page_title: Influenza A virus subtype H9N2
section_title: Infection in birds
hierarchical_section_title: Influenza A virus subtype H9N2 / Infection in birds
caption_attribution_description: English: H9N2-type influenza A viruses donate their internal genes to other IAVs. Recent studies revealed the contribution of the internal genes of H9N2 in the genesis of various, recently evolved AIV strains with zoonotic potential [135,138,139]. Poultry (chicken pictogram) served as mixing hosts for emergence of these influenza reassortants, which are then transmitted naturally to humans (human pictogram), or evaluated experimentally in ferrets (ferret pictogram), leading to infections/deaths.
context_page_description: Influenza A virus subtype H9N2 is a subtype of the species Influenza A virus.
  Over the years the H9N2 influenza strain caused illness in several children aged nine months to 5 years in Hong Kong with the latest occurring in December 2009.
context_section_description: H9N2 is the most common subtype of influenza viruses in Chinese chickens and thus causes great economic loss for the poultry industry, even under the long-term vaccination programs. Recent human infections with avian influenza virus revealed that H9N2 is the gene donor for H7N9 and H10N8 viruses that are infecting humans too. The crucial role of H9N2 viruses due to the wide host range, adaptation to both poultry and mammals and extensive gene reassortment. In China, which is regarded as a breeding ground of avian influenza viruses, the H9N2 virus has been detected in multiple avian species, including chicken, duck, quail, pheasant, partridge, pigeon, silky chicken, chukar and egret.
  Epidemiological and genetic studies revealed that the hemagglutinin (HA) gene of the H9N2 influenza viruses could be divided into Eurasian avian and American avian lineages. The Eurasian avian lineage involved three distinct lineages, including A/chicken/Beijing/1/94-like (BJ/94-like), A/quail/Hong Kong/G1/97-like (G1-like), and A/duck/Hong Kong/Y439/97 (Y439-like).
caption: H9N2-type influenza A viruses donate their internal genes to other influenza A virus subtypes
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