Recent studies in this journal revealed that some H7N9 viruses reassorted with duck AIVs, and then attained the ability to efficiently infect ducks.1,2 H7N9 AIVs have been endemic in chicken since their emergence in China in February 2013.3 After its emergence, H7N9 viruses have evolved substantially, and have frequently reassorted, acquiring internal genes from other chicken H9N2 viruses, increasing the genetic diversity of H7N9 viruses.4 This raises the concern that whether H7N9 can attain internal genes from other AIVs.