title: Intense circulation of A/H5N1 and other avian influenza viruses in Cambodian live-bird markets with serological evidence of sub-clinical human infections.
abstract: Surveillance for avian influenza viruses (AIVs) in poultry and environmental samples was conducted in four live-bird markets in Cambodia from January through November 2013. Through real-time RT-PCR testing, AIVs were detected in 45% of 1048 samples collected throughout the year. Detection rates ranged from 32% and 18% in duck and chicken swabs, respectively, to 75% in carcass wash water samples. Influenza A/H5N1 virus was detected in 79% of samples positive for influenza A virus and 35% of all samples collected. Sequence analysis of full-length haemagglutinin (HA) and neuraminidase (NA) genes from A/H5N1 viruses, and full-genome analysis of six representative isolates, revealed that the clade 1.1.2 reassortant virus associated with Cambodian human cases during 2013 was the only A/H5N1 virus detected during the year. However, multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of HA and NA genes revealed co-circulation of at least nine low pathogenic AIVs from HA1, HA2, HA3, HA4, HA6, HA7, HA9, HA10 and HA11 subtypes. Four repeated serological surveys were conducted throughout the year in a cohort of 125 poultry workers. Serological testing found an overall prevalence of 4.5% and 1.8% for antibodies to A/H5N1 and A/H9N2, respectively. Seroconversion rates of 3.7 and 0.9 cases per 1000 person-months participation were detected for A/H5N1 and A/H9N2, respectively. Peak AIV circulation was associated with the Lunar New Year festival. Knowledge of periods of increased circulation of avian influenza in markets should inform intervention measures such as market cleaning and closures to reduce risk of human infections and emergence of novel AIVs.
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.
authors.forename: Srey Viseth
authors.initials: SV
authors.lastname: Horm
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Tarantola
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.
authors.forename: Sareth
authors.initials: S
authors.lastname: Rith
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.
authors.forename: Sowath
authors.initials: S
authors.lastname: Ly
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.
authors.forename: Juliette
authors.initials: J
authors.lastname: Gambaretti
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.
authors.forename: Veasna
authors.initials: V
authors.lastname: Duong
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.
authors.forename: Phalla
authors.initials: P
authors.lastname: Y
authors.affiliation: National Veterinary Research Institute, Ministry of Agriculture, Forestry and Fisheries, Phnom Penh 12000, Cambodia.
authors.forename: San
authors.initials: S
authors.lastname: Sorn
authors.affiliation: National Veterinary Research Institute, Ministry of Agriculture, Forestry and Fisheries, Phnom Penh 12000, Cambodia.
authors.forename: Davun
authors.initials: D
authors.lastname: Holl
authors.affiliation: Food and Agriculture Organization, Phnom Penh 12000, Cambodia.
authors.forename: Lotfi
authors.initials: L
authors.lastname: Allal
authors.affiliation: Food and Agriculture Organization, Bangkok 10200, Thailand.
authors.forename: Wantanee
authors.initials: W
authors.lastname: Kalpravidh
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.
authors.forename: Philippe
authors.initials: P
authors.lastname: Dussart
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.
authors.forename: Paul F
authors.initials: PF
authors.lastname: Horwood
authors.affiliation: Institute Pasteur in Cambodia, Institute Pasteur International Network, Phnom Penh 12000, Cambodia.|GlaxoSmithKline Pte Ltd, Singapore 189720, Singapore.
authors.forename: Philippe
authors.initials: P
authors.lastname: Buchy
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D058345:Asymptomatic Infections / Q000453:epidemiology*; D002160:Cambodia / Q000453:epidemiology; D002645:Chickens / Q000821:virology; D004372:Ducks / Q000821:virology; D000067565:Farmers; D005814:Genes, Viral; D016679:Genome, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D053127:Influenza A Virus, H9N2 Subtype / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D005585:Influenza in Birds / Q000097:blood / Q000453:epidemiology* / Q000635:transmission / Q000821:virology*; D007251:Influenza, Human / Q000097:blood / Q000453:epidemiology* / Q000821:virology; D009439:Neuraminidase / Q000235:genetics; D010802:Phylogeny; D011201:Poultry Diseases / Q000097:blood / Q000821:virology*; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D016036:Seroepidemiologic Studies
chemical_list: D000914:Antibodies, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D009439:Neuraminidase