Increased risk of A(H1N1)pdm09 influenza infection in UK pig industry workers compared to a general population cohort

the Combating Swine Influenza (COSI) Consortium; the Flu Watch Group; Fragaszy, Ellen; Ishola, David A.; Brown, Ian H.; Enstone, Joanne; Nguyen-Van-Tam, Jonathan S.; Simons, Robin; Tucker, Alexander W.; Wieland, Barbara; Williamson, Susanna M.; Hayward, Andrew C.; Wood, James L.N.

Abstract

Background: Pigs are mixing vessels for influenza viral reassortment but the extent of influenza transmission between swine and humans is not well understood.

Objectives: To assess whether occupational exposure to pigs is a risk factor for human infection with human and swine-adapted influenza viruses.

Methods: UK pig industry workers were frequency-matched on age, region, sampling month, and gender with a community-based comparison group from the Flu Watch study. HI assays quantified antibodies for swine and human A(H1) and A(H3) influenza viruses (titres?40 considered seropositive and indicative of infection). Virus-specific associations between seropositivity and occupational pig exposure were examined using multivariable regression models adjusted for vaccination. Pigs on the same farms were also tested for seropositivity.

Results: 42% of pigs were seropositive to A(H1N1)pdm09. Pig industry workers showed evidence of increased odds of A(H1N1)pdm09 seropositivity compared to the comparison group, albeit with wide confidence intervals (CI), Adjusted Odds Ratio after accounting for possible cross reactivity with other swine A(H1) viruses (aOR) 25.30, 95% CI [1.44-536.34], p=0.028.

Conclusion: The results indicate that A(H1N1)pdm09 virus was common in UK pigs during the pandemic and subsequent period of human A(H1N1)pdm09 circulation, and occupational exposure to pigs was a risk factor for human infection. Influenza immunization of pig industry workers may reduce transmission and the potential for virus reassortment.

• Journal Article Type: Article
• Acceptance Date: Nov 9, 2015
• Online Publication Date: Jan 29, 2016
• Publication Date: Jan 29, 2016
• Deposit Date: Jun 29, 2016
• Publicly Available Date: Jun 29, 2016
• Journal: Influenza and Other Respiratory Viruses
• Print ISSN: 1750-2640
• Electronic ISSN: 1750-2659
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 10
• Issue: 4
• Pages: 291-300
• DOI: https://doi.org/10.1111/irv.12364
• Keywords: Humans, influenza, occupational exposure, serology, swine; zoonoses
• Public URL: https://nottingham-repository.worktribe.com/output/771350
• Publisher URL: http://onlinelibrary.wiley.com/doi/10.1111/irv.12364/abstract
• Related Public URLs: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4910179/