A H9N2 altípusú madárinfluenza-vírus növekvő jelentősége a világban - Irodalmi összefoglaló
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The low pathogenic avian influenza (LPAI) H9N2 subtype is the most widespread avian influenza virus globally nowadays. Major wild bird migration routes and livebird markets at certain regions certainly contributed to the successful spread of this subtype. Since the ‘90s, the virus has become endemic in poultry and there is an increase in the number of countries being constantly affected through the horizontal spread among the poultry farms. As LPAI H9N2 is not a notifiable disease the knowledge on the distribution and prevalence of the disease in domestic and wild bird populations remains limited in European countries. While H9N2 LPAI is not recognised to cause significant animal health concerns in European countries thanks to high sanitary standards, cases are sporadically reported. It causes serious animal health problems and associated economic losses in other regions such as Middle East, Northern Africa and Asia due to less advanced biosecurity, husbandry and sanitary systems and a combination of infectious diseases and climatic conditions that are enhancing the pathogenicity of H9N2 field strains. Beyond the damages H9N2 causes to poultry industry it presents a zoonotic threat, not only itself, but by providing the so-called internal genes to other subtypes, e.g., H5N1 and H7N9 AIVs, which caused lethal infection in humans. It is also known that H9N2 provide internal genes for other subtypes of AIV, notably intersubtype reassortants between H9 and H5. Co-circulation of H5N1 and H9N2 viruses in poultry farms and live bird markets increases the risk of human exposure, raising concerns for potential emergence of new influenza A pandemic viruses. Despite the fact, that infections caused by LPAI H9N2 are not notifiable but, considering the zoonotic potential, significant economic losses, and propensity for reassortment, surely there is a need for increased vigilance and a regular monitoring of the situation. In this review paper the authors would like to summarise the present knowledge on LPAI H9N2.