Multiple Introductions of Avian Influenza Viruses (H5N1), Laos, 2009–2010

Stephanie Sonnberg

, Phouvong Phommachanh, Tri Satya Putri Naipospos, Joanna McKenzie, Chintana Chanthavisouk, Som Pathammavong, Daniel Darnell, Phetlamphone Meeduangchanh, Adam M. Rubrum, Mahanakhone Souriya, Bounkhouang Khambounheuang, Richard J. Webby, Bounlom Douangngeun, and Robert G. Webster

Author affiliations: St. Jude Children’s Research Hospital, Memphis, Tennessee, USA (S. Sonnberg, D. Darnell, A.M. Rubrum, R.J. Webby, R.G. Webster); National Animal Health Centre, Vientiane, Laos (P. Phommachanh, P. Meeduangchanh, B. Douangngeun); Food and Agriculture Organization of the United Nations, Rome, Italy (T.S.P. Naipospos, J. McKenzie, C. Chanthavisouk, S. Pathammavong); and; Ministry of Agriculture and Forestry, Vientiane (M. Souriya, B. Khambounheuang)

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.

Since 2003, highly pathogenic avian influenza virus (H5N1) has spread from southern China throughout Southeast Asia and to Europe and Africa (1,2). Since 2003, Laos has experienced outbreaks of clade 1 (2003), clade 2.3.4 (2006, 2007, 2008, 2009, 2010), and clade 2.3.2 viruses (twice in 2008) (3,4). Active surveillance of domestic ducks and chickens in Laos has been limited, but serum antibodies against subtypes H5 and H9 have been detected in ducks. In addition, subtype H5N1 virus was isolated from healthy ducks in 2006, and subtype H3N8 virus was detected in 2007 (4,5). To explore the diversity, extent, and endemicity of avian influenza viruses in Laos, we conducted a survey of healthy domestic poultry throughout the country in March 2010.