Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 2/11/2004
Publication Date: 3/8/2004
Citation: Spackman, E. 2004. Bird flu to human flu: type a influenza and host specificity. Meeting Abstract. Interpretive Summary:
Technical Abstract: Although type A influenza has a broad host range in birds and mammals, the natural hosts of the virus are wild waterfowl and shorebirds. Host restriction of individual influenza isolates has been attributed to the affinity of the hemagglutinin (HA) protein, which binds the host cell receptor, sialic acid residues, to bind either '2-3 or '2-6 linkages, which have different distributions in different species. Outbreaks of H5, H7 and H9 influenza subtypes in humans, which are genetically avian isolates, in Hong Kong, Viet Nam, Thailand and the Netherlands, demonstrate that host specificity is not as tightly regulated by the sialic acid linkage affinity as previously thought. Interestingly, many of the avian isolates which have been transmitted to humans have been highly pathogenic (HPAI) in chickens, although there is no clear relationship between an isolate being HPAI in chickens and the ability of the isolate to be transmitted directly to humans or with virulence in humans. The HA protein also regulates pathogenicity in chickens, but not in mammals or even other avian species. Work at SEPRL with H5N1 HPAI influenza isolates has further demonstrated that virulence and host specificity are not solely regulated by the HA protein as virulence and replication ability of isolates with the same H5 HA vary among both avian and mammalian species.