influenza A Virus, H5N2 Subtype / Q000145:classification* / Q000502:physiology*; D005585:Influenza in Birds / Q000401:mortality / Q000635:transmission / Q000821:virology*; D012367:RNA, Viral; D017422:Sequence Analysis, DNA; D019562:Viral Load; D017201:Virus Shedding
chemical_list: D012367:RNA, Viral
keywords: Adaptation; Chickens; H5N1; H5N2; H5N8; Highly pathogenic avian influenza virus; Infectivity; Mallards; Pathogenicity; Transmission