Pandemic (H1N1) 2009 Virus on Commercial Swine Farm, Thailand

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.

Genetic characterization of influenza virus circulating in Brazilian pigs during 2009 and 2010 reveals a high prevalence of the pandemic H1N1 subtype

“…The observation that most of the human‐ and swine‐derived isolates appear to have originated from human‐derived isolates is also consistent with a higher frequency of human‐to‐human and human‐to‐swine transmission compared with zoonotic swine‐to‐human transmission 15. Indeed, reports on the 2009 pandemic outbreak suggest that the virus evolved silently in the swine host until its introduction to the human population,32 after which it disseminated rapidly among humans and frequently spilled over from humans to pigs 14. Although in line with other reports, the relationships displayed in the dendrograms should be interpreted carefully.…”

Retrospective swine influenza serological surveillance in the four highest pig density provinces of Thailand before the introduction of the 2009 pandemic Influenza A virus subtype H1N1 using various antibody detection assays

“…It should be noted that pH1N1 emerged in Thai pigs in late 2009, 31 and the current seroprofile of the Thai SIVs could possibly be different from the current study.…”

“…7,9,17,22,28,32,37,42 Similarly, cocirculation of both pH1N1 and endemic Thai swine H1N1 viruses was found in the same farm with no reassortant virus. 31 However, a novel reassortant virus could possibly emerge without notice. Based on intensive surveillance, the pandemic reassortant virus was demonstrated in Thailand.…”

“…Thai SIV subtype H1 can be further divided into 3 clusters (clusters I-III). 30,31,34 Therefore, whole genome characterization of previous and current Thai SIV isolates is necessary because it could provide essential epidemiologic data and diagnostic and disease preparedness of the current viruses. Currently in Thailand, there are only 16 whole genomes of 2000-2005 (6 H1N1, 9 H3N2, and 1 H1N2), 8 H1N1 whole genomes of 2009-2010, 20,31,34 and 38 HA genes available in the public database.…”

“…34 Data published in 2010 showed that the pandemic H1N1 2009 (pH1N1) virus is now circulating in Thai swine herds. 31 It should be noted that before the introduction of pH1N1 in Thailand, SIV HI test antigens and serological data had not yet been evaluated. The objectives of the current study were 1) to genetically characterize the hemagglutinin (HA) gene of Thai H1 and H3 SIV field isolates; 2) to establish H1 and H3 HI test antigens by investigating cross-reactivity among the Thai H1 and H3 SIV isolates; 3) to use the established HI test for swine sera evaluation collected from the 4 highest pig density provinces of Thailand; and 4) to compare the findings of the established HI test with the SIV commercial enzyme-linked immunosorbent assay (ELISA) kits for H1-and H3-specific antibody detection.…”