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Factors responsible for the continuous persistence and evolution of low pathogenic avian influenza virus (H9N2)

  • M. UMER ASHRAF (a1), M. SHAHID MAHMOOD (a1), A. RAFIQUE (a2), R. ZAHID ABBAS (a3), Z. IQBAL (a3), M. YOUNAS (a4), S. AHMAD SADIQ (a1), M. USMAN (a1), M. OMER ASGHAR (a1) and M. USMAN ISHAQ (a1)...


Avian influenza virus (AIV) type A subtype H9N2 usually causes mild asymptomatic infections, and is mostly undetected and is, therefore, under-reported. This has allowed the virus to rapidly evolve via mutations and reassortments in its genome with other avian influenza subtypes especially H1N1, H5N1 and H7N3 thereby introducing new variant strains and producing severe disease. It has been reported that the AIV H9N2 donated its internal genes for the devastating 1997 Hong Kong outbreak and furthermore, it may be the cause of the next influenza pandemic. There are many factors such as its wide host range, ability to cross the species barrier, ecological diversity, antiviral resistance and zoonotic importance that make it an excellent candidate for the next influenza pandemic. These and other factors like ineffective vaccination, negative immunological pressures, lack of surveillance, which contribute to its continuous persistence and evolutionary dynamics are discussed in this paper. It is important to take the necessary measures to control and prevent its unchecked circulation to prevent the future outbreaks.


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