Links to Exploration step
Le document en format XML
<record><TEI><teiHeader><fileDesc><titleStmt><title xml:lang="en">A Serological Survey of Antibodies to H5, H7 and H9 Avian Influenza Viruses amongst the Duck-Related Workers in Beijing, China</title>
<author><name sortKey="Yang, Peng" sort="Yang, Peng" uniqKey="Yang P" first="Peng" last="Yang">Peng Yang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Ma, Chunna" sort="Ma, Chunna" uniqKey="Ma C" first="Chunna" last="Ma">Chunna Ma</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Shi, Weixian" sort="Shi, Weixian" uniqKey="Shi W" first="Weixian" last="Shi">Weixian Shi</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Cui, Shujuan" sort="Cui, Shujuan" uniqKey="Cui S" first="Shujuan" last="Cui">Shujuan Cui</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Lu, Guilan" sort="Lu, Guilan" uniqKey="Lu G" first="Guilan" last="Lu">Guilan Lu</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Peng, Xiaomin" sort="Peng, Xiaomin" uniqKey="Peng X" first="Xiaomin" last="Peng">Xiaomin Peng</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Zhang, Daitao" sort="Zhang, Daitao" uniqKey="Zhang D" first="Daitao" last="Zhang">Daitao Zhang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Liu, Yimeng" sort="Liu, Yimeng" uniqKey="Liu Y" first="Yimeng" last="Liu">Yimeng Liu</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Liang, Huijie" sort="Liang, Huijie" uniqKey="Liang H" first="Huijie" last="Liang">Huijie Liang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Zhang, Yi" sort="Zhang, Yi" uniqKey="Zhang Y" first="Yi" last="Zhang">Yi Zhang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Zhang, Li" sort="Zhang, Li" uniqKey="Zhang L" first="Li" last="Zhang">Li Zhang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Seale, Holly" sort="Seale, Holly" uniqKey="Seale H" first="Holly" last="Seale">Holly Seale</name>
<affiliation><nlm:aff id="aff2"><addr-line>School of Public Health and Community Medicine, UNSW Medicine, The University of New South Wales, Sydney, New South Wales, Australia</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Wang, Quanyi" sort="Wang, Quanyi" uniqKey="Wang Q" first="Quanyi" last="Wang">Quanyi Wang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
</titleStmt>
<publicationStmt><idno type="wicri:source">PMC</idno>
<idno type="pmid">23226380</idno>
<idno type="pmc">3511333</idno>
<idno type="url">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3511333</idno>
<idno type="RBID">PMC:3511333</idno>
<idno type="doi">10.1371/journal.pone.0050770</idno>
<date when="2012">2012</date>
<idno type="wicri:Area/Pmc/Corpus">000B50</idno>
<idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Corpus" wicri:corpus="PMC">000B50</idno>
</publicationStmt>
<sourceDesc><biblStruct><analytic><title xml:lang="en" level="a" type="main">A Serological Survey of Antibodies to H5, H7 and H9 Avian Influenza Viruses amongst the Duck-Related Workers in Beijing, China</title>
<author><name sortKey="Yang, Peng" sort="Yang, Peng" uniqKey="Yang P" first="Peng" last="Yang">Peng Yang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Ma, Chunna" sort="Ma, Chunna" uniqKey="Ma C" first="Chunna" last="Ma">Chunna Ma</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Shi, Weixian" sort="Shi, Weixian" uniqKey="Shi W" first="Weixian" last="Shi">Weixian Shi</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Cui, Shujuan" sort="Cui, Shujuan" uniqKey="Cui S" first="Shujuan" last="Cui">Shujuan Cui</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Lu, Guilan" sort="Lu, Guilan" uniqKey="Lu G" first="Guilan" last="Lu">Guilan Lu</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Peng, Xiaomin" sort="Peng, Xiaomin" uniqKey="Peng X" first="Xiaomin" last="Peng">Xiaomin Peng</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Zhang, Daitao" sort="Zhang, Daitao" uniqKey="Zhang D" first="Daitao" last="Zhang">Daitao Zhang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Liu, Yimeng" sort="Liu, Yimeng" uniqKey="Liu Y" first="Yimeng" last="Liu">Yimeng Liu</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Liang, Huijie" sort="Liang, Huijie" uniqKey="Liang H" first="Huijie" last="Liang">Huijie Liang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Zhang, Yi" sort="Zhang, Yi" uniqKey="Zhang Y" first="Yi" last="Zhang">Yi Zhang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Zhang, Li" sort="Zhang, Li" uniqKey="Zhang L" first="Li" last="Zhang">Li Zhang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Seale, Holly" sort="Seale, Holly" uniqKey="Seale H" first="Holly" last="Seale">Holly Seale</name>
<affiliation><nlm:aff id="aff2"><addr-line>School of Public Health and Community Medicine, UNSW Medicine, The University of New South Wales, Sydney, New South Wales, Australia</addr-line>
</nlm:aff>
</affiliation>
</author>
<author><name sortKey="Wang, Quanyi" sort="Wang, Quanyi" uniqKey="Wang Q" first="Quanyi" last="Wang">Quanyi Wang</name>
<affiliation><nlm:aff id="aff1"><addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</nlm:aff>
</affiliation>
</author>
</analytic>
<series><title level="j">PLoS ONE</title>
<idno type="eISSN">1932-6203</idno>
<imprint><date when="2012">2012</date>
</imprint>
</series>
</biblStruct>
</sourceDesc>
</fileDesc>
<profileDesc><textClass></textClass>
</profileDesc>
</teiHeader>
<front><div type="abstract" xml:lang="en"><p>The continued spread of highly pathogenic avian influenza (HPAI) viruses of H5 and H7 subtypes and low pathogenic avian influenza (LPAI) viruses of H5, H7 and H9 subtypes in birds and the subsequent infections in humans pose an ongoing pandemic threat. It has been proposed that poultry workers are at higher risk of exposure to HPAI or LPAI viruses and subsequently infection due to their repeated exposure to chickens or domestic waterfowl. The aim of this study was to examine the seroprevalence of antibodies against H5, H7 and H9 viruses amongst duck-related workers in Beijing, China and the risk factors associated with seropositivity. In March, 2011, 1741 participants were recruited from (1) commercial duck-breeding farms; (2) private duck-breeding farms; and (3) duck-slaughtering farms. Local villagers who bred ducks in their backyards were also recruited. A survey was administered by face-to-face interview, and blood samples were collected from subjects for antibody testing against H5, H7 and H9 viruses. We found that none of the subjects were seropositive for either H5 or H7 viruses, and only 0.7% (12/1741) had antibody against H9. A statistically significant difference in H9 antibody seroprevalence existed between the various categories of workers (<italic>P</italic>
= 0.005), with the highest figures recorded amongst the villagers (1.7%). Independent risk factors associated with seropositivity toinfection with H9 virus included less frequent disinfection of worksite (OR, 5.13 [95% CI, 1.07–24.58]; <italic>P</italic>
= 0.041; ≤ twice monthly versus>twice monthly) and handling ducks with wounds on hands (OR, 4.13 [95% CI, 1.26–13.57]; <italic>P</italic>
= 0.019). Whilst the risk of infection with H5, H7 and H9 viruses appears to be low among duck-related workers in Beijing, China, ongoing monitoring of infection with the H9 virus is still warranted, especially amongst villagers who breed backyard ducks to monitor for any changes.</p>
</div>
</front>
<back><div1 type="bibliography"><listBibl><biblStruct><analytic><author><name sortKey="Alexander, Dj" uniqKey="Alexander D">DJ Alexander</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Abdel Ghafar, An" uniqKey="Abdel Ghafar A">AN Abdel-Ghafar</name>
</author>
<author><name sortKey="Chotpitayasunondh, T" uniqKey="Chotpitayasunondh T">T Chotpitayasunondh</name>
</author>
<author><name sortKey="Gao, Z" uniqKey="Gao Z">Z Gao</name>
</author>
<author><name sortKey="Hayden, Fg" uniqKey="Hayden F">FG Hayden</name>
</author>
<author><name sortKey="Nguyen, Dh" uniqKey="Nguyen D">DH Nguyen</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Kurtz, J" uniqKey="Kurtz J">J Kurtz</name>
</author>
<author><name sortKey="Manvell, Rj" uniqKey="Manvell R">RJ Manvell</name>
</author>
<author><name sortKey="Banks, J" uniqKey="Banks J">J Banks</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Koopmans, M" uniqKey="Koopmans M">M Koopmans</name>
</author>
<author><name sortKey="Wilbrink, B" uniqKey="Wilbrink B">B Wilbrink</name>
</author>
<author><name sortKey="Conyn, M" uniqKey="Conyn M">M Conyn</name>
</author>
<author><name sortKey="Natrop, G" uniqKey="Natrop G">G Natrop</name>
</author>
<author><name sortKey="Van Der Nat, H" uniqKey="Van Der Nat H">H van der Nat</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Fouchier, Ra" uniqKey="Fouchier R">RA Fouchier</name>
</author>
<author><name sortKey="Schneeberger, Pm" uniqKey="Schneeberger P">PM Schneeberger</name>
</author>
<author><name sortKey="Rozendaal, Fw" uniqKey="Rozendaal F">FW Rozendaal</name>
</author>
<author><name sortKey="Broekman, Jm" uniqKey="Broekman J">JM Broekman</name>
</author>
<author><name sortKey="Kemink, Sa" uniqKey="Kemink S">SA Kemink</name>
</author>
</analytic>
</biblStruct>
<biblStruct></biblStruct>
<biblStruct><analytic><author><name sortKey="Guo, Y" uniqKey="Guo Y">Y Guo</name>
</author>
<author><name sortKey="Li, J" uniqKey="Li J">J Li</name>
</author>
<author><name sortKey="Cheng, X" uniqKey="Cheng X">X Cheng</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Guo, Y" uniqKey="Guo Y">Y Guo</name>
</author>
<author><name sortKey="Xie, J" uniqKey="Xie J">J Xie</name>
</author>
<author><name sortKey="Wang, M" uniqKey="Wang M">M Wang</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Peiris, M" uniqKey="Peiris M">M Peiris</name>
</author>
<author><name sortKey="Yuen, Ky" uniqKey="Yuen K">KY Yuen</name>
</author>
<author><name sortKey="Leung, Cw" uniqKey="Leung C">CW Leung</name>
</author>
<author><name sortKey="Chan, Kh" uniqKey="Chan K">KH Chan</name>
</author>
<author><name sortKey="Ip, Pl" uniqKey="Ip P">PL Ip</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Butt, Km" uniqKey="Butt K">KM Butt</name>
</author>
<author><name sortKey="Smith, Gj" uniqKey="Smith G">GJ Smith</name>
</author>
<author><name sortKey="Chen, H" uniqKey="Chen H">H Chen</name>
</author>
<author><name sortKey="Zhang, Lj" uniqKey="Zhang L">LJ Zhang</name>
</author>
<author><name sortKey="Leung, Yh" uniqKey="Leung Y">YH Leung</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Lin, Yp" uniqKey="Lin Y">YP Lin</name>
</author>
<author><name sortKey="Shaw, M" uniqKey="Shaw M">M Shaw</name>
</author>
<author><name sortKey="Gregory, V" uniqKey="Gregory V">V Gregory</name>
</author>
<author><name sortKey="Cameron, K" uniqKey="Cameron K">K Cameron</name>
</author>
<author><name sortKey="Lim, W" uniqKey="Lim W">W Lim</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Reid, Ah" uniqKey="Reid A">AH Reid</name>
</author>
<author><name sortKey="Fanning, Tg" uniqKey="Fanning T">TG Fanning</name>
</author>
<author><name sortKey="Hultin, Jv" uniqKey="Hultin J">JV Hultin</name>
</author>
<author><name sortKey="Taubenberger, Jk" uniqKey="Taubenberger J">JK Taubenberger</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Schafer, Jr" uniqKey="Schafer J">JR Schafer</name>
</author>
<author><name sortKey="Kawaoka, Y" uniqKey="Kawaoka Y">Y Kawaoka</name>
</author>
<author><name sortKey="Bean, Wj" uniqKey="Bean W">WJ Bean</name>
</author>
<author><name sortKey="Suss, J" uniqKey="Suss J">J Suss</name>
</author>
<author><name sortKey="Senne, D" uniqKey="Senne D">D Senne</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Scholtissek, C" uniqKey="Scholtissek C">C Scholtissek</name>
</author>
<author><name sortKey="Rohde, W" uniqKey="Rohde W">W Rohde</name>
</author>
<author><name sortKey="Von Hoyningen, V" uniqKey="Von Hoyningen V">V Von Hoyningen</name>
</author>
<author><name sortKey="Rott, R" uniqKey="Rott R">R Rott</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Dawood, Fs" uniqKey="Dawood F">FS Dawood</name>
</author>
<author><name sortKey="Jain, S" uniqKey="Jain S">S Jain</name>
</author>
<author><name sortKey="Finelli, L" uniqKey="Finelli L">L Finelli</name>
</author>
<author><name sortKey="Shaw, Mw" uniqKey="Shaw M">MW Shaw</name>
</author>
<author><name sortKey="Lindstrom, S" uniqKey="Lindstrom S">S Lindstrom</name>
</author>
</analytic>
</biblStruct>
<biblStruct></biblStruct>
<biblStruct><analytic><author><name sortKey="Zhou, L" uniqKey="Zhou L">L Zhou</name>
</author>
<author><name sortKey="Liao, Q" uniqKey="Liao Q">Q Liao</name>
</author>
<author><name sortKey="Dong, L" uniqKey="Dong L">L Dong</name>
</author>
<author><name sortKey="Huai, Y" uniqKey="Huai Y">Y Huai</name>
</author>
<author><name sortKey="Bai, T" uniqKey="Bai T">T Bai</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Cavailler, P" uniqKey="Cavailler P">P Cavailler</name>
</author>
<author><name sortKey="Chu, S" uniqKey="Chu S">S Chu</name>
</author>
<author><name sortKey="Ly, S" uniqKey="Ly S">S Ly</name>
</author>
<author><name sortKey="Garcia, Jm" uniqKey="Garcia J">JM Garcia</name>
</author>
<author><name sortKey="Ha Do, Q" uniqKey="Ha Do Q">Q Ha do</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Van Kerkhove, Md" uniqKey="Van Kerkhove M">MD Van Kerkhove</name>
</author>
<author><name sortKey="Ly, S" uniqKey="Ly S">S Ly</name>
</author>
<author><name sortKey="Holl, D" uniqKey="Holl D">D Holl</name>
</author>
<author><name sortKey="Guitian, J" uniqKey="Guitian J">J Guitian</name>
</author>
<author><name sortKey="Mangtani, P" uniqKey="Mangtani P">P Mangtani</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Dinh, Pn" uniqKey="Dinh P">PN Dinh</name>
</author>
<author><name sortKey="Long, Ht" uniqKey="Long H">HT Long</name>
</author>
<author><name sortKey="Tien, Nt" uniqKey="Tien N">NT Tien</name>
</author>
<author><name sortKey="Hien, Nt" uniqKey="Hien N">NT Hien</name>
</author>
<author><name sortKey="Mai Le, Tq" uniqKey="Mai Le T">TQ Mai le</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Vong, S" uniqKey="Vong S">S Vong</name>
</author>
<author><name sortKey="Ly, S" uniqKey="Ly S">S Ly</name>
</author>
<author><name sortKey="Van Kerkhove, Md" uniqKey="Van Kerkhove M">MD Van Kerkhove</name>
</author>
<author><name sortKey="Achenbach, J" uniqKey="Achenbach J">J Achenbach</name>
</author>
<author><name sortKey="Holl, D" uniqKey="Holl D">D Holl</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Mounts, Aw" uniqKey="Mounts A">AW Mounts</name>
</author>
<author><name sortKey="Kwong, H" uniqKey="Kwong H">H Kwong</name>
</author>
<author><name sortKey="Izurieta, Hs" uniqKey="Izurieta H">HS Izurieta</name>
</author>
<author><name sortKey="Ho, Y" uniqKey="Ho Y">Y Ho</name>
</author>
<author><name sortKey="Au, T" uniqKey="Au T">T Au</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Shortridge, Kf" uniqKey="Shortridge K">KF Shortridge</name>
</author>
<author><name sortKey="Stuart Harris, Ch" uniqKey="Stuart Harris C">CH Stuart-Harris</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Kayali, G" uniqKey="Kayali G">G Kayali</name>
</author>
<author><name sortKey="Setterquist, Sf" uniqKey="Setterquist S">SF Setterquist</name>
</author>
<author><name sortKey="Capuano, Aw" uniqKey="Capuano A">AW Capuano</name>
</author>
<author><name sortKey="Myers, Kp" uniqKey="Myers K">KP Myers</name>
</author>
<author><name sortKey="Gill, Js" uniqKey="Gill J">JS Gill</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Pawar, Sd" uniqKey="Pawar S">SD Pawar</name>
</author>
<author><name sortKey="Tandale, Bv" uniqKey="Tandale B">BV Tandale</name>
</author>
<author><name sortKey="Raut, Cg" uniqKey="Raut C">CG Raut</name>
</author>
<author><name sortKey="Parkhi, Ss" uniqKey="Parkhi S">SS Parkhi</name>
</author>
<author><name sortKey="Barde, Td" uniqKey="Barde T">TD Barde</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Meijer, A" uniqKey="Meijer A">A Meijer</name>
</author>
<author><name sortKey="Bosman, A" uniqKey="Bosman A">A Bosman</name>
</author>
<author><name sortKey="Van De Kamp, Ee" uniqKey="Van De Kamp E">EE van de Kamp</name>
</author>
<author><name sortKey="Wilbrink, B" uniqKey="Wilbrink B">B Wilbrink</name>
</author>
<author><name sortKey="Du Ry Van Beest Holle, M" uniqKey="Du Ry Van Beest Holle M">M Du Ry van Beest Holle</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Martin, V" uniqKey="Martin V">V Martin</name>
</author>
<author><name sortKey="Pfeiffer, Du" uniqKey="Pfeiffer D">DU Pfeiffer</name>
</author>
<author><name sortKey="Zhou, X" uniqKey="Zhou X">X Zhou</name>
</author>
<author><name sortKey="Xiao, X" uniqKey="Xiao X">X Xiao</name>
</author>
<author><name sortKey="Prosser, Dj" uniqKey="Prosser D">DJ Prosser</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Huo, X" uniqKey="Huo X">X Huo</name>
</author>
<author><name sortKey="Zu, R" uniqKey="Zu R">R Zu</name>
</author>
<author><name sortKey="Qi, X" uniqKey="Qi X">X Qi</name>
</author>
<author><name sortKey="Qin, Y" uniqKey="Qin Y">Y Qin</name>
</author>
<author><name sortKey="Li, L" uniqKey="Li L">L Li</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Wang, M" uniqKey="Wang M">M Wang</name>
</author>
<author><name sortKey="Fu, Cx" uniqKey="Fu C">CX Fu</name>
</author>
<author><name sortKey="Zheng, Bj" uniqKey="Zheng B">BJ Zheng</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Schultsz, C" uniqKey="Schultsz C">C Schultsz</name>
</author>
<author><name sortKey="Nguyen, Vd" uniqKey="Nguyen V">VD Nguyen</name>
</author>
<author><name sortKey="Hai Le, T" uniqKey="Hai Le T">T Hai le</name>
</author>
<author><name sortKey="Do, Qh" uniqKey="Do Q">QH Do</name>
</author>
<author><name sortKey="Peiris, Js" uniqKey="Peiris J">JS Peiris</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Hinjoy, S" uniqKey="Hinjoy S">S Hinjoy</name>
</author>
<author><name sortKey="Puthavathana, P" uniqKey="Puthavathana P">P Puthavathana</name>
</author>
<author><name sortKey="Laosiritaworn, Y" uniqKey="Laosiritaworn Y">Y Laosiritaworn</name>
</author>
<author><name sortKey="Limpakarnjanarat, K" uniqKey="Limpakarnjanarat K">K Limpakarnjanarat</name>
</author>
<author><name sortKey="Pooruk, P" uniqKey="Pooruk P">P Pooruk</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Vong, S" uniqKey="Vong S">S Vong</name>
</author>
<author><name sortKey="Coghlan, B" uniqKey="Coghlan B">B Coghlan</name>
</author>
<author><name sortKey="Mardy, S" uniqKey="Mardy S">S Mardy</name>
</author>
<author><name sortKey="Holl, D" uniqKey="Holl D">D Holl</name>
</author>
<author><name sortKey="Seng, H" uniqKey="Seng H">H Seng</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Jia, N" uniqKey="Jia N">N Jia</name>
</author>
<author><name sortKey="De Vlas, Sj" uniqKey="De Vlas S">SJ de Vlas</name>
</author>
<author><name sortKey="Liu, Yx" uniqKey="Liu Y">YX Liu</name>
</author>
<author><name sortKey="Zhang, Js" uniqKey="Zhang J">JS Zhang</name>
</author>
<author><name sortKey="Zhan, L" uniqKey="Zhan L">L Zhan</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Woo, Jt" uniqKey="Woo J">JT Woo</name>
</author>
<author><name sortKey="Park, Bk" uniqKey="Park B">BK Park</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Ji, K" uniqKey="Ji K">K Ji</name>
</author>
<author><name sortKey="Jiang, Wm" uniqKey="Jiang W">WM Jiang</name>
</author>
<author><name sortKey="Liu, S" uniqKey="Liu S">S Liu</name>
</author>
<author><name sortKey="Chen, Jm" uniqKey="Chen J">JM Chen</name>
</author>
<author><name sortKey="Chen, J" uniqKey="Chen J">J Chen</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Zhang, Y" uniqKey="Zhang Y">Y Zhang</name>
</author>
<author><name sortKey="Yin, Y" uniqKey="Yin Y">Y Yin</name>
</author>
<author><name sortKey="Bi, Y" uniqKey="Bi Y">Y Bi</name>
</author>
<author><name sortKey="Wang, S" uniqKey="Wang S">S Wang</name>
</author>
<author><name sortKey="Xu, S" uniqKey="Xu S">S Xu</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Jia, N" uniqKey="Jia N">N Jia</name>
</author>
<author><name sortKey="Wang, Sx" uniqKey="Wang S">SX Wang</name>
</author>
<author><name sortKey="Liu, Yx" uniqKey="Liu Y">YX Liu</name>
</author>
<author><name sortKey="Zhang, Ph" uniqKey="Zhang P">PH Zhang</name>
</author>
<author><name sortKey="Zuo, Sq" uniqKey="Zuo S">SQ Zuo</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Ito, T" uniqKey="Ito T">T Ito</name>
</author>
<author><name sortKey="Suzuki, Y" uniqKey="Suzuki Y">Y Suzuki</name>
</author>
<author><name sortKey="Mitnaul, L" uniqKey="Mitnaul L">L Mitnaul</name>
</author>
<author><name sortKey="Vines, A" uniqKey="Vines A">A Vines</name>
</author>
<author><name sortKey="Kida, H" uniqKey="Kida H">H Kida</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Stephenson, I" uniqKey="Stephenson I">I Stephenson</name>
</author>
<author><name sortKey="Wood, Jm" uniqKey="Wood J">JM Wood</name>
</author>
<author><name sortKey="Nicholson, Kg" uniqKey="Nicholson K">KG Nicholson</name>
</author>
<author><name sortKey="Zambon, Mc" uniqKey="Zambon M">MC Zambon</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Olsen, B" uniqKey="Olsen B">B Olsen</name>
</author>
<author><name sortKey="Munster, Vj" uniqKey="Munster V">VJ Munster</name>
</author>
<author><name sortKey="Wallensten, A" uniqKey="Wallensten A">A Wallensten</name>
</author>
<author><name sortKey="Waldenstrom, J" uniqKey="Waldenstrom J">J Waldenstrom</name>
</author>
<author><name sortKey="Osterhaus, Ad" uniqKey="Osterhaus A">AD Osterhaus</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Gill, Js" uniqKey="Gill J">JS Gill</name>
</author>
<author><name sortKey="Webby, R" uniqKey="Webby R">R Webby</name>
</author>
<author><name sortKey="Gilchrist, Mj" uniqKey="Gilchrist M">MJ Gilchrist</name>
</author>
<author><name sortKey="Gray, Gc" uniqKey="Gray G">GC Gray</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Li, Y" uniqKey="Li Y">Y Li</name>
</author>
<author><name sortKey="Shi, J" uniqKey="Shi J">J Shi</name>
</author>
<author><name sortKey="Zhong, G" uniqKey="Zhong G">G Zhong</name>
</author>
<author><name sortKey="Deng, G" uniqKey="Deng G">G Deng</name>
</author>
<author><name sortKey="Tian, G" uniqKey="Tian G">G Tian</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Kim, Hr" uniqKey="Kim H">HR Kim</name>
</author>
<author><name sortKey="Lee, Yj" uniqKey="Lee Y">YJ Lee</name>
</author>
<author><name sortKey="Park, Ck" uniqKey="Park C">CK Park</name>
</author>
<author><name sortKey="Oem, Jk" uniqKey="Oem J">JK Oem</name>
</author>
<author><name sortKey="Lee, Os" uniqKey="Lee O">OS Lee</name>
</author>
</analytic>
</biblStruct>
<biblStruct><analytic><author><name sortKey="Kou, Z" uniqKey="Kou Z">Z Kou</name>
</author>
<author><name sortKey="Li, Y" uniqKey="Li Y">Y Li</name>
</author>
<author><name sortKey="Yin, Z" uniqKey="Yin Z">Z Yin</name>
</author>
<author><name sortKey="Guo, S" uniqKey="Guo S">S Guo</name>
</author>
<author><name sortKey="Wang, M" uniqKey="Wang M">M Wang</name>
</author>
</analytic>
</biblStruct>
</listBibl>
</div1>
</back>
</TEI>
<pmc article-type="research-article"><pmc-dir>properties open_access</pmc-dir>
<front><journal-meta><journal-id journal-id-type="nlm-ta">PLoS One</journal-id>
<journal-id journal-id-type="iso-abbrev">PLoS ONE</journal-id>
<journal-id journal-id-type="publisher-id">plos</journal-id>
<journal-id journal-id-type="pmc">plosone</journal-id>
<journal-title-group><journal-title>PLoS ONE</journal-title>
</journal-title-group>
<issn pub-type="epub">1932-6203</issn>
<publisher><publisher-name>Public Library of Science</publisher-name>
<publisher-loc>San Francisco, USA</publisher-loc>
</publisher>
</journal-meta>
<article-meta><article-id pub-id-type="pmid">23226380</article-id>
<article-id pub-id-type="pmc">3511333</article-id>
<article-id pub-id-type="publisher-id">PONE-D-12-23269</article-id>
<article-id pub-id-type="doi">10.1371/journal.pone.0050770</article-id>
<article-categories><subj-group subj-group-type="heading"><subject>Research Article</subject>
</subj-group>
<subj-group subj-group-type="Discipline-v2"><subject>Biology</subject>
<subj-group><subject>Population Biology</subject>
<subj-group><subject>Epidemiology</subject>
<subj-group><subject>Infectious Disease Epidemiology</subject>
</subj-group>
</subj-group>
</subj-group>
</subj-group>
<subj-group subj-group-type="Discipline-v2"><subject>Medicine</subject>
<subj-group><subject>Epidemiology</subject>
<subj-group><subject>Infectious Disease Epidemiology</subject>
</subj-group>
</subj-group>
<subj-group><subject>Global Health</subject>
</subj-group>
<subj-group><subject>Infectious diseases</subject>
<subj-group><subject>Zoonoses</subject>
<subj-group><subject>Avian influenza A viruses</subject>
</subj-group>
</subj-group>
</subj-group>
<subj-group><subject>Public Health</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group><article-title>A Serological Survey of Antibodies to H5, H7 and H9 Avian Influenza Viruses amongst the Duck-Related Workers in Beijing, China</article-title>
<alt-title alt-title-type="running-head">Antibodies to H5, H7 and H9 in Duck Workers</alt-title>
</title-group>
<contrib-group><contrib contrib-type="author"><name><surname>Yang</surname>
<given-names>Peng</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Ma</surname>
<given-names>Chunna</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Shi</surname>
<given-names>Weixian</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Cui</surname>
<given-names>Shujuan</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Lu</surname>
<given-names>Guilan</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Peng</surname>
<given-names>Xiaomin</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Zhang</surname>
<given-names>Daitao</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Liu</surname>
<given-names>Yimeng</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Liang</surname>
<given-names>Huijie</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Zhang</surname>
<given-names>Yi</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Zhang</surname>
<given-names>Li</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Seale</surname>
<given-names>Holly</given-names>
</name>
<xref ref-type="aff" rid="aff2"><sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Wang</surname>
<given-names>Quanyi</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup>
</xref>
<xref ref-type="corresp" rid="cor1"><sup>*</sup>
</xref>
</contrib>
</contrib-group>
<aff id="aff1"><label>1</label>
<addr-line>Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control (CDC), Beijing, China</addr-line>
</aff>
<aff id="aff2"><label>2</label>
<addr-line>School of Public Health and Community Medicine, UNSW Medicine, The University of New South Wales, Sydney, New South Wales, Australia</addr-line>
</aff>
<contrib-group><contrib contrib-type="editor"><name><surname>Brown</surname>
<given-names>Justin David</given-names>
</name>
<role>Editor</role>
<xref ref-type="aff" rid="edit1"></xref>
</contrib>
</contrib-group>
<aff id="edit1"><addr-line>University of Georgia, United States of America</addr-line>
</aff>
<author-notes><corresp id="cor1">* E-mail: <email>bjcdcxm@126.com</email>
</corresp>
<fn fn-type="COI-statement"><p><bold>Competing Interests: </bold>
The authors have declared that no competing interests exist.</p>
</fn>
<fn fn-type="con"><p>Conceived and designed the experiments: QW PY. Performed the experiments: QW PY CM WS SC GL XP HL. Analyzed the data: PY CM YZ LZ. Contributed reagents/materials/analysis tools: WS SC DZ YL. Wrote the paper: QW PY. Critical revision of the manuscript for important intellectual content: HS.</p>
</fn>
</author-notes>
<pub-date pub-type="collection"><year>2012</year>
</pub-date>
<pub-date pub-type="epub"><day>30</day>
<month>11</month>
<year>2012</year>
</pub-date>
<volume>7</volume>
<issue>11</issue>
<elocation-id>e50770</elocation-id>
<history><date date-type="received"><day>2</day>
<month>8</month>
<year>2012</year>
</date>
<date date-type="accepted"><day>24</day>
<month>10</month>
<year>2012</year>
</date>
</history>
<permissions><copyright-statement>© 2012 Yang et al</copyright-statement>
<copyright-year>2012</copyright-year>
<copyright-holder>Yang et al</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/"><license-p>This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.</license-p>
</license>
</permissions>
<abstract><p>The continued spread of highly pathogenic avian influenza (HPAI) viruses of H5 and H7 subtypes and low pathogenic avian influenza (LPAI) viruses of H5, H7 and H9 subtypes in birds and the subsequent infections in humans pose an ongoing pandemic threat. It has been proposed that poultry workers are at higher risk of exposure to HPAI or LPAI viruses and subsequently infection due to their repeated exposure to chickens or domestic waterfowl. The aim of this study was to examine the seroprevalence of antibodies against H5, H7 and H9 viruses amongst duck-related workers in Beijing, China and the risk factors associated with seropositivity. In March, 2011, 1741 participants were recruited from (1) commercial duck-breeding farms; (2) private duck-breeding farms; and (3) duck-slaughtering farms. Local villagers who bred ducks in their backyards were also recruited. A survey was administered by face-to-face interview, and blood samples were collected from subjects for antibody testing against H5, H7 and H9 viruses. We found that none of the subjects were seropositive for either H5 or H7 viruses, and only 0.7% (12/1741) had antibody against H9. A statistically significant difference in H9 antibody seroprevalence existed between the various categories of workers (<italic>P</italic>
= 0.005), with the highest figures recorded amongst the villagers (1.7%). Independent risk factors associated with seropositivity toinfection with H9 virus included less frequent disinfection of worksite (OR, 5.13 [95% CI, 1.07–24.58]; <italic>P</italic>
= 0.041; ≤ twice monthly versus>twice monthly) and handling ducks with wounds on hands (OR, 4.13 [95% CI, 1.26–13.57]; <italic>P</italic>
= 0.019). Whilst the risk of infection with H5, H7 and H9 viruses appears to be low among duck-related workers in Beijing, China, ongoing monitoring of infection with the H9 virus is still warranted, especially amongst villagers who breed backyard ducks to monitor for any changes.</p>
</abstract>
<funding-group><funding-statement>This work was supported by the Beijing Nova Program (2011047) of Beijing Science and Technology Commission (<ext-link ext-link-type="uri" xlink:href="http://www.bjkw.gov.cn">http://www.bjkw.gov.cn</ext-link>
) and the National Key Program for Infectious Disease of China (2012ZX10004215-003-001) of Chinese Ministry of Science and Technology (<ext-link ext-link-type="uri" xlink:href="http://www.most.gov.cn/">http://www.most.gov.cn/</ext-link>
). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.</funding-statement>
</funding-group>
<counts><page-count count="7"></page-count>
</counts>
</article-meta>
</front>
<body><sec id="s1"><title>Introduction</title>
<p>The spread of highly pathogenic avian influenza (HPAI) viruses of H5 or H7 subtypes and low pathogenic avian influenza (LPAI) viruses of H5, H7 or H9 subtypes amongst birds and sporadic infection in humans continues to pose a threat to public health <xref rid="pone.0050770-Alexander1" ref-type="bibr">[1]</xref>
–<xref rid="pone.0050770-Butt1" ref-type="bibr">[10]</xref>
, because of the potential for a strain with pandemic potential to emerge via adaptive mutation or reassortment <xref rid="pone.0050770-Lin1" ref-type="bibr">[11]</xref>
. The 1918 pandemic begun following adaptive mutation of an avian virus, and the pandemics of 1957 and 1968 were the result of genetic reassortment of viruses from human and avian sources <xref rid="pone.0050770-Reid1" ref-type="bibr">[12]</xref>
–<xref rid="pone.0050770-Scholtissek1" ref-type="bibr">[14]</xref>
. While the last pandemic originated from a swine-origin influenza virus (S-OIV) <xref rid="pone.0050770-Dawood1" ref-type="bibr">[15]</xref>
, the threat brought by avian influenza viruses continues.</p>
<p>As of September, 2012, a total of 608 human cases of HPAI H5N1 were reported globally, with a case-fatality ratio of 59.0% (359 fatal cases) <xref rid="pone.0050770-World1" ref-type="bibr">[16]</xref>
. In addition, human cases infected with H7 or H9 viruses were also sporadically reported in a couple of countries. In 1996, a woman developed conjunctivitis after a piece of straw had entered her eye while cleaning her duck house, with LPAI H7N7 virus isolated from her conjunctiva specimen <xref rid="pone.0050770-Kurtz1" ref-type="bibr">[3]</xref>
. In 2003, 89 people were confirmed as being infected with HPAI H7N7 in the Netherlands with evidence of limited person to person transmission, which was associated with an outbreak of HPAI H7N7 in chickens in over 200 farms <xref rid="pone.0050770-Koopmans1" ref-type="bibr">[4]</xref>
, <xref rid="pone.0050770-Fouchier1" ref-type="bibr">[5]</xref>
. In 2007, four cases infected with LPAI H7N2 were identified after an outbreak of LPAI H7N2 in chickens on a small farm in north Wales in the United Kingdom <xref rid="pone.0050770-Editorial1" ref-type="bibr">[6]</xref>
. Eight cases were confirmed as being infected with LPAI H9N2 from mainland and Hong Kong, China in 1998–1999, of which three had contact with live chickens before illness onset <xref rid="pone.0050770-Guo1" ref-type="bibr">[7]</xref>
–<xref rid="pone.0050770-Peiris1" ref-type="bibr">[9]</xref>
. In 2003, a five-year-old child infected with LPAI H9N2 was reported in Hong Kong, China. However, the source of infection was unknown <xref rid="pone.0050770-Butt1" ref-type="bibr">[10]</xref>
.</p>
<p>To date most studies, especially those on risk factors of infection, have generally focused on H5 virus rather than H7 or H9 viruses <xref rid="pone.0050770-Zhou1" ref-type="bibr">[17]</xref>
–<xref rid="pone.0050770-Mounts1" ref-type="bibr">[22]</xref>
. Given the distinct possibility of human infection with H7 or H9 viruses and the minimal human-to-human transmission of avian-adapted viruses, it is important that the research focus shift accordingly. Previous studies have demonstrated that both direct and indirect exposure to infected live/dead poultry, including chickens or domestic waterfowl, plays a very important role in the transmission of HPAI or LPAI viruses to human <xref rid="pone.0050770-Kurtz1" ref-type="bibr">[3]</xref>
–<xref rid="pone.0050770-Guo1" ref-type="bibr">[7]</xref>
, <xref rid="pone.0050770-Zhou1" ref-type="bibr">[17]</xref>
, <xref rid="pone.0050770-Dinh1" ref-type="bibr">[20]</xref>
, <xref rid="pone.0050770-Mounts1" ref-type="bibr">[22]</xref>
. Poultry workers are therefore considered to be at highest risk of infection with HPAI or LPAI viruses because of their frequent exposure to chickens or domestic waterfowl. In addition, as China is considered to be an an influenza epicenter <xref rid="pone.0050770-Shortridge1" ref-type="bibr">[23]</xref>
, ongoing monitoring of infection from HPAI or LPAI viruses in China is warranted.</p>
<p>In this study, we conducted a serological survey of antibodies against H5, H7 and H9 viruses amongst duck-related workers in Beijing, China to examine previous infection with these viruses and associated risk factors in this population.</p>
</sec>
<sec sec-type="materials|methods" id="s2"><title>Materials and Methods</title>
<sec id="s2a"><title>Ethics Statement</title>
<p>This study was approved by the institutional review board and human research ethics committee of Beijing Center for Disease Prevention and Control (CDC).</p>
</sec>
<sec id="s2b"><title>Subjects and Survey Design</title>
<p>This study was conducted in Beijing, China in March, 2011. In Beijing, 14 of the 18 districts are classified as having some form of duck-related industry. 6/14 districts were randomly selected for inclusion in the study. Workers from commercial and private duck-breeding farms and slaughtering sites were invited to participate in this study. Local villagers involved with breeding ducks in their backyards were also recruited. A duck-slaughtering site refers to a place where ducks are killed, phlebotomized, plucked, the heads/viscera removed, and processed ducks are cleaned and packaged. Workers were excluded if they were employed in a position in which exposure to ducks was limited such as those in administrative roles. From the selected six districts, all identified workers who were employed within the sector and households involved with breeding ducks in their backyards were invited to participate in this study. From each household, one family member who was deemed to have the closest contact with ducks was recruited in this study.</p>
<p>After obtaining written informed consent from the participants, a questionnaire was administered via a face-to-face interview conducted by trained staffs, and blood samples were collected for antibody testing against H5, H7 and H9 viruses.</p>
</sec>
<sec id="s2c"><title>Survey Contents</title>
<p>The survey included questions on employment, demographics (sex, age, and education background), presence of any underlying disease, smoking, and alcohol intake. Other items included duration of exposure to ducks, farming practices (e.g. breeding patterns, duck breeds), avian influenza vaccination status of the ducks, exposure of ducks to other species of birds, disinfection of worksite, personal protective equipment use, handling ducks with wounds on hands and contact with sick or dead ducks, etc.</p>
</sec>
<sec id="s2d"><title>Laboratory Testing</title>
<p>Serum samples were pretreated and assayed by hemagglutination-inhibition (HI) assay, as previously described <xref rid="pone.0050770-Kayali1" ref-type="bibr">[24]</xref>
. One volume of serum was treated with four volumes of receptor-destroying enzyme (RDE) at 37°C for 18 hours, and was then incubated at 56°C for 30 minutes, followed by absorption with horse erythrocytes. The titration of 1∶10 was first prepared for each pre-treated serum sample to test for specific antibodies against H5, H7 and H9 virus antigens using 1% horse erythrocytes. H5, H7 and H9 virus antigens employed for HI assay were A/Chicken/Anhui/01/2005 (HPAI H5N1), A/Chicken/Hebei/02/2007(LPAI H7N2) and A/Chicken/Shanghai/10/1999 (LPAI H9N2), provided by Qingdao YEBIO Bio-engineering Co.,Ltd, China. The serum samples with 1∶10 titer that were able to inhibit virus-induced hemagglutination were then diluted into eight titrations (1∶10, 1∶20, 1∶40, 1∶80, 1∶160, 1∶320, 1∶640 and 1∶1280) for the HI assay. The HI titer was calculated as the reciprocal of the highest dilution of serum that inhibited virus-induced hemagglutination of the horse erythrocytes. A titer value of ≥1∶40 was regarded as positive, i.e. previous infection <xref rid="pone.0050770-Pawar1" ref-type="bibr">[25]</xref>
, <xref rid="pone.0050770-Meijer1" ref-type="bibr">[26]</xref>
.</p>
</sec>
<sec id="s2e"><title>Statistical Analysis</title>
<p>Data were entered in duplicate using EpiData Software, and was analyzed using SPSS16.0 statistical package (SPSS Inc., Chicago, IL, USA). We estimated the seroprevalence rates of antibodies against H5, H7 and H9 viruses among various types of subjects. Seroprevalence rates were compared between subgroups using Pearson χ<sup>2</sup>
test. Seropositive (HI titer≥1∶40) and seronegative (HI titer<1∶40) groups were compared to identify potential risk factors associated with seropositivity to H5, H7 or H9 viruses (previous infection), and univariate and multivariate unconditional logistic regression analysis were conducted to determine risk factors. The variables with <italic>P</italic>
<0.10 in univariate analysis were included in multivariate analysis. Backward logistic regression was conducted with a probability of removal set at 0.1, i.e. all variables with p<0.10 were left in the final model. All the tests were 2-sided, and statistical significance was defined as <italic>P</italic>
<0.05.</p>
</sec>
</sec>
<sec id="s3"><title>Results</title>
<sec id="s3a"><title>Characteristics of Subjects</title>
<p>A total of 1741 subjects, with the median of age of 44 years (range: 14–71 years), were involved in this study, including 313/374 (response rate: 83.7%) participants from the commercial duck-breeding farms, 261/286 (response rate: 91.3%) from private duck-breeding farms, 562/620 (response rate: 90.6%) from farms which slaughtered ducks, and 605/710 (response rate: 85.2%) villagers who bred backyard ducks. The participant demographic information is summarized in <xref ref-type="table" rid="pone-0050770-t001">Table 1</xref>
.</p>
<table-wrap id="pone-0050770-t001" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0050770.t001</object-id>
<label>Table 1</label>
<caption><title>Baseline characteristics of study participants (n = 1741).</title>
</caption>
<alternatives><graphic id="pone-0050770-t001-1" xlink:href="pone.0050770.t001"></graphic>
<table frame="hsides" rules="groups"><colgroup span="1"><col align="left" span="1"></col>
<col align="center" span="1"></col>
</colgroup>
<thead><tr><td align="left" rowspan="1" colspan="1">Characteristic</td>
<td align="left" rowspan="1" colspan="1">Frequency (% of total)</td>
</tr>
</thead>
<tbody><tr><td align="left" rowspan="1" colspan="1">Participant category</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Commercial duck-breeders</td>
<td align="left" rowspan="1" colspan="1">313 (18.0)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Private duck-breeders</td>
<td align="left" rowspan="1" colspan="1">261 (15.0)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Villagers breeding backyard ducks</td>
<td align="left" rowspan="1" colspan="1">605 (34.7)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Duck-slaughtering workers</td>
<td align="left" rowspan="1" colspan="1">562 (32.3)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Sex</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Male</td>
<td align="left" rowspan="1" colspan="1">759 (43.6)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Female</td>
<td align="left" rowspan="1" colspan="1">982 (56.4)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Age group</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">≤50 years</td>
<td align="left" rowspan="1" colspan="1">1191 (68.4)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">>50 years</td>
<td align="left" rowspan="1" colspan="1">550 (31.6)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Ethnic group</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Chinese Han</td>
<td align="left" rowspan="1" colspan="1">1637 (94.0)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Chinese Minority Groups</td>
<td align="left" rowspan="1" colspan="1">104 (6.0)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Education background</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">>Primary school</td>
<td align="left" rowspan="1" colspan="1">972 (55.8)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">≤Primary school</td>
<td align="left" rowspan="1" colspan="1">769 (44.2)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Marital status</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Not married</td>
<td align="left" rowspan="1" colspan="1">207 (11.9)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Married</td>
<td align="left" rowspan="1" colspan="1">1515 (87.0)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Divorced</td>
<td align="left" rowspan="1" colspan="1">6 (0.3)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Widowed</td>
<td align="left" rowspan="1" colspan="1">13 (0.7)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Having underlying disease</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">1592 (91.4)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">149 (8.6)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Currently smoker</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">1266 (72.7)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">475 (27.3)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Currently drinker</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">1208 (69.4)</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">533 (30.6)</td>
</tr>
</tbody>
</table>
</alternatives>
</table-wrap>
</sec>
<sec id="s3b"><title>Antibody Seroprevalence Against H5, H7 or H9 Viruses</title>
<p>In this study, none of the subjects were seropositive for either H5 or H7 antibodies, and only twelve (0.7%, 12/1741) had antibody against H9, among which four had a titer of 1∶80 and eight with a titer of 1∶40. Ten of the villagers were seropositive to H9 (1.7%, 10/605), but none of the commercial duck breeding farmers were positive. There was a statistically significant difference in seroprevalence of antibody against H9 between the various working categories (<italic>P</italic>
= 0.005). No statistically significant difference was found for H9 seroprevalence between the sexes (<italic>P</italic>
= 0.892), but a difference was found between age groups (<italic>P</italic>
= 0.021), with the higher seroprevalence recorded for subjects above 50 years (1.5%, 8/550). The breakdown by group is shown in <xref ref-type="table" rid="pone-0050770-t002">Table 2</xref>
.</p>
<table-wrap id="pone-0050770-t002" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0050770.t002</object-id>
<label>Table 2</label>
<caption><title>Seroprevalences of antibodies to H5, H7 and H9 viruses in duck-related workers in the serological survey in Beijing, China.</title>
</caption>
<alternatives><graphic id="pone-0050770-t002-2" xlink:href="pone.0050770.t002"></graphic>
<table frame="hsides" rules="groups"><colgroup span="1"><col align="left" span="1"></col>
<col align="center" span="1"></col>
<col align="center" span="1"></col>
<col align="center" span="1"></col>
<col align="center" span="1"></col>
<col align="center" span="1"></col>
</colgroup>
<thead><tr><td align="left" rowspan="1" colspan="1">Characteristic</td>
<td align="left" rowspan="1" colspan="1">Subject number</td>
<td align="left" rowspan="1" colspan="1">H5 virus</td>
<td align="left" rowspan="1" colspan="1">H7 virus</td>
<td align="left" rowspan="1" colspan="1">H9 virus</td>
<td align="left" rowspan="1" colspan="1"><italic>P</italic>
value<xref ref-type="table-fn" rid="nt102">a</xref>
</td>
</tr>
</thead>
<tbody><tr><td align="left" rowspan="1" colspan="1">Participant category</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Commercial duck-breeders</td>
<td align="left" rowspan="1" colspan="1">313</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0.005<xref ref-type="table-fn" rid="nt103">b</xref>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Private duck-breeders</td>
<td align="left" rowspan="1" colspan="1">261</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">1 (0.4)</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Villagers breeding backyard ducks</td>
<td align="left" rowspan="1" colspan="1">605</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">10 (1.7)</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Duck-slaughtering workers</td>
<td align="left" rowspan="1" colspan="1">562</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">1 (0.2)</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Sex</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Male</td>
<td align="left" rowspan="1" colspan="1">759</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">5 (0.7)</td>
<td align="left" rowspan="1" colspan="1">0.892<xref ref-type="table-fn" rid="nt103">b</xref>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Female</td>
<td align="left" rowspan="1" colspan="1">982</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">7 (0.7)</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Age group</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">≤50 years</td>
<td align="left" rowspan="1" colspan="1">1191</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">4 (0.3)</td>
<td align="left" rowspan="1" colspan="1">0.021<xref ref-type="table-fn" rid="nt104">c</xref>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">>50 years</td>
<td align="left" rowspan="1" colspan="1">550</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">8 (1.5)</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Total</td>
<td align="left" rowspan="1" colspan="1">1741</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">12 (0.7)</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
</tbody>
</table>
</alternatives>
<table-wrap-foot><fn id="nt101"><label></label>
<p><bold>NOTE.</bold>
Data are seropostive no (%), unless otherwise indicated.</p>
</fn>
<fn id="nt102"><label>a</label>
<p>Comparison of H9 antibody status.</p>
</fn>
<fn id="nt103"><label>b</label>
<p>Compared by Pearson χ<sup>2</sup>
test.</p>
</fn>
<fn id="nt104"><label>c</label>
<p>Compared by Pearson χ<sup>2</sup>
test with continuity correction.</p>
</fn>
</table-wrap-foot>
</table-wrap>
</sec>
<sec id="s3c"><title>Risk Factors Associated with Seropositivity for Antibodies to H9 Virus in Duck-related Workers</title>
<p>In univariate analysis, the following factors were found to be significantly associated with seropositivity for antibodies to H9 virus (<xref ref-type="table" rid="pone-0050770-t003">Table 3</xref>
): older age (odds ratio [OR], 4.38 [95% confidence interval [CI], 1.31–14.61]; <italic>P</italic>
= 0.016; >50 years versus ≤50 years), fewer years of education (OR, 3.83 [95% CI, 1.03–14.18]; <italic>P</italic>
= 0.045; ≤primary school versus above primary school), exposure to ducks ranging on land and river (OR, 3.91 [95% CI, 1.17–13.04]; <italic>P</italic>
= 0.026; versus ranging only on land), exposure to layer ducks (OR, 6.36 [95% CI, 1.72–23.59]; <italic>P</italic>
= 0.006; versus broiler ducks), exposure to ducks in contact with other birds (OR, 3.92 [95% CI, 1.24–12.41]; <italic>P</italic>
= 0.020), less frequent disinfection of worksite (OR, 7.48 [95% CI, 1.63–34.22]; <italic>P</italic>
= 0.010; ≤ twice monthly versus>twice monthly), noncompliance with mask use (OR, 8.06 [95% CI, 1.04–62.55]; <italic>P</italic>
= 0.046) and handling ducks with wounds on hands (OR, 6.33 [95% CI, 2.00–20.09]; <italic>P</italic>
= 0.002).</p>
<table-wrap id="pone-0050770-t003" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0050770.t003</object-id>
<label>Table 3</label>
<caption><title>Univariate analysis for risk factors associated with seropositivity for antibodies to H9 virus amongst duck-related workers, Beijing, China.</title>
</caption>
<alternatives><graphic id="pone-0050770-t003-3" xlink:href="pone.0050770.t003"></graphic>
<table frame="hsides" rules="groups"><colgroup span="1"><col align="left" span="1"></col>
<col align="center" span="1"></col>
<col align="center" span="1"></col>
<col align="center" span="1"></col>
<col align="center" span="1"></col>
</colgroup>
<thead><tr><td align="left" rowspan="1" colspan="1">Factors</td>
<td align="left" rowspan="1" colspan="1">Seropositivity (n = 12)</td>
<td align="left" rowspan="1" colspan="1">Seronegativity (n = 1729)</td>
<td align="left" rowspan="1" colspan="1">OR (95% CI)</td>
<td align="left" rowspan="1" colspan="1"><italic>P</italic>
value<xref ref-type="table-fn" rid="nt106">*</xref>
</td>
</tr>
</thead>
<tbody><tr><td align="left" rowspan="1" colspan="1">Sex</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Male</td>
<td align="left" rowspan="1" colspan="1">5 (41.7)</td>
<td align="left" rowspan="1" colspan="1">754 (43.6)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Female</td>
<td align="left" rowspan="1" colspan="1">7 (58.3)</td>
<td align="left" rowspan="1" colspan="1">975 (56.4)</td>
<td align="left" rowspan="1" colspan="1">1.08 (0.34–3.43)</td>
<td align="left" rowspan="1" colspan="1">0.892</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Age group</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">≤50 years</td>
<td align="left" rowspan="1" colspan="1">4 (33.3)</td>
<td align="left" rowspan="1" colspan="1">1187 (68.7)</td>
<td align="left" rowspan="1" colspan="1"><bold>Reference</bold>
</td>
<td align="left" rowspan="1" colspan="1"><bold>0.016</bold>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">>50 years</td>
<td align="left" rowspan="1" colspan="1">8 (66.7)</td>
<td align="left" rowspan="1" colspan="1">542 (31.3)</td>
<td align="left" rowspan="1" colspan="1"><bold>4.38 (1.31–14.61)</bold>
</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Education background</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">>Primary school</td>
<td align="left" rowspan="1" colspan="1">3 (25.0)</td>
<td align="left" rowspan="1" colspan="1">969 (56.0)</td>
<td align="left" rowspan="1" colspan="1"><bold>Reference</bold>
</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">≤Primary school</td>
<td align="left" rowspan="1" colspan="1">9 (75.0)</td>
<td align="left" rowspan="1" colspan="1">760 (44.0)</td>
<td align="left" rowspan="1" colspan="1"><bold>3.83 (1.03–14.18)</bold>
</td>
<td align="left" rowspan="1" colspan="1"><bold>0.045</bold>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Having underlying disease</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">10 (83.3)</td>
<td align="left" rowspan="1" colspan="1">1582 (91.5)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">2 (16.7)</td>
<td align="left" rowspan="1" colspan="1">147 (8.5)</td>
<td align="left" rowspan="1" colspan="1">2.15 (0.47–9.92)</td>
<td align="left" rowspan="1" colspan="1">0.325</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Currently smoker</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">9 (75.0)</td>
<td align="left" rowspan="1" colspan="1">1257 (72.7)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">3 (25.0)</td>
<td align="left" rowspan="1" colspan="1">472 (27.3)</td>
<td align="left" rowspan="1" colspan="1">0.89 (0.24–3.29)</td>
<td align="left" rowspan="1" colspan="1">0.859</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Currently drinker</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">7 (58.3)</td>
<td align="left" rowspan="1" colspan="1">1201 (69.5)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">5 (41.7)</td>
<td align="left" rowspan="1" colspan="1">528 (30.5)</td>
<td align="left" rowspan="1" colspan="1">1.63 (0.51–5.14)</td>
<td align="left" rowspan="1" colspan="1">0.409</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Years of exposure</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">≤5 years</td>
<td align="left" rowspan="1" colspan="1">9 (75.0)</td>
<td align="left" rowspan="1" colspan="1">1259 (72.8)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">>5 years</td>
<td align="left" rowspan="1" colspan="1">3 (25.0)</td>
<td align="left" rowspan="1" colspan="1">470 (27.2)</td>
<td align="left" rowspan="1" colspan="1">0.89 (0.24–3.31)</td>
<td align="left" rowspan="1" colspan="1">0.866</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Breeding pattern of ducks</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Ranging only on land</td>
<td align="left" rowspan="1" colspan="1">4 (33.3)</td>
<td align="left" rowspan="1" colspan="1">1144 (66.2)</td>
<td align="left" rowspan="1" colspan="1"><bold>Reference</bold>
</td>
<td align="left" rowspan="1" colspan="1"><bold>0.026</bold>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Ranging on land and river</td>
<td align="left" rowspan="1" colspan="1">8 (66.7)</td>
<td align="left" rowspan="1" colspan="1">585 (33.8)</td>
<td align="left" rowspan="1" colspan="1"><bold>3.91 (1.17–13.04)</bold>
</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Type of ducks</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Broiler ducks</td>
<td align="left" rowspan="1" colspan="1">3 (25.0)</td>
<td align="left" rowspan="1" colspan="1">1175 (68.0)</td>
<td align="left" rowspan="1" colspan="1"><bold>Reference</bold>
</td>
<td align="left" rowspan="1" colspan="1"><bold>0.006</bold>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Layer ducks</td>
<td align="left" rowspan="1" colspan="1">9 (75.0)</td>
<td align="left" rowspan="1" colspan="1">554 (32.0)</td>
<td align="left" rowspan="1" colspan="1"><bold>6.36 (1.72–23.59)</bold>
</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Avian influenza vaccination in ducks</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">11 (91.7)</td>
<td align="left" rowspan="1" colspan="1">1314 (76.0)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">1 (8.3)</td>
<td align="left" rowspan="1" colspan="1">415 (24.0)</td>
<td align="left" rowspan="1" colspan="1">0.29 (0.04–2.24)</td>
<td align="left" rowspan="1" colspan="1">0.234</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Ducks in contact with other birds</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">5 (41.7)</td>
<td align="left" rowspan="1" colspan="1">1274 (73.7)</td>
<td align="left" rowspan="1" colspan="1"><bold>Reference</bold>
</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">7 (58.3)</td>
<td align="left" rowspan="1" colspan="1">455 (26.3)</td>
<td align="left" rowspan="1" colspan="1"><bold>3.92 (1.24–12.41)</bold>
</td>
<td align="left" rowspan="1" colspan="1"><bold>0.020</bold>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Frequency of disinfection of worksite</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">>twice monthly</td>
<td align="left" rowspan="1" colspan="1">2 (16.7)</td>
<td align="left" rowspan="1" colspan="1">1036 (59.9)</td>
<td align="left" rowspan="1" colspan="1"><bold>Reference</bold>
</td>
<td align="left" rowspan="1" colspan="1"><bold>0.010</bold>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">≤ twice monthly</td>
<td align="left" rowspan="1" colspan="1">10 (83.3)</td>
<td align="left" rowspan="1" colspan="1">693 (40.1)</td>
<td align="left" rowspan="1" colspan="1"><bold>7.48 (1.63–34.22)</bold>
</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Mask use</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">1 (8.3)</td>
<td align="left" rowspan="1" colspan="1">731 (42.3)</td>
<td align="left" rowspan="1" colspan="1"><bold>Reference</bold>
</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">11 (91.7)</td>
<td align="left" rowspan="1" colspan="1">998 (57.7)</td>
<td align="left" rowspan="1" colspan="1"><bold>8.06 (1.04–62.55)</bold>
</td>
<td align="left" rowspan="1" colspan="1"><bold>0.046</bold>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Glove use</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">3 (25.0)</td>
<td align="left" rowspan="1" colspan="1">815 (47.1)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">9 (75.0)</td>
<td align="left" rowspan="1" colspan="1">914 (52.9)</td>
<td align="left" rowspan="1" colspan="1">2.68 (0.72–9.92)</td>
<td align="left" rowspan="1" colspan="1">0.141</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Handling ducks with wounds on hands</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">5 (41.7)</td>
<td align="left" rowspan="1" colspan="1">1416 (81.9)</td>
<td align="left" rowspan="1" colspan="1"><bold>Reference</bold>
</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">7 (58.3)</td>
<td align="left" rowspan="1" colspan="1">313 (18.1)</td>
<td align="left" rowspan="1" colspan="1"><bold>6.33 (2.00–20.09)</bold>
</td>
<td align="left" rowspan="1" colspan="1"><bold>0.002</bold>
</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Occurrence of sick/dead ducks at worksite</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">10 (83.3)</td>
<td align="left" rowspan="1" colspan="1">1454 (84.1)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">2 (16.7)</td>
<td align="left" rowspan="1" colspan="1">275 (15.9)</td>
<td align="left" rowspan="1" colspan="1">1.06 (0.23–4.85)</td>
<td align="left" rowspan="1" colspan="1">0.943</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Close contact with sick/dead ducks</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">11 (91.7)</td>
<td align="left" rowspan="1" colspan="1">1498 (86.6)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">1 (8.3)</td>
<td align="left" rowspan="1" colspan="1">231 (13.4)</td>
<td align="left" rowspan="1" colspan="1">0.59 (0.08–4.59)</td>
<td align="left" rowspan="1" colspan="1">0.614</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Close contact with other animals</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">9 (75.0)</td>
<td align="left" rowspan="1" colspan="1">917 (53.0)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">3 (25.0)</td>
<td align="left" rowspan="1" colspan="1">812 (47.0)</td>
<td align="left" rowspan="1" colspan="1">0.38 (0.10–1.40)</td>
<td align="left" rowspan="1" colspan="1">0.144</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Exposure to birds outside of work setting<xref ref-type="table-fn" rid="nt106">*</xref>
</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">12 (100)</td>
<td align="left" rowspan="1" colspan="1">1700 (98.3)</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1">1.000</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">0 (0)</td>
<td align="left" rowspan="1" colspan="1">29 (1.7)</td>
<td align="left" rowspan="1" colspan="1">NA</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
</tbody>
</table>
</alternatives>
<table-wrap-foot><fn id="nt105"><label></label>
<p><bold>NOTE.</bold>
Data are frequency (%) of subjects, unless otherwise indicated. Univariate unconditional logistic regression was employed to compare frequencies of exposure between seropositive group and seronegative group. OR, odd ratio; CI, confidence interval; NA, not available. Boldface indicates <italic>P</italic>
<0.1.</p>
</fn>
<fn id="nt106"><label>*</label>
<p>Fisher’s exact test was used because data distribution could not be analyzed by logistic regression.</p>
</fn>
</table-wrap-foot>
</table-wrap>
<p>In multivariate analysis, significant independent risk factors included less frequent disinfection of worksite (OR, 5.13 [95% CI, 1.07–24.58]; <italic>P</italic>
= 0.041; ≤ twice monthly versus>twice monthly) and handling ducks with wounds on hands (OR, 4.13 [95% CI, 1.26–13.57]; <italic>P</italic>
= 0.019) (<xref ref-type="table" rid="pone-0050770-t004">Table 4</xref>
).</p>
<table-wrap id="pone-0050770-t004" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0050770.t004</object-id>
<label>Table 4</label>
<caption><title>Multivariate analysis for risk factors associated with seropositivity for antibodies to H9 virus amongst duck-related workers, Beijing, China.</title>
</caption>
<alternatives><graphic id="pone-0050770-t004-4" xlink:href="pone.0050770.t004"></graphic>
<table frame="hsides" rules="groups"><colgroup span="1"><col align="left" span="1"></col>
<col align="center" span="1"></col>
<col align="center" span="1"></col>
</colgroup>
<thead><tr><td align="left" rowspan="1" colspan="1">Factors</td>
<td align="left" rowspan="1" colspan="1">OR (95% CI)</td>
<td align="left" rowspan="1" colspan="1"><italic>P</italic>
value</td>
</tr>
</thead>
<tbody><tr><td align="left" rowspan="1" colspan="1">Frequency of disinfection of worksite</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">>twice monthly</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">≤ twice monthly</td>
<td align="left" rowspan="1" colspan="1">5.13 (1.07–24.58)</td>
<td align="left" rowspan="1" colspan="1">0.041</td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Handling ducks with wounds on hands</td>
<td align="left" rowspan="1" colspan="1"></td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">No</td>
<td align="left" rowspan="1" colspan="1">Reference</td>
<td align="left" rowspan="1" colspan="1"></td>
</tr>
<tr><td align="left" rowspan="1" colspan="1">Yes</td>
<td align="left" rowspan="1" colspan="1">4.13 (1.26–13.57)</td>
<td align="left" rowspan="1" colspan="1">0.019</td>
</tr>
</tbody>
</table>
</alternatives>
<table-wrap-foot><fn id="nt107"><label></label>
<p><bold>NOTE.</bold>
Those variables with <italic>P</italic>
<0.1 in univariate analysis were included in multivariate unconditional logistic regression analysis. OR, odd ratio; CI, confidence interval.</p>
</fn>
</table-wrap-foot>
</table-wrap>
</sec>
</sec>
<sec id="s4"><title>Discussion</title>
<p>In this study, none of the enrolled workers were seropositive for either H5 or H7 antibodies, but 0.7% had antibody against H9 virus. This finding indicates that the risk of infection with H5, H7 and H9 viruses appears to be low among duck-related workers in Beijing, China, but the risk of infection with H9 virus is slightly elevated in comparison to the other subtypes.</p>
<p>Although HPAI H5N1 virus continues to circulate in chickens and domestic waterfowl in China <xref rid="pone.0050770-Martin1" ref-type="bibr">[27]</xref>
, human infection with HPAI H5N1 virus so far has been rare, with only 43 human cases as of the end of September, 2012 <xref rid="pone.0050770-World1" ref-type="bibr">[16]</xref>
. Low rates of subclinical infection in poultry (chickens of domestic waterfowl) workers have previously been documented in a number of Chinese studies <xref rid="pone.0050770-Huo1" ref-type="bibr">[28]</xref>
, <xref rid="pone.0050770-Wang1" ref-type="bibr">[29]</xref>
. In addition, studies conducted in other countries have also reported low frequency of transmission of this virus to poultry (chickens of domestic waterfowl) workers <xref rid="pone.0050770-Schultsz1" ref-type="bibr">[30]</xref>
–<xref rid="pone.0050770-Vong2" ref-type="bibr">[32]</xref>
. These reports and our findings indicate that there continues to be a strong host specificity of infection with the H5 virus.</p>
<p>In agreement with a previous study from Northern China, we did not find any subjects who were seropositive to the H7 virus <xref rid="pone.0050770-Jia1" ref-type="bibr">[33]</xref>
. In comparison, previous European studies have documented higher frequencies of human infection with the H7 viruses <xref rid="pone.0050770-Kurtz1" ref-type="bibr">[3]</xref>
–<xref rid="pone.0050770-Editorial1" ref-type="bibr">[6]</xref>
. This correlates well to the surveillance studies of H7 viruses in birds which have documented persistent epidemics of the virus in birds in many European countries <xref rid="pone.0050770-Alexander1" ref-type="bibr">[1]</xref>
, but not in China.</p>
<p>In this study, ten villagers and two farm workers were seropositive to H9 antibody. Previously, a study from Guangzhou in southern China also found that the seroprevalence of antibody against H9 virus (4.5%) in poultry workers was much higher than that against H5 virus (0.2%) <xref rid="pone.0050770-Wang1" ref-type="bibr">[29]</xref>
. In addition, a study conducted in northern China found that 1.5% (12/783) of villagers breeding backyard poultry (chickens or domestic waterfowl) were seropositive to H9 virus, but identified no persons seropositive to H7 virus <xref rid="pone.0050770-Jia1" ref-type="bibr">[33]</xref>
. Our findings, along with those from previous studies support the notion that there is relatively higher risk from H9 virus in China, in comparison to H5 and H7 subtypes.</p>
<p>In the present study, the seroprevalence of antibodies against H9 virus amongst villagers breeding ducks in their backyard was significantly greater than participants from other categories, which was supported by a previous work <xref rid="pone.0050770-Jia1" ref-type="bibr">[33]</xref>
. This difference may be attributed to two reasons as follows: firstly, people raising ducks in their backyards have closer and longer periods of exposure to ducks, and this may put them at increased risk for exposure to viruses; secondly, people who work with ducks in their job are more likely to use personal protective equipment like masks and gloves than people raising ducks in their backyards.</p>
<p>In this study, the seroprevalence of antibodies to H9 virus amongst participants above 50 years was significantly higher than those less than 50 years. As there is no report about the change of susceptibility in human of the H9 viruses that have circulated in China in recent years, we consider that this difference by age may be attributed to a longer period of exposure to ducks in older participants.</p>
<p>Participants who reported that the worksite was infrequently disinfected were more likely to be identified as seropositivity for antibodies to H9 virus in our study. In corroboration are the results from a Korean study that found an increased risk of seropositivity against H9 virus in chickens associated with less frequent cleaning with disinfectants <xref rid="pone.0050770-Woo1" ref-type="bibr">[34]</xref>
. We also found that contact with ducks while having a hand wound was also a risk factor for previous infection with H9 virus amongst the duck workers. Given this finding, glove should be recommended for workers with wounds on hands to use.</p>
<p>It has been reported that handling healthy, sick and dead chickens or domestic waterfowl was the predominant means of human infection with HPAI H5N1, HPAI/LPAI H7 and LPAI H9N2 viruses <xref rid="pone.0050770-AbdelGhafar1" ref-type="bibr">[2]</xref>
–<xref rid="pone.0050770-Guo1" ref-type="bibr">[7]</xref>
. In addition, for patients infected with HPAI H5N1, contact with virus-contaminated fomites followed by self-inoculation of the respiratory tract or inhalation of aerosolized infectious excreta was also plausible transmission route <xref rid="pone.0050770-AbdelGhafar1" ref-type="bibr">[2]</xref>
. Therefore, mask or glove use may theoretically provide protection against H5, H7 and H9 viruses for persons having frequent contact with chickens or domestic waterfowl. In the present study, no mask use was a significant risk factor for previous infection with H9 virus in univariate analysis, but not in multivariate analysis; no glove use was not a significant risk factor either in univariate analysis or in multivariate analysis. Due to the small number of persons seropositive to H5, H7 and H9 viruses, this study may be underpowered to assess the effect of mask or glove use.</p>
<p>The LPAI H9N2 virus strain used in our HI assay, belonging to the BJ94-like lineage, was isolated in 1999, and it was the diagnostic antigen for detecting antibodies to H9 virus recommended by the agricultural authorities in China. Although H9N2 viruses circulating in China had experienced genetic and antigenic changes since 1999, it was found that similar sequence and obvious cross-reactivity in HI assay existed between H9N2 viruses isolated around 1999 and those isolated in the recent years, and all these viruses still belonged to BJ94-like lineage <xref rid="pone.0050770-Ji1" ref-type="bibr">[35]</xref>
, <xref rid="pone.0050770-Zhang1" ref-type="bibr">[36]</xref>
. In addition, as most of patients infected with LPAI H9N2 virus in China were also found around 1999 <xref rid="pone.0050770-Guo1" ref-type="bibr">[7]</xref>
–<xref rid="pone.0050770-Butt1" ref-type="bibr">[10]</xref>
, using the virus isolated at that time for HI assay may have higher efficiency to detect human infection with H9 virus crossing the species barrier. In addition, although Beijing and Shanghai are located in different regions of China, there were no distinct regional differences found in LPAI H9N2 viruses circulating in China previously <xref rid="pone.0050770-Ji1" ref-type="bibr">[35]</xref>
, <xref rid="pone.0050770-Zhang1" ref-type="bibr">[36]</xref>
. Based on the above-mentioned reasons, we selected A/Chicken/Shanghai/10/1999 (LPAI H9N2) strain used in the HI assay for our study.</p>
<p>In this study, we applied HI assay using horse erythrocytes to detect human sera for antibodies to H5, H7 and H9 viruses. HI assay using horse erythrocytes has high sensitivity and specificity in detecting human antibodies against avian-specific influenza viruses <xref rid="pone.0050770-Kayali1" ref-type="bibr">[24]</xref>
, <xref rid="pone.0050770-Meijer1" ref-type="bibr">[26]</xref>
. In comparison with HI assay using chicken or turkey erythrocytes, HI assay using horse erythrocytes has increased sensitivity, which may be explained by the fact that horse erythrocytes express a higher proportion of sialic acid containing N-acetylneuraminic acid α2,3-galactose (SAα2,3Gal) linkages which avian-specific influenza viruses preferentially bind <xref rid="pone.0050770-Jia2" ref-type="bibr">[37]</xref>
–<xref rid="pone.0050770-Stephenson1" ref-type="bibr">[39]</xref>
.</p>
<p>The study population in this study was the people related to domestic ducks. However, in fact the people frequently exposed to wild ducks should be concerned about as well because wild birds are thought to form the reservoir of influenza A viruses in nature <xref rid="pone.0050770-Olsen1" ref-type="bibr">[40]</xref>
. It was ever reported by Gill <italic>et al</italic>
that of 39 duck hunters and 68 wildlife professionals in the US, three had previous infection with H11N9 virus <xref rid="pone.0050770-Gill1" ref-type="bibr">[41]</xref>
. In addition, as the worksites of the participants in our study were mainly located in rural areas, they also had the opportunity to contact wild birds and be exposed to wild bird-origin virus strains. The antigens used in this study are the diagnostic antigens recommended by agricultural authorities in China for testing antibodies against viruses in poultry (chickens or domestic waterfowl), thus we are not sure if these antigens could be used for detecting antibodies elicited by wild bird-origin strains. However, considering the similarity between wild bird-origin strains and poultry-origin strains <xref rid="pone.0050770-Li1" ref-type="bibr">[42]</xref>
–<xref rid="pone.0050770-Kou1" ref-type="bibr">[44]</xref>
, we think antigenic cross-reactivity in HI assay may exist between antigens used in this study and wild bird-origin strains.</p>
<p>This study has several limitations. Firstly, information regarding the exposures of participants to ducks was all based on self-report, and this study is therefore subject to recall bias. Sencondly, we only detected twelve subjects with antibody against H9 virus; therefore, this study was probably underpowered as the result of the small sample size to detect other potentially significant risk factors for previous infection. Thirdly, there could be some risk factors that were not taken into account in this study. It was a limitation that we could not assess the effect of visiting live poultry markets because selling live poultry in food markets had been banned in Beijing since 2005.</p>
<p>In summary, the risk of infection with H5, H7 and H9 viruses appears to be low among duck-related workers in Beijing, China, but closer monitoring of infection with the H9 virus should be warranted, especially amongst villagers breeding ducks in their backyards. Less frequent disinfection of the worksites and having contact with ducks while having hand wounds were both independent risk factors for previous infection with H9 virus amongst the duck workers.</p>
</sec>
</body>
<back><ack><p>We thank District Centers for Disease Prevention and Control in Beijing for assisting us in field investigation.</p>
</ack>
<ref-list><title>References</title>
<ref id="pone.0050770-Alexander1"><label>1</label>
<mixed-citation publication-type="journal"><name><surname>Alexander</surname>
<given-names>DJ</given-names>
</name>
(<year>2007</year>
) <article-title>Summary of avian influenza activity in Europe, Asia, Africa, and Australasia, 2002–2006</article-title>
. <source>Avian Dis</source>
<volume>51</volume>
: <fpage>161</fpage>
–<lpage>166</lpage>
.<pub-id pub-id-type="pmid">17494548</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-AbdelGhafar1"><label>2</label>
<mixed-citation publication-type="journal"><name><surname>Abdel-Ghafar</surname>
<given-names>AN</given-names>
</name>
, <name><surname>Chotpitayasunondh</surname>
<given-names>T</given-names>
</name>
, <name><surname>Gao</surname>
<given-names>Z</given-names>
</name>
, <name><surname>Hayden</surname>
<given-names>FG</given-names>
</name>
, <name><surname>Nguyen</surname>
<given-names>DH</given-names>
</name>
, <etal>et al</etal>
(<year>2008</year>
) <article-title>Update on avian influenza A (H5N1) virus infection in humans</article-title>
. <source>N Engl J Med</source>
<volume>358</volume>
: <fpage>261</fpage>
–<lpage>273</lpage>
.<pub-id pub-id-type="pmid">18199865</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Kurtz1"><label>3</label>
<mixed-citation publication-type="journal"><name><surname>Kurtz</surname>
<given-names>J</given-names>
</name>
, <name><surname>Manvell</surname>
<given-names>RJ</given-names>
</name>
, <name><surname>Banks</surname>
<given-names>J</given-names>
</name>
(<year>1996</year>
) <article-title>Avian influenza virus isolated from a woman with conjunctivitis</article-title>
. <source>Lancet</source>
<volume>348</volume>
: <fpage>901</fpage>
–<lpage>902</lpage>
.<pub-id pub-id-type="pmid">8826845</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Koopmans1"><label>4</label>
<mixed-citation publication-type="journal"><name><surname>Koopmans</surname>
<given-names>M</given-names>
</name>
, <name><surname>Wilbrink</surname>
<given-names>B</given-names>
</name>
, <name><surname>Conyn</surname>
<given-names>M</given-names>
</name>
, <name><surname>Natrop</surname>
<given-names>G</given-names>
</name>
, <name><surname>van der Nat</surname>
<given-names>H</given-names>
</name>
, <etal>et al</etal>
(<year>2004</year>
) <article-title>Transmission of H7N7 avian influenza A virus to human beings during a large outbreak in commercial poultry farms in the Netherlands</article-title>
. <source>Lancet</source>
<volume>363</volume>
: <fpage>587</fpage>
–<lpage>593</lpage>
.<pub-id pub-id-type="pmid">14987882</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Fouchier1"><label>5</label>
<mixed-citation publication-type="journal"><name><surname>Fouchier</surname>
<given-names>RA</given-names>
</name>
, <name><surname>Schneeberger</surname>
<given-names>PM</given-names>
</name>
, <name><surname>Rozendaal</surname>
<given-names>FW</given-names>
</name>
, <name><surname>Broekman</surname>
<given-names>JM</given-names>
</name>
, <name><surname>Kemink</surname>
<given-names>SA</given-names>
</name>
, <etal>et al</etal>
(<year>2004</year>
) <article-title>Avian influenza A virus (H7N7) associated with human conjunctivitis and a fatal case of acute respiratory distress syndrome</article-title>
. <source>Proc Natl Acad Sci U S A</source>
<volume>101</volume>
: <fpage>1356</fpage>
–<lpage>1361</lpage>
.<pub-id pub-id-type="pmid">14745020</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Editorial1"><label>6</label>
<mixed-citation publication-type="journal"><collab>Editorial team</collab>
(<year>2007</year>
) <article-title>Avian influenza A/(H7N2) outbreak in the United Kingdom</article-title>
. <source>Euro Surveill</source>
<volume>12</volume>
: <fpage>3206</fpage>
.</mixed-citation>
</ref>
<ref id="pone.0050770-Guo1"><label>7</label>
<mixed-citation publication-type="journal"><name><surname>Guo</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Li</surname>
<given-names>J</given-names>
</name>
, <name><surname>Cheng</surname>
<given-names>X</given-names>
</name>
(<year>1999</year>
) <article-title>Discovery of men infected by avian influenza A (H9N2) virus</article-title>
. <source>Zhonghua Shi Yan He Lin Chuang Bing Du Xue Za Zhi</source>
<volume>13</volume>
: <fpage>105</fpage>
–<lpage>108</lpage>
.<pub-id pub-id-type="pmid">12569771</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Guo2"><label>8</label>
<mixed-citation publication-type="journal"><name><surname>Guo</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Xie</surname>
<given-names>J</given-names>
</name>
, <name><surname>Wang</surname>
<given-names>M</given-names>
</name>
(<year>2000</year>
) <article-title>A strain of influenza A H9N2 virus repeatedly isolated from human population in China</article-title>
. <source>Zhonghua Shi Yan He Lin Chuang Bing Du Xue Za Zhi</source>
<volume>14</volume>
: <fpage>209</fpage>
–<lpage>212</lpage>
.<pub-id pub-id-type="pmid">11498680</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Peiris1"><label>9</label>
<mixed-citation publication-type="journal"><name><surname>Peiris</surname>
<given-names>M</given-names>
</name>
, <name><surname>Yuen</surname>
<given-names>KY</given-names>
</name>
, <name><surname>Leung</surname>
<given-names>CW</given-names>
</name>
, <name><surname>Chan</surname>
<given-names>KH</given-names>
</name>
, <name><surname>Ip</surname>
<given-names>PL</given-names>
</name>
, <etal>et al</etal>
(<year>1999</year>
) <article-title>Human infection with influenza H9N2</article-title>
. <source>Lancet</source>
<volume>354</volume>
: <fpage>916</fpage>
–<lpage>917</lpage>
.<pub-id pub-id-type="pmid">10489954</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Butt1"><label>10</label>
<mixed-citation publication-type="journal"><name><surname>Butt</surname>
<given-names>KM</given-names>
</name>
, <name><surname>Smith</surname>
<given-names>GJ</given-names>
</name>
, <name><surname>Chen</surname>
<given-names>H</given-names>
</name>
, <name><surname>Zhang</surname>
<given-names>LJ</given-names>
</name>
, <name><surname>Leung</surname>
<given-names>YH</given-names>
</name>
, <etal>et al</etal>
(<year>2005</year>
) <article-title>Human infection with an avian H9N2 influenza A virus in Hong Kong in 2003</article-title>
. <source>J Clin Microbiol</source>
<volume>43</volume>
: <fpage>5760</fpage>
–<lpage>5767</lpage>
.<pub-id pub-id-type="pmid">16272514</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Lin1"><label>11</label>
<mixed-citation publication-type="journal"><name><surname>Lin</surname>
<given-names>YP</given-names>
</name>
, <name><surname>Shaw</surname>
<given-names>M</given-names>
</name>
, <name><surname>Gregory</surname>
<given-names>V</given-names>
</name>
, <name><surname>Cameron</surname>
<given-names>K</given-names>
</name>
, <name><surname>Lim</surname>
<given-names>W</given-names>
</name>
, <etal>et al</etal>
(<year>2000</year>
) <article-title>Avian-to-human transmission of H9N2 subtype influenza A viruses: relationship between H9N2 and H5N1 human isolates</article-title>
. <source>Proc Natl Acad Sci U S A</source>
<volume>97</volume>
: <fpage>9654</fpage>
–<lpage>9658</lpage>
.<pub-id pub-id-type="pmid">10920197</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Reid1"><label>12</label>
<mixed-citation publication-type="journal"><name><surname>Reid</surname>
<given-names>AH</given-names>
</name>
, <name><surname>Fanning</surname>
<given-names>TG</given-names>
</name>
, <name><surname>Hultin</surname>
<given-names>JV</given-names>
</name>
, <name><surname>Taubenberger</surname>
<given-names>JK</given-names>
</name>
(<year>1999</year>
) <article-title>Origin and evolution of the 1918 “Spanish” influenza virus hemagglutinin gene</article-title>
. <source>Proc Natl Acad Sci U S A</source>
<volume>96</volume>
: <fpage>1651</fpage>
–<lpage>1656</lpage>
.<pub-id pub-id-type="pmid">9990079</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Schafer1"><label>13</label>
<mixed-citation publication-type="journal"><name><surname>Schafer</surname>
<given-names>JR</given-names>
</name>
, <name><surname>Kawaoka</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Bean</surname>
<given-names>WJ</given-names>
</name>
, <name><surname>Suss</surname>
<given-names>J</given-names>
</name>
, <name><surname>Senne</surname>
<given-names>D</given-names>
</name>
, <etal>et al</etal>
(<year>1993</year>
) <article-title>Origin of the pandemic 1957 H2 influenza A virus and the persistence of its possible progenitors in the avian reservoir</article-title>
. <source>Virology</source>
<volume>194</volume>
: <fpage>781</fpage>
–<lpage>788</lpage>
.<pub-id pub-id-type="pmid">7684877</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Scholtissek1"><label>14</label>
<mixed-citation publication-type="journal"><name><surname>Scholtissek</surname>
<given-names>C</given-names>
</name>
, <name><surname>Rohde</surname>
<given-names>W</given-names>
</name>
, <name><surname>Von Hoyningen</surname>
<given-names>V</given-names>
</name>
, <name><surname>Rott</surname>
<given-names>R</given-names>
</name>
(<year>1978</year>
) <article-title>On the origin of the human influenza virus subtypes H2N2 and H3N2</article-title>
. <source>Virology</source>
<volume>87</volume>
: <fpage>13</fpage>
–<lpage>20</lpage>
.<pub-id pub-id-type="pmid">664248</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Dawood1"><label>15</label>
<mixed-citation publication-type="journal"><name><surname>Dawood</surname>
<given-names>FS</given-names>
</name>
, <name><surname>Jain</surname>
<given-names>S</given-names>
</name>
, <name><surname>Finelli</surname>
<given-names>L</given-names>
</name>
, <name><surname>Shaw</surname>
<given-names>MW</given-names>
</name>
, <name><surname>Lindstrom</surname>
<given-names>S</given-names>
</name>
, <etal>et al</etal>
(<year>2009</year>
) <article-title>Emergence of a novel swine-origin influenza A (H1N1) virus in humans</article-title>
. <source>N Engl J Med</source>
<volume>360</volume>
: <fpage>2605</fpage>
–<lpage>2615</lpage>
.<pub-id pub-id-type="pmid">19423869</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-World1"><label>16</label>
<mixed-citation publication-type="other">World Health Organization (2012) Cumulative number of confirmed human cases for avian influenza A(H5N1) reported to WHO, 2003–2012.</mixed-citation>
</ref>
<ref id="pone.0050770-Zhou1"><label>17</label>
<mixed-citation publication-type="journal"><name><surname>Zhou</surname>
<given-names>L</given-names>
</name>
, <name><surname>Liao</surname>
<given-names>Q</given-names>
</name>
, <name><surname>Dong</surname>
<given-names>L</given-names>
</name>
, <name><surname>Huai</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Bai</surname>
<given-names>T</given-names>
</name>
, <etal>et al</etal>
(<year>2009</year>
) <article-title>Risk factors for human illness with avian influenza A (H5N1) virus infection in China</article-title>
. <source>J Infect Dis</source>
<volume>199</volume>
: <fpage>1726</fpage>
–<lpage>1734</lpage>
.<pub-id pub-id-type="pmid">19416076</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Cavailler1"><label>18</label>
<mixed-citation publication-type="journal"><name><surname>Cavailler</surname>
<given-names>P</given-names>
</name>
, <name><surname>Chu</surname>
<given-names>S</given-names>
</name>
, <name><surname>Ly</surname>
<given-names>S</given-names>
</name>
, <name><surname>Garcia</surname>
<given-names>JM</given-names>
</name>
, <name><surname>Ha do</surname>
<given-names>Q</given-names>
</name>
, <etal>et al</etal>
(<year>2010</year>
) <article-title>Seroprevalence of anti-H5 antibody in rural Cambodia, 2007</article-title>
. <source>J Clin Virol</source>
<volume>48</volume>
: <fpage>123</fpage>
–<lpage>126</lpage>
.<pub-id pub-id-type="pmid">20356781</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-VanKerkhove1"><label>19</label>
<mixed-citation publication-type="journal"><name><surname>Van Kerkhove</surname>
<given-names>MD</given-names>
</name>
, <name><surname>Ly</surname>
<given-names>S</given-names>
</name>
, <name><surname>Holl</surname>
<given-names>D</given-names>
</name>
, <name><surname>Guitian</surname>
<given-names>J</given-names>
</name>
, <name><surname>Mangtani</surname>
<given-names>P</given-names>
</name>
, <etal>et al</etal>
(<year>2008</year>
) <article-title>Frequency and patterns of contact with domestic poultry and potential risk of H5N1 transmission to humans living in rural Cambodia</article-title>
. <source>Influenza Other Respi Viruses</source>
<volume>2</volume>
: <fpage>155</fpage>
–<lpage>163</lpage>
.</mixed-citation>
</ref>
<ref id="pone.0050770-Dinh1"><label>20</label>
<mixed-citation publication-type="journal"><name><surname>Dinh</surname>
<given-names>PN</given-names>
</name>
, <name><surname>Long</surname>
<given-names>HT</given-names>
</name>
, <name><surname>Tien</surname>
<given-names>NT</given-names>
</name>
, <name><surname>Hien</surname>
<given-names>NT</given-names>
</name>
, <name><surname>Mai le</surname>
<given-names>TQ</given-names>
</name>
, <etal>et al</etal>
(<year>2006</year>
) <article-title>Risk factors for human infection with avian influenza A H5N1, Vietnam, 2004</article-title>
. <source>Emerg Infect Dis</source>
<volume>12</volume>
: <fpage>1841</fpage>
–<lpage>1847</lpage>
.<pub-id pub-id-type="pmid">17326934</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Vong1"><label>21</label>
<mixed-citation publication-type="journal"><name><surname>Vong</surname>
<given-names>S</given-names>
</name>
, <name><surname>Ly</surname>
<given-names>S</given-names>
</name>
, <name><surname>Van Kerkhove</surname>
<given-names>MD</given-names>
</name>
, <name><surname>Achenbach</surname>
<given-names>J</given-names>
</name>
, <name><surname>Holl</surname>
<given-names>D</given-names>
</name>
, <etal>et al</etal>
(<year>2009</year>
) <article-title>Risk factors associated with subclinical human infection with avian influenza A (H5N1) virus–Cambodia, 2006</article-title>
. <source>J Infect Dis</source>
<volume>199</volume>
: <fpage>1744</fpage>
–<lpage>1752</lpage>
.<pub-id pub-id-type="pmid">19416078</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Mounts1"><label>22</label>
<mixed-citation publication-type="journal"><name><surname>Mounts</surname>
<given-names>AW</given-names>
</name>
, <name><surname>Kwong</surname>
<given-names>H</given-names>
</name>
, <name><surname>Izurieta</surname>
<given-names>HS</given-names>
</name>
, <name><surname>Ho</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Au</surname>
<given-names>T</given-names>
</name>
, <etal>et al</etal>
(<year>1999</year>
) <article-title>Case-control study of risk factors for avian influenza A (H5N1) disease, Hong Kong, 1997</article-title>
. <source>J Infect Dis</source>
<volume>180</volume>
: <fpage>505</fpage>
–<lpage>508</lpage>
.<pub-id pub-id-type="pmid">10395870</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Shortridge1"><label>23</label>
<mixed-citation publication-type="journal"><name><surname>Shortridge</surname>
<given-names>KF</given-names>
</name>
, <name><surname>Stuart-Harris</surname>
<given-names>CH</given-names>
</name>
(<year>1982</year>
) <article-title>An influenza epicentre?</article-title>
<source>Lancet</source>
<volume>2</volume>
: <fpage>812</fpage>
–<lpage>813</lpage>
.<pub-id pub-id-type="pmid">6126676</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Kayali1"><label>24</label>
<mixed-citation publication-type="journal"><name><surname>Kayali</surname>
<given-names>G</given-names>
</name>
, <name><surname>Setterquist</surname>
<given-names>SF</given-names>
</name>
, <name><surname>Capuano</surname>
<given-names>AW</given-names>
</name>
, <name><surname>Myers</surname>
<given-names>KP</given-names>
</name>
, <name><surname>Gill</surname>
<given-names>JS</given-names>
</name>
, <etal>et al</etal>
(<year>2008</year>
) <article-title>Testing human sera for antibodies against avian influenza viruses: horse RBC hemagglutination inhibition vs. microneutralization assays</article-title>
. <source>J Clin Virol</source>
<volume>43</volume>
: <fpage>73</fpage>
–<lpage>78</lpage>
.<pub-id pub-id-type="pmid">18571465</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Pawar1"><label>25</label>
<mixed-citation publication-type="journal"><name><surname>Pawar</surname>
<given-names>SD</given-names>
</name>
, <name><surname>Tandale</surname>
<given-names>BV</given-names>
</name>
, <name><surname>Raut</surname>
<given-names>CG</given-names>
</name>
, <name><surname>Parkhi</surname>
<given-names>SS</given-names>
</name>
, <name><surname>Barde</surname>
<given-names>TD</given-names>
</name>
, <etal>et al</etal>
(<year>2012</year>
) <article-title>Avian influenza H9N2 seroprevalence among poultry workers in Pune, India, 2010</article-title>
. <source>PLoS One</source>
<volume>7</volume>
: <fpage>e36374</fpage>
.<pub-id pub-id-type="pmid">22623954</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Meijer1"><label>26</label>
<mixed-citation publication-type="journal"><name><surname>Meijer</surname>
<given-names>A</given-names>
</name>
, <name><surname>Bosman</surname>
<given-names>A</given-names>
</name>
, <name><surname>van de Kamp</surname>
<given-names>EE</given-names>
</name>
, <name><surname>Wilbrink</surname>
<given-names>B</given-names>
</name>
, <name><surname>Du Ry van Beest Holle</surname>
<given-names>M</given-names>
</name>
, <etal>et al</etal>
(<year>2006</year>
) <article-title>Measurement of antibodies to avian influenza virus A(H7N7) in humans by hemagglutination inhibition test</article-title>
. <source>J Virol Methods</source>
<volume>132</volume>
: <fpage>113</fpage>
–<lpage>120</lpage>
.<pub-id pub-id-type="pmid">16271401</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Martin1"><label>27</label>
<mixed-citation publication-type="journal"><name><surname>Martin</surname>
<given-names>V</given-names>
</name>
, <name><surname>Pfeiffer</surname>
<given-names>DU</given-names>
</name>
, <name><surname>Zhou</surname>
<given-names>X</given-names>
</name>
, <name><surname>Xiao</surname>
<given-names>X</given-names>
</name>
, <name><surname>Prosser</surname>
<given-names>DJ</given-names>
</name>
, <etal>et al</etal>
(<year>2011</year>
) <article-title>Spatial distribution and risk factors of highly pathogenic avian influenza (HPAI) H5N1 in China</article-title>
. <source>PLoS Pathog</source>
<volume>7</volume>
: <fpage>e1001308</fpage>
.<pub-id pub-id-type="pmid">21408202</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Huo1"><label>28</label>
<mixed-citation publication-type="journal"><name><surname>Huo</surname>
<given-names>X</given-names>
</name>
, <name><surname>Zu</surname>
<given-names>R</given-names>
</name>
, <name><surname>Qi</surname>
<given-names>X</given-names>
</name>
, <name><surname>Qin</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Li</surname>
<given-names>L</given-names>
</name>
, <etal>et al</etal>
(<year>2012</year>
) <article-title>Seroprevalence of avian influenza A (H5N1) virus among poultry workers in Jiangsu Province, China: an observational study</article-title>
. <source>BMC Infect Dis</source>
<volume>12</volume>
: <fpage>93</fpage>
.<pub-id pub-id-type="pmid">22512873</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Wang1"><label>29</label>
<mixed-citation publication-type="journal"><name><surname>Wang</surname>
<given-names>M</given-names>
</name>
, <name><surname>Fu</surname>
<given-names>CX</given-names>
</name>
, <name><surname>Zheng</surname>
<given-names>BJ</given-names>
</name>
(<year>2009</year>
) <article-title>Antibodies against H5 and H9 avian influenza among poultry workers in China</article-title>
. <source>N Engl J Med</source>
<volume>360</volume>
: <fpage>2583</fpage>
–<lpage>2584</lpage>
.<pub-id pub-id-type="pmid">19516044</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Schultsz1"><label>30</label>
<mixed-citation publication-type="journal"><name><surname>Schultsz</surname>
<given-names>C</given-names>
</name>
, <name><surname>Nguyen</surname>
<given-names>VD</given-names>
</name>
, <name><surname>Hai le</surname>
<given-names>T</given-names>
</name>
, <name><surname>Do</surname>
<given-names>QH</given-names>
</name>
, <name><surname>Peiris</surname>
<given-names>JS</given-names>
</name>
, <etal>et al</etal>
(<year>2009</year>
) <article-title>Prevalence of antibodies against avian influenza A (H5N1) virus among Cullers and poultry workers in Ho Chi Minh City, 2005</article-title>
. <source>PLoS ONE</source>
<volume>4</volume>
: <fpage>e7948</fpage>
.<pub-id pub-id-type="pmid">19956765</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Hinjoy1"><label>31</label>
<mixed-citation publication-type="journal"><name><surname>Hinjoy</surname>
<given-names>S</given-names>
</name>
, <name><surname>Puthavathana</surname>
<given-names>P</given-names>
</name>
, <name><surname>Laosiritaworn</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Limpakarnjanarat</surname>
<given-names>K</given-names>
</name>
, <name><surname>Pooruk</surname>
<given-names>P</given-names>
</name>
, <etal>et al</etal>
(<year>2008</year>
) <article-title>Low frequency of infection with avian influenza virus (H5N1) among poultry farmers, Thailand, 2004</article-title>
. <source>Emerg Infect Dis</source>
<volume>14</volume>
: <fpage>499</fpage>
–<lpage>501</lpage>
.<pub-id pub-id-type="pmid">18325273</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Vong2"><label>32</label>
<mixed-citation publication-type="journal"><name><surname>Vong</surname>
<given-names>S</given-names>
</name>
, <name><surname>Coghlan</surname>
<given-names>B</given-names>
</name>
, <name><surname>Mardy</surname>
<given-names>S</given-names>
</name>
, <name><surname>Holl</surname>
<given-names>D</given-names>
</name>
, <name><surname>Seng</surname>
<given-names>H</given-names>
</name>
, <etal>et al</etal>
(<year>2006</year>
) <article-title>Low frequency of poultry-to-human H5NI virus transmission, southern Cambodia, 2005</article-title>
. <source>Emerg Infect Dis</source>
<volume>12</volume>
: <fpage>1542</fpage>
–<lpage>1547</lpage>
.<pub-id pub-id-type="pmid">17176569</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Jia1"><label>33</label>
<mixed-citation publication-type="journal"><name><surname>Jia</surname>
<given-names>N</given-names>
</name>
, <name><surname>de Vlas</surname>
<given-names>SJ</given-names>
</name>
, <name><surname>Liu</surname>
<given-names>YX</given-names>
</name>
, <name><surname>Zhang</surname>
<given-names>JS</given-names>
</name>
, <name><surname>Zhan</surname>
<given-names>L</given-names>
</name>
, <etal>et al</etal>
(<year>2009</year>
) <article-title>Serological reports of human infections of H7 and H9 avian influenza viruses in northern China</article-title>
. <source>J Clin Virol</source>
<volume>44</volume>
: <fpage>225</fpage>
–<lpage>229</lpage>
.<pub-id pub-id-type="pmid">19186101</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Woo1"><label>34</label>
<mixed-citation publication-type="journal"><name><surname>Woo</surname>
<given-names>JT</given-names>
</name>
, <name><surname>Park</surname>
<given-names>BK</given-names>
</name>
(<year>2008</year>
) <article-title>Seroprevalence of low pathogenic avian influenza (H9N2) and associated risk factors in the Gyeonggi-do of Korea during 2005–2006</article-title>
. <source>J Vet Sci</source>
<volume>9</volume>
: <fpage>161</fpage>
–<lpage>168</lpage>
.<pub-id pub-id-type="pmid">18487937</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Ji1"><label>35</label>
<mixed-citation publication-type="journal"><name><surname>Ji</surname>
<given-names>K</given-names>
</name>
, <name><surname>Jiang</surname>
<given-names>WM</given-names>
</name>
, <name><surname>Liu</surname>
<given-names>S</given-names>
</name>
, <name><surname>Chen</surname>
<given-names>JM</given-names>
</name>
, <name><surname>Chen</surname>
<given-names>J</given-names>
</name>
, <etal>et al</etal>
(<year>2010</year>
) <article-title>Characterization of the hemagglutinin gene of subtype H9 avian influenza viruses isolated in 2007–2009 in China</article-title>
. <source>J Virol Methods</source>
<volume>163</volume>
: <fpage>186</fpage>
–<lpage>189</lpage>
.<pub-id pub-id-type="pmid">19781574</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Zhang1"><label>36</label>
<mixed-citation publication-type="journal"><name><surname>Zhang</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Yin</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Bi</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Wang</surname>
<given-names>S</given-names>
</name>
, <name><surname>Xu</surname>
<given-names>S</given-names>
</name>
, <etal>et al</etal>
(<year>2012</year>
) <article-title>Molecular and antigenic characterization of H9N2 avian influenza virus isolates from chicken flocks between 1998 and 2007 in China</article-title>
. <source>Vet Microbiol</source>
<volume>156</volume>
: <fpage>285</fpage>
–<lpage>293</lpage>
.<pub-id pub-id-type="pmid">22177969</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Jia2"><label>37</label>
<mixed-citation publication-type="journal"><name><surname>Jia</surname>
<given-names>N</given-names>
</name>
, <name><surname>Wang</surname>
<given-names>SX</given-names>
</name>
, <name><surname>Liu</surname>
<given-names>YX</given-names>
</name>
, <name><surname>Zhang</surname>
<given-names>PH</given-names>
</name>
, <name><surname>Zuo</surname>
<given-names>SQ</given-names>
</name>
, <etal>et al</etal>
(<year>2008</year>
) <article-title>Increased sensitivity for detecting avian influenza-specific antibodies by a modified hemagglutination inhibition assay using horse erythrocytes</article-title>
. <source>J Virol Methods</source>
<volume>153</volume>
: <fpage>43</fpage>
–<lpage>48</lpage>
.<pub-id pub-id-type="pmid">18634828</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Ito1"><label>38</label>
<mixed-citation publication-type="journal"><name><surname>Ito</surname>
<given-names>T</given-names>
</name>
, <name><surname>Suzuki</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Mitnaul</surname>
<given-names>L</given-names>
</name>
, <name><surname>Vines</surname>
<given-names>A</given-names>
</name>
, <name><surname>Kida</surname>
<given-names>H</given-names>
</name>
, <etal>et al</etal>
(<year>1997</year>
) <article-title>Receptor specificity of influenza A viruses correlates with the agglutination of erythrocytes from different animal species</article-title>
. <source>Virology</source>
<volume>227</volume>
: <fpage>493</fpage>
–<lpage>499</lpage>
.<pub-id pub-id-type="pmid">9018149</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Stephenson1"><label>39</label>
<mixed-citation publication-type="journal"><name><surname>Stephenson</surname>
<given-names>I</given-names>
</name>
, <name><surname>Wood</surname>
<given-names>JM</given-names>
</name>
, <name><surname>Nicholson</surname>
<given-names>KG</given-names>
</name>
, <name><surname>Zambon</surname>
<given-names>MC</given-names>
</name>
(<year>2003</year>
) <article-title>Sialic acid receptor specificity on erythrocytes affects detection of antibody to avian influenza haemagglutinin</article-title>
. <source>J Med Virol</source>
<volume>70</volume>
: <fpage>391</fpage>
–<lpage>398</lpage>
.<pub-id pub-id-type="pmid">12767002</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Olsen1"><label>40</label>
<mixed-citation publication-type="journal"><name><surname>Olsen</surname>
<given-names>B</given-names>
</name>
, <name><surname>Munster</surname>
<given-names>VJ</given-names>
</name>
, <name><surname>Wallensten</surname>
<given-names>A</given-names>
</name>
, <name><surname>Waldenstrom</surname>
<given-names>J</given-names>
</name>
, <name><surname>Osterhaus</surname>
<given-names>AD</given-names>
</name>
, <etal>et al</etal>
(<year>2006</year>
) <article-title>Global patterns of influenza a virus in wild birds</article-title>
. <source>Science</source>
<volume>312</volume>
: <fpage>384</fpage>
–<lpage>388</lpage>
.<pub-id pub-id-type="pmid">16627734</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Gill1"><label>41</label>
<mixed-citation publication-type="journal"><name><surname>Gill</surname>
<given-names>JS</given-names>
</name>
, <name><surname>Webby</surname>
<given-names>R</given-names>
</name>
, <name><surname>Gilchrist</surname>
<given-names>MJ</given-names>
</name>
, <name><surname>Gray</surname>
<given-names>GC</given-names>
</name>
(<year>2006</year>
) <article-title>Avian influenza among waterfowl hunters and wildlife professionals</article-title>
. <source>Emerg Infect Dis</source>
<volume>12</volume>
: <fpage>1284</fpage>
–<lpage>1286</lpage>
.<pub-id pub-id-type="pmid">16965717</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Li1"><label>42</label>
<mixed-citation publication-type="journal"><name><surname>Li</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Shi</surname>
<given-names>J</given-names>
</name>
, <name><surname>Zhong</surname>
<given-names>G</given-names>
</name>
, <name><surname>Deng</surname>
<given-names>G</given-names>
</name>
, <name><surname>Tian</surname>
<given-names>G</given-names>
</name>
, <etal>et al</etal>
(<year>2010</year>
) <article-title>Continued evolution of H5N1 influenza viruses in wild birds, domestic poultry, and humans in China from 2004 to 2009</article-title>
. <source>J Virol</source>
<volume>84</volume>
: <fpage>8389</fpage>
–<lpage>8397</lpage>
.<pub-id pub-id-type="pmid">20538856</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Kim1"><label>43</label>
<mixed-citation publication-type="journal"><name><surname>Kim</surname>
<given-names>HR</given-names>
</name>
, <name><surname>Lee</surname>
<given-names>YJ</given-names>
</name>
, <name><surname>Park</surname>
<given-names>CK</given-names>
</name>
, <name><surname>Oem</surname>
<given-names>JK</given-names>
</name>
, <name><surname>Lee</surname>
<given-names>OS</given-names>
</name>
, <etal>et al</etal>
(<year>2012</year>
) <article-title>Highly pathogenic avian influenza (H5N1) outbreaks in wild birds and poultry, South Korea</article-title>
. <source>Emerg Infect Dis</source>
<volume>18</volume>
: <fpage>480</fpage>
–<lpage>483</lpage>
.<pub-id pub-id-type="pmid">22377052</pub-id>
</mixed-citation>
</ref>
<ref id="pone.0050770-Kou1"><label>44</label>
<mixed-citation publication-type="journal"><name><surname>Kou</surname>
<given-names>Z</given-names>
</name>
, <name><surname>Li</surname>
<given-names>Y</given-names>
</name>
, <name><surname>Yin</surname>
<given-names>Z</given-names>
</name>
, <name><surname>Guo</surname>
<given-names>S</given-names>
</name>
, <name><surname>Wang</surname>
<given-names>M</given-names>
</name>
, <etal>et al</etal>
(<year>2009</year>
) <article-title>The survey of H5N1 flu virus in wild birds in 14 Provinces of China from 2004 to 2007</article-title>
. <source>PLoS ONE</source>
<volume>4</volume>
: <fpage>e6926</fpage>
.<pub-id pub-id-type="pmid">19742325</pub-id>
</mixed-citation>
</ref>
</ref-list>
</back>
</pmc>
</record>
Pour manipuler ce document sous Unix (Dilib)
EXPLOR_STEP=$WICRI_ROOT/Sante/explor/H2N2V1/Data/Pmc/Corpus
HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 000B508 | SxmlIndent | more
Ou
HfdSelect -h $EXPLOR_AREA/Data/Pmc/Corpus/biblio.hfd -nk 000B508 | SxmlIndent | more
Pour mettre un lien sur cette page dans le réseau Wicri
{{Explor lien |wiki= Sante |area= H2N2V1 |flux= Pmc |étape= Corpus |type= RBID |clé= |texte= }}
![]() | This area was generated with Dilib version V0.6.33. | ![]() |