Evolutionary analyses show that H7 influenza viruses probably transferred from ducks to chickens in China on at least two independent occasions, and that reassortment with H9N2 viruses generated the H7N9 outbreak lineage that recently emerged in humans in China, and a related previously unrecognized H7N7 lineage; these H7N7 viruses are shown to have the ability to infect ferrets, and the current pandemic threat could extend beyond H7N9 viruses.
- Tommy Tsan-Yuk Lam
- Jia Wang
- Yi Guan