Evolution of H3 avian influenza virus in China: Implications for pandemic preparedness

A high prevalence of the H3 subtype avian influenza virus (AIV) has been observed among waterfowl globally. It causes asymptomatic or mildly symptomatic infection in birds. In addition, a high cross-species transmission ability makes the virus a potential source for the origination of other animal influenza viruses. The first human case of AIV infection (H3N8) was detected in China in April 2022. The patient was present with recurrent fever and severe pneumonia. The second case with mild influenza symptoms was detected in May 2022. These cases raised global concern about the possibility of a significant public health threat by H3N8 AIVs.