H9N2 subtype influenza viruses have become endemic in various types of terrestrial poultry in Eurasian and African countries and have caused sporadic infections in humans and mammals. China is regarded as the epidemic center of H9N2 viruses.
In China, H9N2 subtype avian influenza outbreak is firstly reported in Guangdong province in 1992. Subsequently, the disease spreads into vast majority regions nationwide and has currently become endemic there. Over vicennial genetic evolution, the viral pathogenicity and transmissibility have showed an increasing trend as year goes by, posing serious threat to poultry industry.
H9N2 has demonstrated significance to public health as it could not only directly infect mankind, but also donate partial or even whole cassette of internal genes to generate novel human-lethal reassortants like H5N1, H7N9, H10N8 and H5N6 viruses.
Min Gu. Current situation of H9N2 subtype avian influenza in China. Gu et al. Vet Res.2017
Chong Li. Genetic evolution of influenza H9N2 viruses isolated from various hosts in China from 1994 to 2013. Emerging Microbes & Infections .2017
Trushar Jeevan. A(H9N2) influenza viruses associated with chicken mortality in outbreaks in Algeria 2017. Influenza Other Respi Viruses. 2019