H9N2 Subtype Avian Influenza Viruses in China: Current Advances and Future Perspectives
H9N2 Subtype Avian Influenza Viruses in China: Current Advances and Future Perspectives
Hanqin Shen1,3, Boliang Wu1,2, Guangwei Li1, Feng Chen1, Qingbin Luo1,3, Yimin Chen1, Qingmei Xie1,2,3*
ABSTRACT
The H9N2 subtype avian influenza virus (H9N2 AIV), which has been in circulation for two decades, has become the predominant subtype in China, attracting considerable attention due to human infections and the contribution of internal genes to H5N1 and H7N9 influenza viruses. Multiple H9N2 AIV genotypes have been identified from various species, including birds and mammals. H9N2 AIVs could spread through water, air, and live bird markets. Since the first isolate from 1994 in China, H9N2 AIVs have been prevalent over 20 areas of China, especially in South China, such as Guangdong, Guangxi, and Fujian provinces. Vaccination is the predominant strategy to prevent and control H9N2 AIVs. There are three inactivated vaccines of H9N2 AIVs have been used in domestic poultry in China. But H9N2 AIVs occurred frequently and caused severe economic losses to the poultry industries. H9N2 AIVs can evade the pressure of vaccination by genetic evolution and antigen variation. Moreover, the ratio of L226 in the haemagglutin (HA) receptor binding site has increased, which indicates that the H9N2 virus has the increasing potential to infection and cause human epidemics. The threat to the poultry industry and public health should not be ignored. In this review, we summarised the findings of recent studies on H9N2 AIVs epidemics and strategies for their prevention in poultry in China.
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