LAUSR

Abstract Since the first outbreak of avian influenza A(H7N9) virus in China in early 2013, several interventions to control the transmission of H7N9 virus from poultry to humans have been implemented. Temporarily closing live poultry markets reduced the risk of human infection to an extent, but it did not prevent the spread of the H7N9 virus among poultry, and this spread eventually led to more human cases. Nevertheless, the mass vaccination of poultry after September 2017 has been highly effective in preventing the H7N9 virus infection in both poultry and humans. In light of the emergence of highly pathogenic H7N9 and H7N2 viruses in unimmunized ducks, vaccination among poultry, especially for ducks, should be accompanied with continued surveillance of H7N9 variants and other avian influenza A viruses that could signal a heightened pandemic risk.