Novel Zoonotic Avian Influenza A(H3N8) Virus in Chicken, Hong Kong, China

Abstract

Zoonotic and pandemic influenza continue to pose threats to global public health. Pandemics arise when novel influenza A viruses, derived in whole or in part from animal or avian influenza viruses, adapt to transmit efficiently in a human population that has little population immunity to contain its onward transmission. Viruses of previous pandemic concern, such as influenza A(H7N9), arose from influenza A(H9N2) viruses established in domestic poultry acquiring a hemagglutinin and neuraminidase from influenza A viruses of aquatic waterfowl. We report a novel influenza A(H3N8) virus in chicken that has emerged in a similar manner and that has been recently reported to cause zoonotic disease. Although they are H3 subtype, these avian viruses are antigenically distant from contemporary human influenza A(H3N2) viruses, and there is little cross-reactive immunity in the human population. It is essential to heighten surveillance for these avian A(H3N8) viruses in poultry and in humans.

Keywords: Avian influenza virus; China; H3N8; Hong Kong; chicken; emergence; human; immunity; influenza; influenza virus; novel; population; respiratory infections; serology; viruses; zoonoses.

Figure

Phylogenetic analysis of influenza A(H3N8) viruses isolated from chicken farms, live poultry markets, and the Mai Po Wetlands, Hong Kong, China (bold). A) Hemagglutinin gene segment; B) neuraminidase gene segment; C) polymerase basic 2 gene segments. Strains listed in Table 5 were analyzed with other relevant virus sequence data available in public databases (accession numbers in Appendix Table). Trees were generated by using IQ-tree (https://www.iqtree.org) with the general time reversible plus gamma model. Bootstrap values >80% are shown. Scale bars indicate estimated genetic distances.