Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2012 Sep;6(5):348-57.
doi: 10.1111/j.1750-2659.2011.00324.x. Epub 2011 Dec 30.

Transmission of pandemic influenza H1N1 (2009) in Vietnamese swine in 2009-2010

Karen Trevennec  1 , Lucas Leger, Faouzi Lyazrhi, Eugénie Baudon, Chung Yan Cheung, François Roger, Malik Peiris, Jean-Michel Garcia
Affiliations

Transmission of pandemic influenza H1N1 (2009) in Vietnamese swine in 2009-2010

Karen Trevennec et al. Influenza Other Respir Viruses. 2012 Sep.

Abstract

Background: The pandemic of 2009 was caused by an H1N1 (H1N1pdm) virus of swine origin. This pandemic virus has repeatedly infected swine through reverse zoonosis, although the extent of such infection in swine remains unclear.

Objective: This study targets small and commercial pig producers in North Vietnam, in order to estimate the extent of H1N1pdm infection in swine and to identify the risk factors of infection.

Methods: Virologic and serologic surveillance of swine was carried out in 2009-2010 in pig farms (38 swabs and 1732 sera) and at a pig slaughterhouse (710 swabs and 459 sera) in North Vietnam. The sera were screened using a influenza type A-reactive ELISA assay, and positive sera were tested using hemagglutination inhibition tests for antibody to a panel of H1-subtype viruses representing pandemic (H1N1) 2009 (H1N1pdm), triple reassortant (TRIG), classical swine (CS), and Eurasian avian-like (EA) swine lineages. Farm-level risk factors were identified using a zero-inflated negative binomial model.

Results: We found a maximal seroprevalence of H1N1pdm of 55·6% [95% CI: 38·1-72·1] in the slaughterhouse at the end of December 2009, 2 weeks after the peak of reported human fatalities with H1N1pdm. Farm-level seroprevalence was 29% [95% CI: 23·2-35·7]. In seropositive farms, within-herd seroprevalence ranged from 10 to 100%. We identified an increased risk of infection for farms that specialized in fattening and a decreased risk of infection in farms hiring external swine workers.

Conclusions: Our findings suggest extensive reverse-zoonotic transmission from humans to pigs with subsequent onward transmission within pig herds.

PubMed Disclaimer

Figures

Figure 1
Figure 1
(A) Pig and (B) Human densities in North Vietnam. (C) Seroprevalence of H1 pandemic in provinces of origin of pigs collected in Hanoi slaughterhouse from October 2009 to May 2010 and human fatal cases during the 2009/2010 epidemic (from September 2009 to February 2010).
Figure 2
Figure 2
Serological distribution of samples from (A) slaughterhouse or (B) farm in the Red River Delta during the winter 2009–2010.
Figure 3
Figure 3
Seroprevalence swine influenza H1 all subtypes and H1N1pdm spreading in pigs collected in Hanoi slaughterhouse from October 2009 to May 2010 and monthly incidence of fatal cases in human in Vietnam.
Figure 4
Figure 4
Location of seropositive farms for H1N1pdm (cross‐sectional survey in the Red River Delta, winter 2009–2010).
See this image and copyright information in PMC

References

    1. Garten RJ, Davis CT, Russell CA et al. Antigenic and genetic characteristics of swine‐origin 2009 A(H1N1) influenza viruses circulating in humans. Science 2009; 325:197–201.2. - PMC - PubMed
    1. Smith GJ, Vijaykrishna D, Bahl J et al. Origins and evolutionary genomics of the 2009 swine‐origin H1N1 influenza A epidemic. Nature 2009; 459:1122–1125. - PubMed
    1. Hancock K, Veguilla V, Lu X et al. Cross‐reactive antibody responses to the 2009 pandemic H1N1 influenza virus. N Engl J Med 2009; 361:1945–1952. - PubMed
    1. Vijaykrishna D, Poon LL, Zhu HC et al. Reassortment of pandemic H1N1/2009 influenza A virus in swine. Science 2010; 328:1529. - PMC - PubMed
    1. Pereda A, Rimondi A, Cappuccio J et al. Evidence of reassortment of pandemic H1N1 influenza virus in swine in Argentina: are we facing the expansion of potential epicenters of influenza emergence? Influenza Other Respi Viruses 2011; 5:409–412. - PMC - PubMed

Publication types

MeSH terms

Substances