title: Prospective study of avian influenza virus infections among rural Thai villagers.
abstract: BACKGROUND
  In 2008, 800 rural Thai adults living within Kamphaeng Phet Province were enrolled in a prospective cohort study of zoonotic influenza transmission. Serological analyses of enrollment sera suggested this cohort had experienced subclinical avian influenza virus (AIV) infections with H9N2 and H5N1 viruses.
  
  
  METHODS
  After enrollment, participants were contacted weekly for 24 mos for acute influenza-like illnesses (ILI). Cohort members confirmed to have influenza A infections were enrolled with their household contacts in a family transmission study involving paired sera and respiratory swab collections. Cohort members also provided sera at 12 and 24 months after enrollment. Serologic and real-time RT-PCR assays were performed against avian, swine, and human influenza viruses.
  
  
  RESULTS
  Over the 2 yrs of follow-up, 81 ILI investigations in the cohort were conducted; 31 (38%) were identified as influenza A infections by qRT-PCR. Eighty-three household contacts were enrolled; 12 (14%) reported ILIs, and 11 (92%) of those were identified as influenza infections. A number of subjects were found to have slightly elevated antibodies against avian-like A/Hong Kong/1073/1999(H9N2) virus: 21 subjects (2.7%) at 12-months and 40 subjects (5.1%) at 24-months. Among these, two largely asymptomatic acute infections with H9N2 virus were detected by >4-fold increases in annual serologic titers (final titers 1:80). While controlling for age and influenza vaccine receipt, moderate poultry exposure was significantly associated with elevated H9N2 titers (adjusted OR = 2.3; 95% CI, 1.04-5.2) at the 24-month encounter. One subject had an elevated titer (1:20) against H5N1 during follow-up.
  
  
  CONCLUSIONS
  From 2008-10, evidence for AIV infections was sparse among this rural population. Subclinical H9N2 AIV infections likely occurred, but serological results were confounded by antibody cross-reactions. There is a critical need for improved serological diagnostics to more accurately detect subclinical AIV infections in humans.
authors: College of Public Health and Health Professions and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America.
authors: Whitney S
authors: WS
authors: Krueger
authors: Benjawan
authors: B
authors: Khuntirat
authors: In-Kyu
authors: IK
authors: Yoon
authors: Patrick J
authors: PJ
authors: Blair
authors: Malinee
authors: M
authors: Chittagarnpitch
authors: Shannon D
authors: SD
authors: Putnam
authors: Krongkaew
authors: K
authors: Supawat
authors: Robert V
authors: RV
authors: Gibbons
authors: Darunee
authors: D
authors: Bhuddari
authors: Sirima
authors: S
authors: Pattamadilok
authors: Pathom
authors: P
authors: Sawanpanyalert
authors: Gary L
authors: GL
authors: Heil
authors: Gregory C
authors: GC
authors: Gray
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D058345:Asymptomatic Infections; D001717:Birds; D003429:Cross Reactions; D005260:Female; D006801:Humans; D015994:Incidence; D053124:Influenza A Virus, H5N1 Subtype / Q000302:isolation & purification*; D053127:Influenza A Virus, H9N2 Subtype / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000453:epidemiology / Q000635:transmission; D007251:Influenza, Human / Q000097:blood / Q000453:epidemiology* / Q000276:immunology / Q000635:transmission; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D016865:Reassortant Viruses / Q000302:isolation & purification*; D012424:Rural Population; D013785:Thailand / Q000453:epidemiology
chemical_list: D000914:Antibodies, Viral
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