Multiple introductions of avian influenza viruses (H5N1), Laos, 2009-2010

Abstract

Avian influenza viruses (H5N1) of clades 2.3.4.1, 2.3.4.2, and 2.3.2.1 were introduced into Laos in 2009-2010. To investigate these viruses, we conducted active surveillance of poultry during March 2010. We detected viruses throughout Laos, including several interclade reassortants and 2 subgroups of clade 2.3.4, one of which caused an outbreak in May 2010.

Figure

Areas sampled and location of subtyped avian influenza viruses (H5N1), Laos, 2009–2010. Provinces that had previous outbreaks of highly pathogenic avian influenza and were part of the survey are indicated in gray, the province that had a previous outbreak but was not part of the survey is indicated in blue, and the province that had not had an outbreak but was part of the survey is indicated in green. Colored dots indicate presence of viruses: light blue, anti-H5 (clade 2.3.4); gray, anti-H9 lineage G1; red, clade 2.3.4.1; orange, clade 2.3.4.2; green, anti-H5 (clade 2.3.2); black, anti-H9 lineage Y280; white, anti-H4; yellow, anti-H6; purple, clade 2.3.2.1 or virus-specific antibodies.

Figure A1

Phylogenetic relationships of hemagglutinin 5 (H5) gene segments of avian influenza viruses (H5N1), Laos, 2009–2010. The tree was rooted in A/goose/Guangdong/1/1996 (nt 91–919, H5 numbering). Surveillance sequences are indicated in boldface and marked with black (isolates) or open (direct sequences) squares. Bootstrap values >75 are shown. Clade numbers are shown on the right. Scale bar indicates nucleotide substitutions per site. A/chicken/Laos/Xayathiani-32/2006-like, A/pigeon/Laos/P0022/2007-like, and A/chicken/Laos/LPQ001/2008-like viruses each represent 3 sequences with identical hemagglutinins. Reference viruses were obtained through EpiFlu of the Global Initiative on Sharing All Influenza Data and provided by the following laboratories in addition to sequences already in the public domain: A/chicken/Vietnam/NCVD-407/2010, A/chicken/Vietnam/NCVD-394/2010, A/chicken/Vietnam/NCVD-398/2010, A/chicken/Vietnam/NCVD-399/2010, A/duck/Vietnam/NCVD-422/2010, A/chicken/NCVD-404/2010, A/Muscovy_duck/Vietnam/NCVD-401/2010, A/chicken/Vietnam/NCVD-421/2010 A/duck/Vietnam/NCVD-423/2010 (original laboratory: National Centre of Veterinary Diagnostics, Hanoi, Vietnam; submitting laboratory: Centers for Disease Control and Prevention, Atlanta, GA, USA); A/Hunan/2/2009, A/Hunan/1/2009, A/Guizhou/1/2009, A/Guangxi/1/2009, A/environment/Guizhou/2/2009, A/environment/Guizhou/4/2009, A/environment/Guizhou/7/2009, A/environment/Guizhou/9/2009, A/water/Hunan/7/2009A/Guangxi/1/2008, A/Guangdong/1/2008, A/Hunan/1/2008, A/duck feces/Hebei/5/2009 (original and submitting laboratory: World Health Organization Chinese National Influenza Center, Beijing, China), Jiangsu/1-like–A/tree_sparrow/Jiangsu/1/2008–like viruses.