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Title: Reverse zoonosis of influenza to swine: new perspectives on the human–animal interface

item NELSON, MARTHA - Fogarty International Center
item Baker, Amy

Submitted to: Trends in Microbiology
Publication Type: Review Article
Publication Acceptance Date: 1/4/2015
Publication Date: 3/1/2015
Citation: Nelson, M.I., Vincent, A.L. 2015. Reverse zoonosis of influenza to swine: new perspectives on the human–animal interface. Trends in Microbiology. 23(3):142-153.

Interpretive Summary: The genetic diversity of influenza A viruses circulating in swine has expanded greatly since 2009, presenting new threats to human health. The evolution of viral diversity in swine frequently is attributed to high-density commercial swine production systems where rapid turnover and movement of animals allows for multiple viral lineages to co-circulate and reassort. Recently, enhanced surveillance has identified the most important original source for influenza virus diversity in swine: humans. Human-to-swine transmission of influenza viruses occurs far more frequently than swine-to-human, and is central in seeding swine populations globally with new viral diversity. Overcoming the bias towards viewing swine more as sources of human viruses than as recipients is key to accurately understanding the human-animal interface and the role of humans in the evolution of pandemic viruses in swine.

Technical Abstract: The origins of the 2009 influenza A (H1N1) pandemic in swine are unknown, highlighting gaps in our understanding of influenza A virus (IAV) ecology and evolution. We review how recently strengthened influenza virus surveillance in pigs has revealed that influenza virus transmission from humans to swine is far more frequent than swine-to-human zoonosis, and is central in seeding swine globally with new viral diversity. The scale of global human-to-swine transmission represents the largest 'reverse zoonosis' of a pathogen documented to date. Overcoming the bias towards perceiving swine as sources of human viruses, rather than recipients, is key to understanding how the bidirectional nature of the human-animal interface produces influenza threats to both hosts.