Pandemic (H1N1) 2009 Virus on Swine Farm, Thailand, Table 1 | CDC EID

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Volume 16, Number 10–October 2010
Dispatch
Pandemic (H1N1) 2009 Virus on Commercial Swine Farm, Thailand
Donruethai Sreta, Siriporn Tantawet, Suparlark N. Na Ayudhya, Aunyaratana Thontiravong, Manoosak Wongphatcharachai, Jiradej Lapkuntod, Napawan Bunpapong, Ranida Tuanudom, Sanipa Suradhat, Linda Vimolket, Yong Poovorawan, Roongroje Thanawongnuwech, Alongkorn Amonsin, and Pravina Kitikoon
Author affiliations: Chulalongkorn University, Bangkok, Thailand (D. Sreta, S.N. Na Ayudhya, A. Thontiravong, M. Wongphatcharachai, J. Lapkuntod, N. Bunpapong, R. Tuanudom, S. Suradhat, L. Vimolket, Y. Poovorawan, R. Thanawongnuwech, A. Amonsin, P. Kitikoon); and Mahidol University, Nakhon Pathom, Thailand (S. Tantawet)

Suggested citation for this article

Abstract
A swine influenza outbreak occurred on a commercial pig farm in Thailand. Outbreak investigation indicated that pigs were co-infected with pandemic (H1N1) 2009 virus and seasonal influenza (H1N1) viruses. No evidence of gene reassortment or pig-to-human transmission of pandemic (H1N1) 2009 virus was found during the outbreak.

In April 2009, a novel swine origin influenza A (H1N1) virus, now referred to as pandemic (H1N1) 2009 virus, emerged in humans in Mexico and the United States and spread worldwide (1). In May 2009, pandemic (H1N1) 2009 was confirmed in 2 patients in Thailand who had a history of travel to Mexico. Shortly after the emergence of this virus, reports of transmission from humans to pigs on pig farms were documented (2,3). Human-to-pig transmission of this virus was reported in Thailand on December 17, 2009 (www.dld.go.th/dcontrol/Alert/Ah1n1/H1N1%20update22_12_2009.pdf). Pigs showed mild respiratory signs; only 1 pandemic (H1N1) 2009 virus was isolated from 80 nasal swab specimens.


Swine influenza virus (SIV) was reported in Thailand in 1981 (4). All 3 subtypes (H1N1, H3N2, and H1N2) of this virus are circulating in Thailand (5). A recent pathogenesis study demonstrated that subtype H1N1 induces typical SIV-like illness and slightly more severe gross lesions than illness induced by subtype H3N2 (6). Genetic data indicate that SIV (H1N1) in Thailand differs from pandemic (H1N1) 2009 virus. SIV (H1N1) in Thailand contains surface proteins of influenza viruses from North America and Eurasia, which are also found in pandemic (H1N1) 2009 virus; SIV (H1N1) in Thailand contains internal proteins of viruses from Eurasia; and pandemic (H1N1) 2009 viruses contain swine, human, and avian virus gene segments (5,7).

We report an outbreak of infection with pandemic (H1N1) 2009 virus during November 2009–March 2010 on a commercial pig farm in Thailand. The outbreak presumably resulted from human-to-pig transmission because 1 of the workers on this farm had influenza-like clinical signs at the beginning of the outbreak. Infection in this worker was not confirmed because he quit his job on the farm after the start of the outbreak and could not be located.

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Pandemic (H1N1) 2009 Virus on Swine Farm, Thailand, Table 1 | CDC EID

Suggested Citation for this Article
Sreta D, Tantawet S, Na Ayudhya SN, Thontiravong A, Wongphatcharachai M, Lapkuntod J, et al. Pandemic (H1N1) 2009 virus on commercial swine farm, Thailand. Emerg Infect Dis [serial on the Internet]. 2010 Oct [date cited]. http://www.cdc.gov/EID/content/16/10/1587.htm

DOI: 10.3201/eid1610.100665


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Address for correspondence: Pravina Kitikoon, Faculty of Veterinary Science, Chulalongkorn University, Henri-Dunant Rd, Pathumwan, Bangkok 10330, Thailand; email: pravina21@gmail.com