OFFLU animal influenza report: February 2019-September 2019

Authors: Anderson, Tavis; ARENDSEE, ZEBULUN - Orise Fellow; CHANG, JENNIFER - Orise Fellow; KIMBLE, BRIAN - Orise Fellow; KUNZLER-SOUZA, CARINE - Orise Fellow; BROWN, IAN - Animal And Plant Health Inspection Service (APHIS); ESSEN, STEVE - Animal And Plant Health Inspection Service (APHIS); COLINS, SUSAN - Animal And Plant Health Inspection Service (APHIS); LEWIS, NICOLA - Royal Veterinary College; Baker, Amy; VENKATESH, DIVYA - Royal Veterinary College

Submitted to: World Health Organization
Publication Type: Government Publication
Publication Acceptance Date: 9/24/2019
Publication Date: 9/27/2019
Citation: Anderson, T.K., Arendsee, Z., Chang, J., Kimble, B., Kunzler-Souza, C., Brown, I., Essen, S., Colins, S., Lewis, N., Vincent, A.L., Venkatesh, D. 2019. OFFLU animal influenza report: February 2019-September 2019. World Health Organization. p. 1-7.

Interpretive Summary:

Technical Abstract: Epidemiologic and phylogenetic analyses of influenza A viruses (IAV) provide rational criteria for vaccine strain selection, control strategies, and may identify viruses with pandemic potential. From the 1918 human influenza pandemic to date, human-to-swine interspecies influenza A virus (IAV) transmission events have repeatedly occurred, some leading to sustained transmission and increased IAV diversity in pig populations. These swine IAV have the potential to be introduced back into the human population if they are substantially different from current human seasonal strains. We quantified the global genetic diversity of swine IAV circulating from 2016 to present, and the genetic diversity of swine IAV in the USA over the past 6 months. We determined how similar the circulating swine IAV diversity was to human IAV vaccines and current candidate vaccine viruses (CVV) that are used in pandemic preparedness efforts. We also antigenically characterized a subset of viruses or CVV strains in hemagglutination inhibition (HI) assasys. These data demonstrated that the tested swine IAV was significantly different to teh current H1 and H3 components of human IAV vaccines. Additionally, only 7 of the 29 distinct genetic clades detected in swine globally are covered by CVV strains; and the degree to which those CVVs provide protection is dubious given observed genetic differences. We present a comprehensive picture of IAVs infecting swine and how this diversity varies between regions. These analyses demonstrate the dynamic interplay of IAV transmission between humans and swine, and identify genetic groups that should be considered in vaccine strain selection for pandemic preparedness. Testing additional viruses in HI assays with human sera will provide an assessment of human population immunity and quantify the pandemic potential of these swine H1 and H3 viruses.