| Popis: |
Wild aquatic birds are natural hosts for a large variety of influenza A viruses. Occasionally, viruses are transmitted from this reservoir to other species, such as chickens, pigs, and man, and may then cause devastating outbreaks in domestic poultry or give rise to human influenza pandemics. The H5N1-, H7N7-, H9N2-, and H2N2-viruses are considered to have high pandemic potential, because of their pathogenicity in humans and because of the lack of immune protection in the human population. However, the unexpected outbreak of the H1N1 pandemic in 2009 demonstrates that the reliability of such predictions is limited. Host specificity, pathogenicity, and transmissibility are polygenic traits that depend on the interactions of viral proteins with host factors, among which receptor specificity and fusion activity of the hemagglutinin, nuclear transport of the polymerase, and interferon antagonism of the NS1 protein are of particular importance. |
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