Abstract

The H5N1 and H9N2 subtypes of the avian influenza virus (AIV), part of the Orthomyxoviridae family, induce one of the most severe zoonotic diseases. The harmful impacts of H5 and H9 avian influenza viruses can affect avian and mammalian species, including human health, and result in economic loss and public health hazards. It has been isolated from several avian species and humans throughout all continents, except Antarctica. The incidence of avian influenza fluctuates based on regional and temporal variables of various avian species and humans. The AIV subtypes are categorized into low-pathogenic and high-pathogenic according to their virulence. H9N2 was classified as low pathogenic, whereas H5N1 was deemed highly pathogenic. Molecular diagnostic tests, such as real-time polymerase chain reaction and conventional polymerase chain reaction, are used to identify avian influenza viruses. The most common serological tests, such as enzyme-linked immunosorbent assay and hemagglutinin inhibition, are used to detect antibodies against influenza A and B viruses. AIV subtypes and host species affect the severity, clinical manifestations, and fatality rates of AIVs. Avian and swine infections are the primary vectors for the transmission of AIV to humans, presenting a considerable public health risk. An adequate surveillance system, a robust vaccination approach, and a segregation and culling protocol for avian influenza-infected birds are urgently required to eliminate avian influenza viruses. This comprehensive study provides a framework for understanding the risks associated with AIV subtypes H5 and H9. The goal is to avoid and control the disease, as it can spread into a major pandemic.

Key words: Epidemiology; Influenza virus; PCR; Public health; Zoonotic disease.