Current State of Knowledge on Highly Pathogenic Avian Influenza

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Aquatic birds are the natural hosts of type A influenza viruses. Influenza viruses are categorized by the glycoprotein spikes on their surface – the ‘HA’ or haemagglutinin protein (16 different subtypes identified so far) and the ‘NA’ or neuraminidase protein (nine subtypes). All 16 HA and nine NA subtypes (see box on Terminology) have been detected in various combinations in aquatic wild birds, and for the most part these viruses live harmoniously with their natural hosts, establishing a short-lived subclinical enteric infection (Webster and Hulse, 2004). Occasionally, viruses cross from aquatic wild birds to poultry or mammals, and new genotypes of virus may become established in these non-natural or spillover hosts. Once adapted to non-avian hosts, these viruses may lose the capacity to multiply in the gut of aquatic birds (Kobasa et al, 2001)

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تاریخ انتشار 2008