title: Absence of neutralizing antibodies against influenza A/H5N1 virus among children in Kamphaeng Phet, Thailand.
abstract: BACKGROUND
  Influenza A/H5N1 actively circulated in Kamphaeng Phet (KPP), Thailand from 2004 to 2006. A prospective longitudinal cohort study of influenza virus infection in 800 adults conducted during 2008-2010 in KPP suggested that subclinical or mild H5N1 infections had occurred among this adult cohort. However, this study was conducted after the peak of H5N1 activity in KPP. Coincidentally, banked serum samples were available from a prospective longitudinal cohort study of primary school children who had undergone active surveillance for febrile illnesses from 2004 to 2007 and lived in the same district of KPP as the adult cohort.
  
  
  OBJECTIVE
  We sought to investigate whether subclinical or mild H5N1 infections had occurred among KPP residents during the peak of H5N1 activity from 2004 to 2006.
  
  
  METHODS
  H5N1 microneutralization (MN) assay was performed on banked serum samples from a prospective longitudinal cohort study of primary school children who had undergone active surveillance for febrile illnesses in KPP. Annual blood samples collected from 2004 to 2006 from 251 children were selected based on the criteria that they lived in villages with documented H5N1 infection.
  
  
  RESULTS
  No H5N1 neutralizing antibodies were detected in 753 annual blood samples from 251 children.
  
  
  CONCLUSIONS
  During 2004-2006, very few subclinical or mild H5N1 infections occurred in KPP. Elevated H5N1 MN titers found in the adult cohort in 2008 were likely due to cross-reactivity from other influenza virus subtypes highlighting the complexities in interpreting influenza serological data.
authors.affiliation: Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand. Electronic address: BenjawanK@afrims.org.
authors.forename: Benjawan
authors.initials: B
authors.lastname: Khuntirat
authors.affiliation: Naval Medical Center Portsmouth, Portsmouth, VA, USA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Love
authors.affiliation: Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.
authors.forename: Darunee
authors.initials: D
authors.lastname: Buddhari
authors.affiliation: College of Public Health and Health Professions and Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.
authors.forename: Gary L
authors.initials: GL
authors.lastname: Heil
authors.affiliation: Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.
authors.forename: Robert V
authors.initials: RV
authors.lastname: Gibbons
authors.affiliation: Institute for Immunology and Informatics, University of Rhode Island, Providence, Rhode Island, USA.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Rothman
authors.affiliation: Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA.
authors.forename: Anon
authors.initials: A
authors.lastname: Srikiatkhachorn
authors.affiliation: College of Public Health and Health Professions and Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Gray
authors.affiliation: Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.
authors.forename: In-Kyu
authors.initials: IK
authors.lastname: Yoon
mesh_terms: D000293:Adolescent; D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood*; D000914:Antibodies, Viral / Q000097:blood*; D058345:Asymptomatic Infections / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003429:Cross Reactions; D005260:Female; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000276:immunology* / Q000821:virology; D008137:Longitudinal Studies; D008297:Male; D009500:Neutralization Tests; D011446:Prospective Studies; D013785:Thailand / Q000453:epidemiology; D013997:Time Factors
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral
keywords: Avian influenza; H5N1; Microneutralization; Serology; Subclinical infection