Prospective Study of Avian Influenza Virus Infections among Rural Thai Villagers
Krueger W.S. Khuntirat B. Yoon I.-K. Blair P.J. Chittagarnpitch M. Putnam S.D. Supawat K. Gibbons R.V. Bhuddari D. Pattamadilok S.
Krueger W.S.
Khuntirat B.
Yoon I.-K.
Blair P.J.
Chittagarnpitch M.
Putnam S.D.
Supawat K.
Gibbons R.V.
Bhuddari D.
Pattamadilok S.
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Alternative Title
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 24mos 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.
Keywords
virus antibody, virus antibody, age, animal cell, antibody titer, article, avian influenza, avian influenza virus, cohort analysis, controlled study, cross reaction, family, follow up, household, human, influenza A, Influenza virus, Influenza virus A H5N1, Influenza virus A H9N2, major clinical study, nonhuman, poultry, prospective study, reverse transcription polymerase chain reaction, rural area, serology, swine influenza virus, Thailand, virus transmission, animal, asymptomatic infection, bird, blood, epidemiology, female, genetic reassortment, immunology, incidence, Influenza in Birds, Influenza, Human, isolation and purification, male, middle aged, rural population, transmission, Animals, Antibodies, Viral, Asymptomatic Infections, Birds, Cross Reactions, Female, Humans, Incidence, Influenza A Virus, H5N1 Subtype, Influenza A Virus, H9N2 Subtype, Influenza in Birds, Influenza, Human, Male, Middle Aged, Prospective Studies, Reassortant Viruses, Rural Population, Thailand
Source Title
PLoS ONE
Publisher
Public Library of Science
Series/Report No.
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Date
2013
DOI
10.1371/journal.pone.0072196
Type
Article