In Pakistan, H9N2 avian influenza viruses were first reported in 1998, and since then, they have been prevalent in chickens and have continuously evolved through reassortment in live bird markets. Poultry carrying H9N2 viruses act as incubators for the evolution of influenza viruses in wild birds. Recent reports have shown that the Pakistani H9N2 viruses have undergone antigenic drift and evolved into novel genotypes posing a potential threat to poultry and human health having genome segments similar to H5N1 and H7N3 viruses. Recent evidence of interspecies transmission suggested that the H9N2 avian virus could be the next human pandemic strain. Continuous monitoring of viral evolution and updates on vaccines are warranted to achieve efficient control and eradication of H9N2 viruses in Pakistan. The following review covers the emergence and evolution of H9N2 viruses and vaccination strategy in Pakistan.
