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A large-scale cross-sectional seroprevalence study of dengue (DEN) and Japanese encephalitis (JE) was conducted in Khammouane province, Lao PDR, as part of the initial baseline health impact assessment of the Nam Theun 2 hydroelectric dam construction project. Health surveys were performed between May 2007 and February 2008 with serum samples collected from healthy individuals involved in the resettlement program of 16 villages (total surveyed population 4,369). Hemagglutination inhibition assay using flavivirus antigens (DENV1, DENV3, and JEV) performed on 1,708 plasma specimens revealed 30.4% (519) cross-reactive positives, and 10% (172) and 1.3% (22) positives to JEV or DENV, respectively. Entomological surveys conducted during the rainy season of 2008 indicated the presence of competent flavivirus vectors (Culex vishnui group and Aedes albopictus), although Aedes aegypti was not found. Continued surveillance and investigation is warranted to assess the clinical disease burden of flaviviruses in this area that is undergoing rapid ecological and demographic change.
Financial support: Contributions of J. E. Bryant were supported by Agence française de développement (AFD), SISEA/Pasteur Project. This project was supported by the Fondation EDF Diversiterre.
Authors' addresses: Alexandra Hiscox, London School of Hygiene and Tropical Medicine, London, UK and Institut Pasteur du Laos, Lao PDR, E-mail: alexandra.hiscox@lshtm.ac.uk. Christian H. Winter, E-mail: henrik-winter@gmx.de. Phengta Vongphrachanh, Thongchanh Sisouk, and Virasack Somoulay, National Center for Laboratory and Epidemiology, Ministry of Health, Vientiane, Lao PDR, E-mails: phengta@hotmail.com, ssk_thong@yahoo.com, and virasacksom@hotmail.com. Samlane Phompida, Center for Malaria, Parasitology, and Entomology, Lao PDR, E-mail: p.samlane@gmail.com. Surinder Kaul and Pany Sananikhom, Nam Theun 2 Power Company, Vientiane, Lao PDR, E-mails: surinder@namtheun2.com and pany@namtheun2.com. Nguyen Thi Yen, National Institute of Hygiene and Epidemiology, Hanoi, Vietnam, E-mail: yenanihe@yahoo.com. Richard E. Paul, Institut Pasteur, Paris, France, E-mail: rpaul@pasteur.fr. Paul Brey, Institut Pasteur du Laos, Lao PDR, E-mail: pbrey@pasteur.fr. Juliet E. Bryant: National Center for Laboratory and Epidemiology, Ministry of Health, Vientiane, Lao PDR and Institut Pasteur, Paris, France, E-mail: jbryant@oucru.org.